Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: ra on November 15, 2001, 08:47:00 PM
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The glass stab needs to be fixed. I hardly ever see P-38's but when I do 2 pings and the stab goes bye-bye. Then the P-38 dance starts: nose pitches up, bellybutton over teakettle, pissed off pilot firing tracers all over the place all the way down to the ground.
More people would fly these things if the stab was held on by something more than duct tape.
ra
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the 38 is the only plane that cant dare to HO a C202. It will lose its stab.
But wait, no other planes have the glass tail problem.. lets just ignore it. :rolleyes:
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Didn't notice a tail weakness in the P38 Wild Wednesday....
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Had a good look at one a couple of weeks ago. I could wrap my arms around the tail boom. That thing is skinny. Sure looks flimsy.
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Heh Seeker. Thats because OTHER 38's were shooting at it (nose package doesnt seem to have the increased punch from being in nose imo). :D
You're right funked, its thin, but hardly flimsy. It is the weakest part of the plane. But its *amazing* how bullets hit it with such astounding regularity. Not to mention that most non-cannon rounds would just go through it without ripping it. But hey, even a .303 in AH does the job in a ping. *shrug*
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When I fight a P38, I usually try to hose the tail, saw it in half :D
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Originally posted by funkedup:
I could wrap my arms around the tail boom. That thing is skinny. Sure looks flimsy.
That is odd, everybody keeps saying how big it is and that is why it is so easy to hit :)
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Originally posted by bolillo_loco:
That is odd, everybody keeps saying how big it is and that is why it is so easy to hit :)
That is because they don't know what they are talking about. Funny thing is real pilots from W.W.II and statistic both say the back half of the P-38 was hard to hit. Most, if not all flight sims model the P-38 as a billboard with a bullet magnet for a frame. They make it too easy to hit, and too easy to see. For the truth about the P-38, see the articles at C.C. Jordan's website, "Planes and Pilots of World War II", especially the one entitled "The P-38, is Size and Shape a Disadvantage?" But don't expect anything to change, it's just one of the handicaps that P_38 pilots in sims have to deal with. Oh, and if you've ever seen pictures of what happens to a P-38 in an overspeed dive when compression tries to tear it apart, you'll have even more respect for the toughness of the rear half of a P-38.
Renegade Savage
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Yep. Many pilots came home with the plane's rivets POPPED OUT from the high-g's... One of the leading aces even came back with his tail booms BENT more than 10 degrees from the g-forces.
Overspeed? Heh, why dont you get a P-38 in AH to 30k+ and powerdive the WHOLE way down in a 90 degree dive with WEP on.. you will never ever break 510 mph. The plane will NOT shed wings. Mainly because it WONT go past 510. The 38 would actually go to near 600mph (with high risk of structural failure), but that wasnt a very popular thing to try ;).
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I think that people are very suceptible to stab failure because there is only 1. In the P47, when I loose the stab with 2-3 pings it doesn't bother me that much because I can still fly around. If it was a P38, I would be pissed because it would mean death.
The P38 stab is not more fragile than any other plane but it's the one you notice because there is only one.
that's my thoughts :)
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Frenchy,
You may be getting the stab mixed up with the elevator. I don't think any planes in AH fly with a stab shot off. It just seems like the stab of the P-38 is a bullet magnet, and the plane is very easy to kill. Roughly 3 out of 4 P-38's I've killed were stab kills.
ra
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Every airplane in the MA loses it's stab from time-to-time. This is probably the weakest point on the P-38 (given it's structure over-all), but this is one VERY large airplane. I don't hesitate to attack a P-38 when flying the 262, because I know I can hit it. I'm not so sure of any other fighter, except perhaps the Mozzie.
And, too, when you hear one ping in AH I believe you are actually getting hit with a lot of rounds. Especially, when the gun firing at you is a .50 caliber.
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HO a C202 in a 38 Voss. You will lose half the times if the C202 is shooting at you aiming for your nose. The darts it shoots hit the tail stab and whack it off.
The problem is AH's all or nothing damage model. If you think about it, the 38's stab is BIG..but its also ATTACHED to both tails. You can punch big holes or even CUT the stab at any point, the Stab will STILL be there. In AH, any kind of damage rips off the ENTIRE thing (and the irony of it is that once that happens, the 38 flips on itself, giving the pissed off pilot a nice view of his own stab, the WHOLE stab flapping and falling over him!).
I'm more inclined to say that the P-38 TAIL BOOMS were the real weak point of the plane, and it would take a DAMN good hit from MG fire or a CANNON hit to rip it off... and hey, cutting ONE of the tails in half did not guarantee that the entire tail would blow out. There was a P-38 in the Med. that collided with a 109 and had its left tail boom snapped..but the plane made it home because the OTHER tail held in place.
I would ask HTC to MODEL the 38's damage so that EACH tail has its own damage model and the STAB have 2 separate damage models.
Thus, if one tail is hit, depending on how serious it is, it would either break that ONE tail (and make the 38 as hard to keep control of as when you lose a wingtip) or lose control of that tail's rudder (and quite possibly LOSE control of the stab?). The stab should be broken into 2 areas for the damage model.. half of it tied to 1 tail, the other tied to the other tail. Thus, if I get hit on the left side of the stab and it gets shot out, the other half of the stab will still be there (and of course, the associated severe loss of control on the plane because you lost half a stab).
But heck, regardless, im sure everyone agrees the all-or-nothing damage model royally SUCKS.
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I've been recently flying the P38 practicing for my role in the "Big Week" and am liking this plane. In my view, the person named "38" seems to make a pretty good point in his post and I think it is something worth considering.
I do have one question though, and that is I'm wondering if AH roll rates are influenced by torque? That is, do the single engine aircraft roll faster one side vs the other? I recently read how in the Pacific the P38s would generally roll right if an enemy got on his tail because the Japanese planes rolled much slower in that direction due to torque which was something the P38's were not subject to due to counter rotating props.
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I too think the tail section on the P-38 is awfully easy to knock off... too easy.
I'd like to see a more detailed damage model for ALL the aircraft and vehicles but perhaps the present one is so deeply embedded into the programming that this is what we're going to have to live with.
Still, they've shown they can make small changes to the model. I'd say the P-38 tail section deserves another look.
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The P-38 suffers from no torque thanks to its counter-rotating props. The Zero, just like any other plane without c-rotating props, does roll better to a side thanks to its Torque. US pilots learned that the zero could not manouver well at high speeds, and a favourite tactic used against it was high speed manouvers. The F4U Corsair, if in trouble, would merely nose down and dive away from the Zero.
The Zero, like the 109 and F4U , is "harder" to turn to one side because of the torque. The F4U, having a better high speed handling than the zeke (who's controls were very slugish above 300mp or so), would get above 300mph with the zeke on its tail and TURN to the right (using your example, I dont remember which side it was).. a turn the zeke would not be able to follow, allowing the Corsair to escape.
In AH the roll rate is influenced by Torque. Get a 109G10 reaaal slow and WEP it. You will feel the torque.. it takes a lot more pulling the stick to make the plane bank to one side. The La-7 also has this. The N1k is the only plane I dont see as having a torque effect for such a monster engine.
-Tac
(this is my out-of-home bbs account..no way in heck am I leaving me bbs info on U. systems)
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Ra, my bad, I thought u were talking about the Stabilator of the P38. You where indeed talking about the vertical stabilizator?
(or maybe the P38 doesn't have a stabilizator, it's an elevator? :D ).
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Tac or any other P38 nut,
I am interested in hearing any tips on fighting the P38 vs the 190 and 109. Until last night, wasn't too nervous about them but one guy I encountered in a 190 handed my twin-booms to me and sent me packing. I just started flying the P38 this month and am interested in hearing tips from those who have experience.
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Frenchy,
I was just using 'stab' as short for horizontal stabilizer. The P-38 doesn't have a stabilator, it has a horizontal stabilizer and an elevator. When the stab gets shot off the elevator goes with it.
P-38's are rare in AH, but when you do see one there is a good chance you will soon see it toppling end over end with nothing left between the tailbooms. It is an Achille's heel the P-38 didn't have.
ra
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There must be a glitch somewhere with the 38 i remember gettin both tails blown clean off by an ost and the thing was flying smooth even when I turned......hell I even landed it.....with one flap gone..........don't raise a fuss I don't want that, but thats just what happened....this was with patch 5null (http://null) (http://www.geocities.com/chico_styln/fadedglory.jpg)
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The 109/190 are the easiest planes to kill when you in a 38. You can out-turn the later models and you can keep up with anything the earlier models do...except dive (when, or should I say IF HTC decides to fix the dive flaps, they wont be able to pull that either!. 5+ tours waiting for this and counting) and top speed.
Force them into sciscors or turnfights. You'll eat them easy. Best when you low alt, so the cowardly waffles dont dive to momma's ack.
Dont zoom up with a g10 or d9 (you recognize them because the dont turn as much and zoom up reeeeal fast). Dont dive following a 190. You can follow a 109 on a dive, but only if you are inside d300 range.. if he's d500+ and dives, he's gone.
Stay above them in any situation. If they dive away, you stay level or do a slight dive to get speed...and watch them. In the MA someone else will dive after them and make them turn or zoom climb to evade ..and thats when you dive on them, as they go up.Many 109's and 190's dive away, see you at d4.0, think they are safe and zoom up to re-engage... and they dont realize that the d4.0 is because of alt separation, not horizontal.. ive seen many waffles climb up and find me at d300 range in 2 seconds...and i'd be at 400mph while they will be at 250mph from climbing.
The 38 should never follow a 109 and 190 in dive (IF the dive flaps were fixed you could try, but you'd still lose as the 109/190 fly at 500'ish and retain that E much, much longer than you ever will.. and you will have burned your alt and your E for nothing). As a general rule. See the above for an exception with the 109's.
If you fighting above 25k, remember your fowler flaps give you a great turning ability.
[ 11-28-2001: Message edited by: 38 ]
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I figured vs a 190 the last thing you'd want to do is try to scissor him due to his fast roll rate.
I did recently come across some variant of 109 at low altitude and tried to circle fight and the guy kept right on my six and even damaged me a bit before I was able to get away.
How do you generally get the fight to slow down when you need that?
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The more a 190 rolls when losing speed, the deeper he digs his grave. 190's will hardly go past 1 or 2 sciscors. You out-accel them, so if you cut engine to half during the top part of sciscors (bottom part, full wep to regain E) and the 190 TRIES to keep up, it will kill itself, they either stall or disengageOf course, this is when you try and shoot them.
Puke, I said the 38 can keep UP with the earlier models in turns.If you got out-turned by a g10 or a d9, you were not using flaps or had something hanging from your plane :p. The P38 can keep up with the 109 and 190 in turns..because it turns a tad better and accels MUCH better than they do (except a g10 on wep)... if you cloverleaf (pull some g's on the turn, then stop pulling while WEP to regain a bit of E, pulling again..with use of flaps of course) them you get many shots into them If the 109 is on your 6, you wont shake him off by doing a circle fight. That's what sciscors and spiral dives are for *G*. To get them slow? Ermm.. I think your best bet will be to lure them into turning.. and turning. Again, remember that all i've said so far is when they are coming at you from 6 oc AND have alt/e adv.
Many of them bite the hook.. the 38 is so big, so porked and generally so poorly flown in the MA that they go straight in and follow you into any manouver...like sciscors or turns. When I see a 109 or 190 NOT get into turns, but instead dive away and keep his speed higher than mine, I know the guy knows the 109 and 190. I can even ID who's on the plane... Fester LOVES to do 90 degree dives on his 190 and then pull up, fart and climb to my 6. I hate him. Very much :D
[ 11-28-2001: Message edited by: 38 ]
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P-38s catch rounds very nicely. My Wurger likes to eat them very much.
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I thought the P-38 got a bit tougher in 1.08. Maybe just my imagination.
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I've made some durability changes to the P-38 for the next patch.
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Originally posted by 38:
If you fighting above 25k, remember your fowler flaps give you a great turning ability.
Well, the P-38 of the AH might do that but the real P-38 losed it's maneuverability at high altitude due to comressebility. The combat flaps helped at low altitude and at low speeds.
gripen
[ 11-28-2001: Message edited by: gripen ]
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wooohooo pyro!! :)
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Thanks Pyro! Hey, while I got you here, did you get that 5 meg e-mail with info about the dive flaps I sent about a month ago?? Yea or nay only thing I ask :)
Gripen, wrong. The 38 suffered from compresibility, but that has nothing to do with the flaps. 38 flaps had a lock which would NOT allow them to deploy past 250mph (early 38's ripped their flaps off when pilots did not retract them). The plane compresses at 410-420 mph up high.
However, the plane indicated 250 mph, but its real speed easily was 350, near 400 (redline indicator). So in reality it would gain great manouverability at normal combat speeds. The late 38J's and L versions took care of the compression problem in combat with the dive flaps. Pilots were then able to enter compression without the danger of locking up until they hit thicker air... and their dive flaps PULLED the nose UP at 3 or 4 g's if they were deployed when the plane was compressed (if deployed before it would let the pilot pull the nose up..sort of like what AH has now). I just wish the AH 38 had the 3-4g after-compression nose up effect (which is the 5 megs I sent Pyroman :D ) .
"I thought the P-38 got a bit tougher in 1.08. Maybe just my imagination"
The single-ping engine death problem plaguing many planes was fixed. The reason why you grazed a 38 and killed it in earlier versions was because you'd blow the tail off or kill both engines in one whack. The tail seems to have been toughened up a bit (I mean the Tail Booms), but the stab is still removed by a couple .303's.
[ 11-28-2001: Message edited by: Tac ]
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Just a question for '38'. How do you think the anti-compressibility flaps are broken in the AH P-38? Just curious as to what you think is wrong with them.
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Read above sundog. AH dive flaps only do half of what they should do.
The dive flaps had TWO distinct effects depending at what point they are deployed.
If the dive flaps were deployed before the dive or before the plane reached a high speed (above 350?) it would prevent the "tuck under" effect and allow the pilot to pull the nose up, albeit slowly. This the AH dive flaps do (although trimming elevator up pulls nose twice as fast... odd).
If the dive flaps were deployed after the plane compressed it would pull the nose up all by itself, at about 3 to 4 g's. Test pilots even said that if left alone, with no input from the pilot, they would pull a neat loop by itself. In combat, the 38 using the dive flaps after compression was able to recover from a high speed dive and pull out VERY quickly... something the german fighters couldn't follow...and many augered.
This last effect, the most important effect, is not present in AH.
This is part of the 5-meg info I sent Pyro some time ago. Its a page from Hangar Flying, a magazine issued to P-38 pilots during the war, written by the test pilots back in the states to inform deployed pilots of the capabilities of the plane and the what-nots. This page says part of the info on the dive flaps, specifically on the part that's absent in AH.
(http://home.cfl.rr.com/wraithfleethq/diveflps3.jpg)
[ 11-28-2001: Message edited by: Tac ]
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Tac if the plane has the dive flaps down with a given altitude, airspeed, attitude, angle of attack, and power setting, it shouldn't make a bit of difference whether the flaps were deployed before or after the dive was started. To make a plane that behaves like you say, HTC would have to violate the laws of physics that govern the flight model.
The only explanation is that in the first of the two cases you describe, the pilots had trimmed the plane for the dive.
[ 11-28-2001: Message edited by: funkedup ]
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Im no aeronatical enginerdeer funked, but I think the airflow change caused by the flaps being deployed at the speeds, along with the change of center of gravity cause that. Again, this is just my guess. All I know is that it happened.
See the pic above. I cant resize it without becoming illegible.
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The 38 is fine the way it is. If it does get so-called "fixed", what are ya gona complain about then?
The guns are bad!
Dosen't turn good!
Wheels don't go around fast enough!
Canopy gets stuck!
Turbo-chargers dont activate at the right alt!
The wing tips are too fragile!!
The airspeed indicator is off .32% at 560mph!
I got a complaint! Pyro, yesterday my little 109F4 received a 6 second burst from a Mossie and my wing fell off! WTF! I thought the wing was more sturdy than that! Could you fix it??
Have a Nice Day! :)
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And the hellfire tastes like saltwater! Damn these brit breweries!!!!!
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Thx for the pic Tac. It's quite legible for me. Nice job on research.
I still think it must have been trim. If you started with the flaps deployed you would probably trim the plane into the dive in that condition, and it would not pitch up as noticeably. If you started with flaps up and trimmed the plane into the dive in that condition, then you would notice a bigger change when you changed the configuration by popping the flaps out.
I'll try to test fly tonight, to see if what I say can be duplicated in AH.
[ 11-28-2001: Message edited by: funkedup ]
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Tac,
Well, just take your P-38 manual and look compressebility table, at 30k the P-38 was limited to bit over 3g at any speed. The P-38 turned about as well as the P-47 at high altitude (above 20k) and the P-51 could out turn them both. At low altitude (below 10k) and at low speed (around 140mph IAS) the P-38 could out turn the P-51 with combat flaps.
Your dive flap information is also somewhat incomplete. The dive flaps gave about 3g automatic pull out at 10k but at 30k they gave just 1g.
gripen
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Gripen, the 38 out-turns both when its fowlers are deployed. At what speed was your info taken?
"Well, just take your P-38 manual and look compressebility table, at 30k the P-38 was limited to bit over 3g at any speed"
compressibility and how many g's it can pull on level flight.. what's the relationship? I think that info may be incorrect. Wish Widewing was here. :p
"Your dive flap information is also somewhat incomplete. The dive flaps gave about 3g automatic pull out at 10k but at 30k they gave just 1g."
Again, at what speed? Where are you getting this info? If its true, then LW planes couldnt pull a single G at that alt when they followed a 38 on high speed dives. That mustve been nice, not blacking out when attacking bomber formations.. that sounds kinda odd dont you think?
[ 11-28-2001: Message edited by: Tac ]
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Tac,
The compressebility table of the P-38 is actually the flight envelopes of the p-38, you can find similar stuff for the P-47 from Nikla's documents and the manual of the F4U-5 contains similar data for the F4U. There exists USAF test data about this, the P-51 out turned the P-38 at high altitude. And the reason for this was simply the better compressebility characters of the P-51, actually at high speeds the P-51 could even out turn the Spitfire at high altitude for this same reason.
About dive flaps I have test flight data, at 10k and at mach 0,67 the dive flaps gave about 3g and at 30k and mach 0,67 they gave 1,2g (centre of gravity was at aft limit).
gripen
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Gripen can you scan that flight test data? G vs. altitude at constant Mach would be interesting. I assume they fixed the yoke in the same position and used the same pitch trim setting for all tests? Or did they trim for 1g flight at each Mach/altitude combination? If that information is included then HTC would be able to quite accurately figure out the pitching moment coefficient for the dive flaps.
[ 11-28-2001: Message edited by: funkedup ]
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Well, I find it odd. The 38 was only outperformed by the p51 at high speeds..at lower speed the 38 beat the crap outta the pony. Same for the jug.
Dunno. Just sounds odd to me.
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funkedup,
I have no scanner but you can find this same data from the PRO (RAE TN Aero 1702) there is also some NACA documents in PDF format in their server which explain well how these devices worked (can't remember numbers now) IIRC I have claimed those documents in the usenet discussions with CC/Widewing (try coogle). IIRC there was an article in the Niklas's documents page which shows how effectivenes of the dive brakes decreased when altitude raised.
gripen
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Tac,
Well, don't believe me. There exists a lot USAF, RAF, NACA and RAE test data about the P-38 around and if you put some effort on searching you can check all this yourself.
gripen
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Originally posted by Pyro:
I've made some durability changes to the P-38 for the next patch.
WOOOOOOOOT WOOOOOOOOOOT WOOOOOOOOOOOT! Hell I thought the last patch changed it making it a tougher ride. Cool beans.
xBAT
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I have no problem believing the P-51D out turned most planes (especially a P-38J/L) at airspeeds over 300+ mph IAS at any altitude, however considering the P-51D's power to weight ratio, especially at higher altitudes, it had to bleed speed quickly not? I could be wrong and I only offer questions and there seem to be some very knowledgable people and I enjoy the reading.
turning ability and climbing ablility at altitudes over 20,000ft. the P-38J/L had a lot better power to weight ratio at these altitudes than did the P-51D, isnt that important for bleeding speed? also what was the condition of the P-51D? The few tests I have seen where the P-51D/B are used always use a specially conditioned air frame and the rear tank empty and or removed from the P-51B/D making it light at take off while the other planes take off at full weight. So the tests that I have seen (and I have not seen them all) usually favor the P-51 series. Thanks guys and just curious I enjoy the reading like I said earlier.
[ 12-01-2001: Message edited by: bolillo_loco ]
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bolillo_loco,
You can see from the flight envelope of the P-38 that the ability to sustain gs drops throughout (IAS) speed range while the altitude increases. But for example in the case of the P-47 the ability to sustain gs stays constant at low (IAS) speeds when altitude increases (so far I have not found a reliable flight envelope for the P-51). Also effectivenes of the combat flaps decreases with altitude because Clmax decreases when altitude increases. The turbos give a theoretical advantage keeping power constant up to the critical altitude but in the case of the P-38 this benefit is partially lost because propeller blade tip speeds are quite high (just look speed curve of the P-38, the speed starts to drop below critical altitude, rammed or unrammed). Also the P-51 was very well streamlined and able to keep it's energy level up during maneuvers.
There are a lot unfair comparisons on WWII fighters but IMHO it's the P-51 which suffers most in these comparisons. The P-51 had a pretty good range even without fuselage tank, better than early P-38 or P-47, much better than P-40, P-39 or P-63. Also the P-51B performed somewhat better than later D model. Generally the P-38 climbed better than the P-51 at normal ratings, but the difference is not so great as some comparisons indicate, main difference is that the P-38 could climb at high angle and slow speed (good for spiral climb). Actually the P-51B-1 (67") outclimbed the P-38J-1 (60") in the USAF test (also outdived, outrolled, outturned at all altitudes without combat flaps, zoom climbed better from the dive, maintained speed longer after dive, outrun and even out accelerated at level flight after initial stage where the P-38 was better).
gripen
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"outdived"
Of course. But the P-38 will outdive it initially due to its higher accel, but only initially.
"outrolled"
duh, what doesn't? :)
"outturned at all altitudes without combat flaps"
Exactly. Without combat flaps. Above 250mph the p51 eats the 38 in turns. Below that, the 38 eats the pony.
"zoom climbed better from the dive"
Perhaps it from a 500mph+ dive.
"maintained speed longer after dive"
Of course, the pony retains far more E than the 38 ever will
"outrun"
I thought that was the pony's main strength. Of course :D
"and even out accelerated at level flight after initial stage where the P-38 was better"
Define intitial stage. The p38 will reach from 0 to 200 mph far faster than the p51. After 200mph the p51 will accel a tad faster thanks to its airframe. That is why a slow (200mph or less) pony has no chance in hell against a P-38 unless it dives to run away.
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Just thought id remind you that the term 'forked tailed devils' was invented and used by the LW transport aircraft in the mediteranean theatre :)
They was not called devils by the fighters.In fact Galland actually said he prefered to fight them to any other allied fighter.
Yes they were good aircraft but they were never considered the best air to air fighter the allies had.
Now you have a flying tank it seems.It is far tougher to shoot down now than almost any other plane ive attacked since the patch and Ive flown them and taken almost an entire loadout of bullets from a spitfire.Lost flaps,gear 1 engine fuel tanks rudders ailerons but it just kept flying.
I was in agreement the tail was a little weak but it seems pyro has made the ENTIRE aircraft tough as old boots now.
And one thing i would like to say is this...
when Ive questioned performance or durability etc of any LW plane in the past I get mostly abuse and the old 'AH has it modelled "by the numbers" and it is therefore correct' (gun issue) or that we must have proof or documents to ask for changes.
Well if the 'numbers' were all correct how was the p38 wrong? I agree it didnt FEEL right getting your tail blown off so easy but i had no evedence to SHOW US just HOW wrong it may be.I also called for a bit of toughening of the P38 but now I want to know how this degree of toughening was done BY THE NUMBERS?.Were the numbers for armour wrong? was it a bullet calculation problem? a bug in the software?
If they are going to decide which plane is correct by how they feel/number of complaints/questions, then compare to what we can all read about them then there is a problem looming I fear.
I think pyro has no data in this area right? its all down to what HTC decide is right in this area, I assume they calculate armour thickness/penetration of bullets/explosive power structural strengh? how durable area hit is?.Well somewhere along the line it becomes a guess-timate right? As it is too many complaints and they up the durability a touch? I hope not but suspect this must be how its done.If this is so Im not going to listen to this SHOW US THE EVIDENCE crap anymore i can tell you! :D
I want to take this oppertunity to re-mention the well known fact that the P51 was very susceptable to (even) light calibre ground fire.You guys notice that when you fly it?
I dont, but i sure do in other planes that i thought or read were tough to bring down.
As the p38 issue has been adjusted could HTC PLEASE give us the parameters they use to DECIDE which aircraft is 'right' for durability?
btw although this may sound like an attack it isnt.I merely want to know how this was all decided.Lets not pretend any longer that if someone feels something is wrong he may very well be right?? and not a WHINER??
god i hate that word ;)
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Tac,
The USAF test results are quite clear, the P-51B had the better acceleration in the dive. Theoretically we can argue forever about how dive entering method (zero g or what ever) affects to the results. About combat flaps you have still some things to learn, those can be used up to 250mph IAS but they really gave advantage at much lower speed, around 140mph and below. The combat flaps also wasted energy and in fact there are claims using them might put a plane tactically bad low energy situation. The effectivenes of the combat flaps decreased when the altitude raised and the P-51 could outturn the P-38 at high altitude by using flaps. In the zoom climb from cruising speed the P-38 and the P-51 were equall, from the dive the P-51 was superior. For the definition of the acceleration you should consult USAF documents, anyway I quess we are not interested what happens between 0-150mph. Generally the P-51 could do pretty much everything better than the P-38 above 25k specially if it keeped speed up. Generally I tend to wonder those claims about benefits of the P-38 at low speeds, it could turn well then but ailerons were really slow (normal or boosted).
hazed,
IIRC the USAF made somekind of study about vulnerability of those planes, it was based on interviews of the shot down pilots and statistics. The results were something like that the P-47 was best and the P-51 and the P-38 were about equall. Anyway, there has been some discussion about the term "forked tail devil", but so far noone has come out with clear evidence who invented it. Some Germans certainly used it during war but among the Luftwaffe the P-38 was allways known as the Lightning.
gripen
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hazed, i agree with you with that the 38 is quite durable now. but think about it. its a flying wing for all that matters. If you hit the wing section (which is where most hits land), you're either taking out the wingtips or hitting the big 'ole engines.
Most 38's I see out there have smoking engines because of that. Mostly again, cuased by MG fire (cannon birds kill the engine or break the 38's wing off).
Wingtip loss is another very common damage in the 38, as well as aleiron and flap damage...well, you're hitting the big 'ole wing.
Now compare that to a P-47. You can literally PUMP 400 rnds of .50 at the fuselage of a jug and it'll take it. But if you hit its wings, its gone. The 109 also takes a good deal of damage on fuselage, so does the spit. But again, hit their wings and they go down. A p38 has no fuselage to speak of (and if you hit the cockpit, you kill the pilot), and its wings are very strong as they hold the engines.
Yet, I kill other 38's just as easy as I kill any other plane, it takes a few good pings in one place. I was used to spraying at a 38 , watching 3 or 4 flashes and watch it break apart, now I see it take those flashes and start smoking up, lose parts of the wings, etc. a few more pings and it goes down.
And this is with mg's. The 190a5 I flew last night wacked 38's left and right with a few hits.. with the 4X20mm loadout.
I'd say its about right now. next on list is dive flaps and all will be well. :)
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This is a pretty interesting thread. :)
If that test showing the P-51B outclimbing the P-38J is the same one I've come across, it also states that the P-51B climbed at 3,900 fpm at sea level, which is far and away the highest figure I've ever seen for it. Curiously, the same report quoted the P-51's military climb rate as only 2,500 fpm.
About the combat flaps--P-38 pilots on Guadalcanal, at least, found them at times useful well above 250 mph in combat. No indication whether the 250 mph lock was removed in the field or simply never fitted. (Of course, the drag penalty of flaps, even Fowlers, at 300+ mph would be considerable.)
One big plus for P-51s in actual combat seems to have been the introduction of the K-14 lead-computing gunsight (fitted to many P-51s as well as late-model P-47s, can't find any reference to it ever being used on P-38s). It apparently made a big difference in gunnery accuracy.
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Guppy,
Yeah, it's the same one and couple writers have quoted this same report in their books (J.Ethell and K. Delve). Actually if you dug a bit, you can find even better numbers for the P-51:
Mustang III 4700fpm +25lbs grade 150 fuel(Rolls Royce test)
Mustang IV 4500fpm +25lbs grade 150 fuel (A&AEE)
Mustang I 4090fpm 60" (A&AEE, F4R, 8200lbs)
About combat flaps I stated that those gave advantage (over the P-51) at slow speed, flaps certainly helped at higher speeds too. The speed limit is IAS speed and it's probably a structural limit. At high altitude and high speed use of combat flaps probably caused compressebility effects due to high Clmax.
gripen
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The P-51B had only four 50 caliber machine guns, slightly less armor, and did not have the 85 gallon fuel tank in the fuselage behind the cockpit. No doubt it was light and climbed well. But it had less than adequate armor, armament, and range.
The P-51 NEVER had a range advantage over a contemporary P-38, EVER. Especially not on internal fuel.
No, the P-38 was never equipped with the gyroscopically stabilized lead computing gunsight. Just like it was never equipped with the Hamilton Standard prop.
The P-38 was clearly superior to the P-51 at altitudes of over 30K feet. With a much lower stall speed, a much better turn rate at lower air speeds, and a clear power advantage at high altitude.
Critical Mach is just that, critical Mach. Other than a limit of handling at high speeds, it means nothing. Critical Mach means only that at or above that speed, the plane no longer responds to control input, and is therefore incapable of controlled flight. It does not affect handling at altitude, other than peak controllable speed.
As a matter of fact, the P-51 was known to spin out of fights at higher altitudes, and to do it more often than the P-38.
The P-38J-15-Lo had boosted ailerons and was able to roll faster than the P-51 above 325 MPH.
The P-38J and later at normal power would out climb the P-51D at military power, and the distance between the two at WEP was even greater.
The P-38L was faster than the P-51D at altitudes above 25K feet. The P-38J was faster than the P-38L.
The power curve of the Merlin in the P-51D began to level off and then turn downward as altitude increased over 18K feet while the Allison with its turbocharger actually had as good or better power even up to 28K feet.
Try using something other than just USAAF test data, as it was notoriously incorrect and biased.
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Wow, 1 whole week with a deem pc crash... and i am finally back. I am looking into new pc this weekend... so i am waiting to download the game onto it. Ok... back to the topic.. I agree with tac. you guys that are saying p38 does not outturn a jug/51 may be a little mentally challenged ;).. how often do you fly p38. I am one of the worst pilots in p38.... and even I can outturn those planes with it. It just takes brains to do it, which spitfire pilots ect.. do not have. Go fly p38 nonstop for awhile, and you should find it pretty darn easy to turn with those planes.. AND 109's and MAYBE a n1k... they are not as much a threat to p38 after 1.08. Well, happy flying... hope to see you all in the air real soon.
Lazer
=375th=
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lazer good to see ya. They're talking about the real 38 here if you hadnt noticed ;)
P38 faster than 51D at high alts? uh-uh. Nope.
"The P-51 NEVER had a range advantage over a contemporary P-38, EVER. Especially not on internal fuel"
Huh? Pony on full internal fuel had
more range than the 38 on internal.
[ 12-04-2001: Message edited by: Tac ]
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Wow Gripen, I didn't know they tried a Basta Mustang! I'd love to fly the Spit VIII with that motor. :)
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thank you for the explanation gripen, does a web page exist that shows this flight envelope data? something like the naca web site? I would like to see the condition of the P-51 in question.
The mustang to my knowledge for example was out climbed by the P-47D-40 and D-40 and all versions of the P-38H and later. The 3,475fpm (for the P-51D) initial and higher figures are always taken from mustangs that are 1,000 plus lbs lighter at take off and then compaired to max rate of climb for the 38 and 47 taking off under max weight no external stores. not a fair compairison. same can be said for the max g load. I have seen usaf charts that list max g load, but the mustang's weight is only 8,000 lbs.
again interesting reading could somebody point me out to some ulrs and or books which state this.
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Originally posted by hazed-:
Lets not pretend any longer that if someone feels something is wrong he may very well be right?? and not a WHINER??
god i hate that word ;)
Sung to the theme from 'Flipper'...
They call him Luftwhine! Luftwhine!
Whines about lightnings,
No-one you see,
Complains more than he!
And we know Luftwhine, message board poster
Flying for Fuhrer,
Cries to HT!
[ 12-05-2001: Message edited by: Montezuma ]
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Ah yes Montezuma to the rescue to spread his euphoric sense of stupidity.
I think the 38 has been fixed to a point of perk? :) J/K I like it now. It needed the fix and I hope others are looked into as well.
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Mustang III 4700fpm +25lbs grade 150 fuel(Rolls Royce test)
Mustang IV 4500fpm +25lbs grade 150 fuel (A&AEE)
Mustang I 4090fpm 60" (A&AEE, F4R, 8200lbs)
I've come across the first two figures before. The climb rates are about 1,000 fpm above the normally accepted climb rates, which is quite consistent with similar RAF tests on Spitfires with 150 grade fuel.
The 8,200 lb. Mustang I is over a thousand pounds lighter than a Merlin Mustang without fuselage tank. Were it heavier by that much (10-15%), its climb rate would most likely be somewhere in the mid-3,000 fpm area.
The tests I've seen consistently show the P-38 at around 3,800 fpm plus or minus 100 fpm or so. In my opinion, the balance of evidence is that the P-51B/D was in the 3,500 fpm class. The gap seems to widen on military power--3,200 fpm for the P-38J/L vs. 2,500 fpm for the P-51B/D.
I agree the flap IAS limit was probably a structural limit. However, in at least one case this was exceeded by 100 mph without trouble, and some pilots felt quite free to exceed the limit by a fair margin. (Whether this would make you popular with your maintenance crew is unrecorded. :))
[ 12-05-2001: Message edited by: Guppy ]
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Renegade Savage,
Generally the P-51 without fuselage tank had longer range than the P-38 without leading edge tanks (production models before J-15). With those tanks the P-51 still had a better range. It can be argued that the P-38 could cruise very long time at low RPM and high MAP but that was not practical in the ETO. One of main tactical advantages of the P-51 was ability to cruise fast (high energy level) at combat area.
Turning performance issues are discused above, the P-38 had gentle stall, noone has argued otherwise.
Find a manual to understand compressebility issue under g load and this same thing is described in the "America's Hundred Thousand" too.
Those boosted ailerons were introduced in the J-25 and at high altitude the P-38 could not safely do more than 290mph IAS so there the P-51 had advantage in the hole speed range. It should be also noted that boosted ailerons did not solve slow acceleration of the roll which was a conceptual problem.
Comparing just hp values without counting exhaust thrust and propeller efficiency is not fair. Besides the V-1650-3 in the P-51B had rammed critical WEP altitude about 27k (29k according to some sources).
Please show us less incorrect and less biased data than USAF tests.
Funked_up,
Actually the RAF did not just tested but also used grade 100/150 fuel in their Mustangs for the V1 hunt.
bolillo_loco,
The P-51B-1 in the USAF test weighed "approximately 9000lbs", in the RAF and RR test weighs were equall or above 9000lbs (except in the case of the Mustang I). The P-51D climbed some 200-300fpm slower than the P-51B due to higher weight and higher drag.
Generally I see the tests I have quoted quite reliable, the P-51 was loaded for similar or longer range than other planes in the comparison.
You can easily find books by Ethell or Delve but there are excellent archives around like the PRO or the NARA, you don't have to rely on books...
Guppy,
I agree your point about the Mustang I, normal combat load was around 8600lbs and also the F4R was very rare on the Mustang.
As I have noted above, generally the P-38 climbed better than the P-51 but the difference is not very large if both planes are loaded for a similar mission. And I mostly agree with your numbers except in the case of the P-51B which climbed a bit better than the P-51D, around 3600-3750fpm on WEP.
gripen
[ 12-05-2001: Message edited by: gripen ]
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A few hundred feet per minute in climb rate isn't a massive difference, true, but it is something. The fighters of 8th AF didn't generally have to scramble to altitude to defend their own bases, so it probably didn't matter that much to them.
As for range, the last air victories of 13th AF were claimed over Singapore by P-38s; http://www.enter.net/~rocketeer/13thfacts.html (http://www.enter.net/~rocketeer/13thfacts.html) states that the Lightnings in question were based in the Phillippines, a round-trip distance of over 2,000 mi. Of course, this required 300 gal. drop tanks and superb air discipline. The large tanks were not used in the ETO, and it would be hard to maintain a precision cruise while flying over heavily defended parts of Europe.
To be fair, the IAS restrictions on both planes with altitude were as follows:
P-38:
10,000 ft: 420 mph
20,000 ft: 360 mph
30,000 ft: 290 mph
(Dive flaps were estimated to add an extra 20 mph to the above.)
P-51:
0 ft: 505 mph
10,000 ft: 480 mph
20,000 ft: 400 mph
30,000 ft: 300 mph
I did get the impression that the limits imposed on the P-51 had more to do with structural integrity (shedding wings in a hard pullout) than compressibility, though.
One P-38 ace who went on to fly the P-51 for some years postwar stated that he thought the Lightning was better below 20,000 ft and the Mustang above 20,000 ft; from the available evidence, I'm inclined to go with that.
By the way, does anyone know of any flight evaluations done with the P-82 (F-82) Twin Mustang? I'm curious as to what its initial roll response was like, given its configuration.
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"I think the 38 has been fixed to a point of perk? J/K I like it now. It needed the fix and I hope others are looked into as well"
Give me a 38F/H/J , fix the dive flaps on the L and you can make the 38L a cheap 4pnt perk plane... IF the 51D, La7, 190D9 and 109G10 get perked likewise :)
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Gubby,
Not much to comment about the rest but the IAS limits varied somewhat between the models, for example the P-51B had following restrictions:
35k 298mph
30k 336mph
25k 376mph
20k 422mph
15k 468mph
10k 520mph
But it should be noted that going above limiting speeds with the Mustang was not as fatal as it was with the P-38. Buffeting started around mach 0,75 but under test conditions the P-51 reached mach 0,86 and still under control. In the case of the P-38 buffeting and tuck under started around mach 0,67 with or without dive flaps and became increasingly stronger above this speed. The dive flaps gave positive pitch making recovery possible at somewhat faster speed than without them and also added a lot of drag but even with flaps speeds over mach 0,7 were very dangerous.
gripen
[ 12-05-2001: Message edited by: gripen ]
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Hehe..TAC is sneaky. The J is faster AND lighter as it doesnt have quite the fuel load of the L...
xBAT
P.S. Yea a GREEN 38 would be nice.
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"jumping on the p-38 bandwagon"
Correction:
Although it was suggested by developers, the name "bandwagon" was never officially given to the p38, fortunately they decided on the more menacing sounding "lightening" . Just thought I'd clear that up .
[ 12-05-2001: Message edited by: Suave1 ]
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Generally is a rather broad term. Excluding proper fuel management is not really a good basis for the comparison either.
The USAAF data almost always shows the Mustang being tested at less than full combat weight, especially the later models with more guns, armor, and fuel. Empty the 85 gallon fuselage tank behind the cockpit and you have a different plane. Around 600# of weight in a bad place for the center of gravity changes the whole flight envelope.
The first P-38J, the J-1-Lo had 65 gallon leading edge tanks, the later versions had from 110 up to 160 gallon leading edge tanks.
As to flying for fuel economy, the speed of the P-38 was not greatly reduced when flying at 50" of pressure at 2200 RPM in auto lean, and it could cruise at the same speed as the P-51. Using the Lindberg method was out of the question in the ETO, since he specified auto lean, 55" of manifold pressure, and 1600 RPM. The only problem with using the first method is that you had to be able to throttle up without looking, and to know when to do it. If you had to look at the throttles, prop and mixture controls, and had to be told when to throttle up, you were in trouble. The P-51 was easier to fly in that respect. But there was no great disparity in cruise speeds, and if you had to fly with the bombers, then the bombers were the limit anyway.
Also loaded out for the same mission, the P-38 could climb out towards enemy territory directly, where as the P-51 required you either reach enemy territory with lower altitude, or burn fuel circling while you climbed.
To quote Captain Arthur Heiden 20th FG 8th USAAF, "You could reach cruise altitude from England before landfall in a P-38, while in the P-51, you still had considerable climbing left to do." I'd prefer to arrive to the fight at altitude and speed, with plenty of internal fuel left to fight and go home.
At its critical altitude of of 26,900 feet, the P-51D had a top speed of 437MPH, while the P-38J-25-Lo had a top speed of 414 MPH. At 30,000 feet, the speed roles were reversed, with the P-38 at 412, and the P-51 at 404. At 35,000 feet, they were no closer, at 389 for the P-38, and 378 for the P-51. At 40,000 feet the P-38 was at 348 MPH, while the P-51 was at... just over 37,000 feet. These compare true air speeds at WEP, 67" of manifold pressure for the P-51, and 64" for the P-38. The P-51 had neither the lift nor the power of the P-38 at very high altitudes, but the better prop carried it up okay.
The advantage of the P-38 was two fold. the turbocharger gave it a decided power advantage at altitudes of 30,000 feet or higher, and the high aspect ratio wing gave it more lift at low speed and at high altitude in the thin air.
The Merlin was always a great engine in the altitude range it was tuned for. The single drawback of a strictly mechanical supercharger compared to a turbocharger is that it is tied directly to engine speed, and is incapable of compensating for changes in altitude beyond a very specific range. that is why there were several versions of the Spitfire that had only engine changes, their engines were tuned for certain altitude ranges.
The thinner laminar flow wing of the P-51 gave it a decided edge in speed and drag, but it had less lift, which hurt lower speed handling and also hurt the climb rate.
Nothing is free. the high aspect ratio wing of the P-38 gave it lift, fuel capacity, low speed handling, and climb, but at the price of drag, and it was the wing that caused compression. Kelly Johnson always admired the Spitfire wing profile, but the Spitfire never had the range afforded by the internal wing tanks.
The first thing done to the P-38 to combat compression was to increase the radius at the joint between the wings and the center nacelle. They had wanted to further increase that radius, along with moving the leading edge at the center nacelle forward, thereby increasing the sweep, and add two or three more degrees of dihedral to the wing section. But any really serious development geared towards major air frame changes was dropped after the P-38K was cancelled.
You are correct, the P-38 had no exhaust thrust boost, nor did it have any ram effect, except for a field modification never factory nor Lockheed approved, but used none the less. The GE B2,B33, and B34 turbochargers did not like the backpressure resulting form the fitting of an exhaust hood designed to produce exhaust thrust. There was no gain from the radiator exhaust either.
You are also correct that the Curtiss prop on the P-38 sucked. It is indeed a testament to the Allison that it was able to power the plane so well despite the props. It should be noted that Lockheed requested that they be allowed to fit the Hamilton Standard prop to the P-38. The USAAF and War Production Board considered the P-38 to be so critical to the war effort that the estimated production stoppage of 7-10 days was out of the question. The USAAF supplied the Curtiss prop in 1939, and required Lockheed to use it, and while they allowed nearly every other fighter to be fitted with the Hamilton Standard prop, the P-38 was never afforded that advantage.
A good comparison can be made by looking at the P-51K, which was fitted with a version of the Curtiss prop. The P-51K lagged some 25-40 MPH behind the P-51D in top speed, and some 600 FPM in rate of climb.
Witness the P-38K, AKA the P-38 that never was. With just the Hamilton Standard prop, it was faster at all altitudes than the P-51D. It also had a rate of climb superior to any U.S. fighter. The increase in efficiency from the prop resulted in a 10-15% increase in range.
I'm in complete agreement that exceeding critical Mach in a P-38 was more dangerous than in any other plane save the P-47, and it was a close race there. of the U.S. planes, the P-51 probably did as well or better than any when critical Mach was exceeded.
I also agree that between 20,000 feet and 27,000 feet, at speeds above 300 MPH, the P-51 held some decided advantages in both turn and roll rate, along with a measurable advantage in engine performance relating to top speed. The advantages the P-38 held were climb rate, turn rate below 275 MPH, and acceleration below 350 MPH.
Below 20,000 feet, and above 30,000 feet the P-38 was a better ride.
That being said, knowing half a dozen real World War II pilots who flew the P-51, the P-38, and the P-47, from what they've told me, I'd prefer to be in the P-38, as it was a better all around performer at most speeds and altitudes. I'll give up a little advantage at certain speeds and altitudes in order to gain better all around performance at a wider range of speeds and altitudes.
The truth is, it's the guy with the yoke or stick in his hands that makes the difference. Among the U.S. planes, the P-38 was like a Ferrari or a Corvette, it was a killer in the hands of a dedicated expert, but would get an uninitiated kid in deep trouble.
There is considerable data on the P/F-82. The engines in it were actually designed for the P-38, and fitted with turbochargers would have made considerably more power than even the P-38L engines, but the Curtiss prop could never harness the power.
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*drool*
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Speaking of P-38's....what's up with all the P-38s at 40k in the MA lately?
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Originally posted by Tac:
*drool*
And you're drooling over? Or you think I'm drooling?
I wish I had decent frame rates, I'd be flying instead of arguing in these discussions. But my frame rates too ka huge hit with the latest patch. Sixteen FPS at best and 10 FPS average with a drop to 4 FPS isn't uncommon.
[ 12-05-2001: Message edited by: Renegade Savage ]
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The numbers I've seen cited for the P-38 in a dive are Mach 0.72 without dive flaps and Mach 0.74 with them--this was right on the edge of the envelope, though.
For the P-51, I think the limiting factors were structural integrity (whether your P-51 was one of the occasional ones on which the wings came off), and pilot strength--I gather the Mustang's stick could be very stiff indeed at high speeds.
(Interesting point C.C. Jordan made a while back, about how Robert Johnson was apparently a very strong man and this may have been why he could always outroll everyone in his P-47 at speed.)
Suave1, you should be glad Lockheed didn't get their way. I mean, "Atlanta"? :p
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I was thinking back over about 20 years of these discussions. When it comes to the P-38 vs. P-51 vs. P-47 arguement, it is always the same. For those who haven't been doing this for 20 years, here is the Reader's Digest Condensed Version:
P-51 advocate: Speed in a dive, level speed, critical Mach, range, high speed turn.
P-38 advocate: Climb, range, accleration, low stall speed, medium and low speed turn rate, durability, high and low altitude performance, firepower, gun platform stability, ordinance capacity.
P-47 advocate: Speed, roll rate, firepower, high altitude performance, extreme toughness, ground attack capability, ordinance capacity.
Repeat over and over again until blue in the face. Get testy and annoyed, repeat to infinity.
Many people more learned and qualified than any of us have done this before.
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I have some legitimate questions I'd like some answers to, other than the standard B.S. answers.
There were several things the USAAF and the War Production Board refused to allow Lockheed to use. Nearly every other front line fighter had them.
First, the Hamilton Standard High Activity Hydrostatic paddle prop, first a three and later a four blade version. Obviously it was a huge improvement in performance and reliability.
Second, the K-14 gyroscopically stabilized lead computing gunsite. Again, an obvious improvement.
Third, (and no other plane had it either) was the master combat control, that turned on the gun heater, the gun switches, the light in the gunsite, set the props and the mixture. All you had to do was hit the combat control lever and switch, and throttle up.
Anyone got any legitimate no B.S. answers?
By the way, it was the British that called it the Lightning.
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renegade.... are you talking real life or game situation? :confused:
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Renegade Savage,
Well, too much text to comment all your points, anyway...
The balance point problem of the P-51 (B,D and K) was not really a big issue with correct fuel management.
You certainly know what I meaned when I wrote about leading edge tanks. All combat ready P-38 models before the J-15 had 300 gallon internal fuel capacity (two 90 gallon tanks in the wing center and two 60 gallon tanks in the inner leading edge) and less range than the P-51 without fuselage tank (180 gallon). Later Js had in addition two 55 gallon tanks in outer leading edges which earlier housed intercoolers) and comparable P-51 had in addition 79 gallon tank and still better range even if the fuselage tank was half full.
The P-51 could cruise economically (about 5,5mpg) around 320-350mph true at 20-30k and the P-38 cruised (3,7-4,5mpg) 250-300mph true at these altitudes. The P-51 had a clear advantage. BTW you are the first one to claim that the P-51 could not reach operating altitude before operating area...
Then it should be noted that I have talked all the time about the P-51B with the V-1650-3. And it did over 430mph at 30k, 425mph at 35k and 400mph at 40k. Clearly better than any production P-38.
BTW the V-1710-111/113 was rated at 60" and 3000rpm with the grade 100/130 fuel, I wonder where from your 64" value comes? Also it should be noted that the F30R/L in the P-38L had critical altitude 25800ft without RAM and 28700ft with RAM, the limiting factor was the turbo (overspeeding).
gripen
[ 12-05-2001: Message edited by: gripen ]
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Originally posted by laz:
renegade.... are you talking real life or game situation? :confused:
On which point(s)?
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The later P-38J and L models had 55 or 60 gallon tanks in the leading edges of the wings. At the settings I stated earlier, the P-38 had a greater range than the P-51, with a fuel consumption rate of about 4.9 to 5.2 mpg, with a cruise speed of around 280 to 320 MPH. I'll look up some other fuel consumption data to verify that.
Actually, if you will look again I quoted Captain Arthur Heiden, who flew BOTH the P-38 AND the P-51 in Europe in the 20th FG. He and several others said that if you took off in England and headed directly for the continent, you could not reach mission cruise altitude before landfall in a P-51, but the P-38 would do that with ease. He told me that repeatedly, it is printed in varoious locations, and backed up by another pilot who flew both planes, Captain Stan Richardson Jr., who has also told me the same thing, and been quoted in print, and to my knowledge, no one has ever refuted this, at least not with any proof.
Sure, you can compare the lightly armored and armed P-51B against the P-38, but most people speak of the P-51D. And the P-51B was judged by all to be short of guns and armor. Sure it was slightly faster and lighter. Comparing a fully laden and outfitted plane against a less armed and armored plane with less than a full load of fuel is not an honest and fair comparison.
Those numbers are the Lockheed and Allison numbers for the P-38L. The rating was at 64" of manifold pressure, and the WEP power was 1725 horsepower at 28,700 feet. Military power was 1425 at 54" at 29,000 feet. The turbo speed was oil regulated.
As far as turbochargers go, their speed is controlled by the amount of air taken in by the engine, the RPM, the regulated boost level, and the load. So long as you maintain the same inlet manifold pressure, the same load, and the same engine RPM, turbo speed does not increase. It is easy to figure, X amount of air and fuel is required to achieve Y amount of exhaust pressure at a given load and RPM. Since turbo speed and boost are regulated, so long as you do not put more air and fuel in, and you do not turn more RPM, then no more exhaust pressure is available to spin the turbo faster. I drive and race a turbocharged car, and I've learned turbocharging the hard way.
The way to overspeed the turbo in a P-38 was to either let the oil get too cold and congeal in the regulator, causing it to fail to operate, or to lose dynamic braking on the prop and over rev the engine. Then, the hoses would blow off of the intercooler, the intercooler would explode, or the turbo would overspeed past 24,600 RPM, and explode.
Where is the data that for this P-51B that was able to fly 400 MPH at 40K? No pilot I've ever spoken with or seen quoted said he could get a P-51 B or D over 37,000 feet. For that to be possible, a P-51 would only lose 37 MPH from 26,900 feet to 40,000 feet. No engine with a crank driven supercharger with less than two stages and three speeds could maintain the required horsepower over that wide an altitude range. It simply is not possible, even with every modern advance, for a crank driven supercharger to provide that much boost over that wide an altitude range. What you are saying is that a Merlin engine could maintain in excess of 1700 horsepower from 6,250 feet to 40,000 feet. No other plane equipped with a Merlin of any sort was able to maintain that power level over that altitude range. Even if you figure reduction of drag in thinner air, and figure it far in favor of your argument, and then ignore the fact that there is nowhere near as much lift at that altitude, it is just too far out of line with everything else flying. As a matter of fact, I have not seen any plane driven by a piston engine and a prop that could cover the altitudes you claim with less than a 40 MPH spread in speed. Certainly without a turbocharger. Air density changes at altitudes have far too great an effect on internal combustion engines.
In fact, the Packard Merlin was rated at 1720 horsepower at 67" of manifold pressure, at an altitude of 6,250 feet. At the same pressure, the power drops to 1420 horsepower by only 18,000 feet. That's a drop of 300 horsepower in 12,000 feet. Another 12,000 feet puts us at 30,000 feet. If you lose 300 horsepower in the first 12,000 feet, what do you expect to lose in the next 12,000 feet? And in the next 10,000 feet you'll need to get to 40,000 feet? At the rate it is lost in the first 12,000 feet, you'd lose another 500 horsepower by 40,000 feet. Now, you think a plane with barely 900 horsepower is going to fly 400 MPH? I don't, but I'm just a hillbilly redneck.
I worked on Allison engines for a few years in the seventies and eighties, and was able to talk with guys who worked on both the Allison and the Packard Merlin. The same story came straight from the men who worked on them. Only the turbocharged Allison had good power above 33,000 feet.
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It was stated earlier that the mustang was able to dive to mach .86, I thought I read in americas hundred thousand where they took a mustang and dove it to mach .77 then .78 etc and at mach .81 they decided it was no longer safe to dive the mustang any faster and at mach .81 the mustang sustained considerable airframe damage and had to be written off. mach .75 is listed in the manual for max safe dive speed. mach .675 is listed in the manual for the 38 and states it may be exceeded by 20 mph ias and is considered safe. with dive flaps tony levier stated mach .72 was completely safe with dive flaps and the plane recovers all by itself, these were dives from altitudes above 30,000ft also. mach .745 or .74 w/o flaps was stated to be terminal in warren bodies book for the 38.
it was also stated that the generally acepted 3,500fpm initial rate of climb for the mustang was taken from a mustang that weighed 9,000 lbs, that is about 1,200 - 1,500 lbs lighter than max weight at full internal stores. 3,800 fpm for the lightning is also widely published and this is the lowest rate of climb I have ever seen published for the 38J/L and this rate of climb is for a plane at 17,600lbs take off weight.
when looking at military climb rates for 51D and 38J/L there is about 700-800 fpm difference in favor of the lightning with both planes taking off at similarly loaded weights ie full internal stores minus fuel burned for take off and warm up. two other books credit the 38 with 3,900 fpm @ 5,000 ft so initial would be higher and the other lists 4,000 fpm @ 5,000 ft both books being warren bodies and martin caidens book.
I too have read this in a book on mustangs, I think it was written by Roger Freeman (Classic Publications) and it did in fact state the below.
To quote Captain Arthur Heiden 20th FG 8th USAAF, "You could reach cruise altitude from England before landfall in a P-38, while in the P-51, you still had considerable climbing left to do." I'd prefer to arrive to the fight at altitude and speed, with plenty of internal fuel left to fight and go home.
that book is a good one for listing all the problems that the mustang had. there was a point when the 51 was limited to max dive speed of 450 mph tas due to a few accidents where wings were shed due to landing gear doors and ammunition doors blowing off and causing the entire wing to fail. there seemed to be a lot of structural failures in the mustang when it was flown at very high speeds and very high g loads. there was a 20 lb bob weight added to the control mechanism for the tail surfaces to make the stick heavier to curb over aggressive pilots and lessen structural failures. the book states that the bob weight was not a cure for the problem, but lessened the accidents.
also on the critical mach numbers, isnt there an naca test where a P-51B was used and it stated that critical mach varied with wing skin condition? flat paint, chipped paint, scuffs on natural metal finish, shinny metal finsh and dull metal finish all affected critical mach number? so is the mach .75 and higher figure taken from a plane with highly polished natural metal finish or from one with flat paint?
sorry I got long winded, its a character defect of mine.
[ 12-05-2001: Message edited by: bolillo_loco ]
[ 12-05-2001: Message edited by: bolillo_loco ]
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Wow! Great thread. Alot of good data here. Hoever, being as anal retentive as I am, I have to clarify something. Critical Mach is not the Mach number at which flight controls be come in-effective (Although that generally happens as a result of exceeeding the critical mach number on World War II aircraft). Critical Mach number is the Mach number at which shock waves begin to form on the aircraft (i.e.-it is the beginning of the transonic regime for that particular aircrafts' flight envelope). As such, it will lead to all kinds of negative effects on World War Two aircraft. Some of this is due to flow separation (which can also induce vibrations if it separates and re-attaches or impinges on surfaces downstream) and if the plane forms shock waves fast (i.e., usually large curvature on the upper surface of the wing as on the P-38) this will cause the shock waves to form rapidly on the wing and when you get shockwaves on the wing then the A.C. (Aerodynamic Center) will shift rearward from approximately 25% MAC to 50% MAC in which case the horizontal tail is now to small to lift the nose, etc. Hey, Zig, do you have the tail volume calculations handy? It's been awhile since I have seen those. Might be a bit illuminating here. Anyway, just wanted to be clear on what critical Mach number is.
Based on everything you guys posted here, do you any of you have info on loiter times? In my book on the JV-44, Galland said that during the last year of the war, they really hated the P-38 the most because of it's ability to spend so much time loitering over the German airfields and keeping them capped. So I was just curious as to how the time on station of the P-38 compares to that of the P-51 series. You guys have any info on that? Thanks.
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Renegade Savage,
I checked all sources here at home and I could not find noone claiming that climb speed during on way to Germany was a problem (including Mr. Heiden). The P-51 cruised and climbed at faster speed (lower climb angle) than the P-38. It is pretty natural that it covers longer distance while climbing to the given altitude. Same way I can argue that the P-51 reached continent faster than the P-38.
The P-51B (and the C) with fuselage tank was the major model in the ETO. The data I have is from a USAF document (Tactical Employment Trials North American P-51B-1, Army Air Forces Board Report, 12th February 1944). I have compared performance of the P-51B-1 to the P-38J-1 when loaded for at least similar range and with engine ratings which are authorized by the USAF. Also my numbers for the V-1650-3 powered P-51B are supported by the tests by the RAF and RR. The V-1650-3 was an excellent high altitude engine and also reliable, same can't be said about some other engines.
The V-1710-F30R/L was rated by Allison, USAF and Lockheed for WEP 1600hp, 60"@3000rpm with the grade 100/130 fuel (AN-F-28). In addition manufacturer rated the F30R/L for the WEP 1725, 60"@3200rpm with grade 150 fuel, this rating was never authorized by the USAF for service use. Also it should be noted that the standard USAF late war fuel was grade 100/130, there might have been very limited quantities of other fuels (grade 150, grade 140, grade 115/145) available for special purposes. Actually this has been discused here before and so far noone has come up with the clear evidence that those higher ratings had been used in the large scale service (and how about blade tip speeds at 3200rpm?). BTW how critical altitude for the rating you claim is the same as for the 60"@3000rpm with RAM (should be lower?).
About overspeeding supercharger you are wrong, air density decreases when altitude increases so speed of the turbo increase when altitude raises. (thanks HoHun, I did not even note that error, we are generating far too much tetxt...)
bolillo_loco,
I'm refering Wright field tests on P-51D by Major F. Borsodi. He reached mach 0,86 (instrumented) in the dive from 40k and actually he even took pictures of the shock wave in his tests. The critical mach number is the speed where compressebility effects start as Sundog noted.
gripen
[ 12-06-2001: Message edited by: gripen ]
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Sundog,
The P-38's endurance was superb. Missions in excess of 2,000 miles resulted in ten or more hours in the cockpit, placing considerable demands on the pilot. This required 300-gallon drop tanks, which were not available in the ETO; with the smaller 165-gallon tanks, the P-38's endurance would be roughly equal to the P-51's at seven hours or so.
Anyway, are you sure Galland said the P-38? By 1945 the Lightning had been phased out of 8th AF, and was on its way out of 9th AF as well due to shortages of replacements and spares (most likely diverted to the Med and Pacific). Only one group, the 474th FG, retained their P-38s until the end of hostilities after petitioning to keep them.
Moreover, Galland was never very complimentary of the Lightning, calling it a "mistake" and repeatedly comparing it with the Bf 110. While I think the bulk of evidence is against his viewpoint (particularly from the other theatres), he never seems to have wavered from his views.
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Hi again, Hilts!
>The P-51 was easier to fly in that respect. But there was no great disparity in cruise speeds, and if you had to fly with the bombers, then the bombers were the limit anyway.
Fighter operations were complex enough that much of the time, fighters were not tied to the bombers as cover was typically divided into outbound cover, target cover and return cover missions. Much of the time, fighters were cruising on their own, and when they were with the bombers, they'd cruise at high speed too to be prepared for action, zigzagging to stay with the bombers.
>Also loaded out for the same mission, the P-38 could climb out towards enemy territory directly, where as the P-51 required you either reach enemy territory with lower altitude, or burn fuel circling while you climbed.
Since fighter missions were scheduled as described above, this was no problem operationally.
>These compare true air speeds at WEP, 67" of manifold pressure for the P-51, and 64" for the P-38.
Do you mean to suggest that 64" manifold pressure was an operational standard for the P-38?
>Below 20,000 feet, and above 30,000 feet the P-38 was a better ride.
Here's a quote from a recent interview with P-38 ace Gerald Brown on Dogfighter.com:
"DF: So how did the P-38 match up against the Luftwaffe? [Interviewer’s note: Gerald Brown flew the P-38J and H models in ETO combat.]
GB: I would say that under 25,000 it matched up well, but around 25,000 - if they had the advantage - they could pick us off. You see, at high altitude the P-38 had a liability problem as it would compress in a dive.
[...]
DF: What was a better fighter plane? The P-38 or the P-51?
GB: I liked both! But the P-51 was a better aircraft against the Germans. Early on the German, like a street bully, could pick a fight and then break it off against the P-38. He couldn’t do that with a P-51. With comparable pilots, the P-51 will come out on top."
>There were several things the USAAF and the War Production Board refused to allow Lockheed to use. Nearly every other front line fighter had them.
This is probably not the answer you're looking for, but the truth may well be that nearly every other front line fighter was considered superior to the P-38. (That's not my personal opinion, but the USAAF leadership's!) Here's a telling remark from General Doolittle: "The P-38 was a second-rate fighter when compared to the P-47 and P-51". (General Spaatz seems to have shared his opinion.)
Since they considered the P-38's problems unsurmountable, I'd speculate that the low critical Mach number of the airframe - which couldn't be increased without designing an entirely new aircraft - was the basis for their opinion. A low critical Mach number meant the P-38 was hamstrung at high speeds as well as at high altitude. Speed and altitude, however, were the cornerstones of WW2 fighter tactics.
>So long as you maintain the same inlet manifold pressure, the same load, and the same engine RPM, turbo speed does not increase.
As static air pressure decreases with increasing altitude, the pressure differential over the turbocharger increases too, introducing the risk of turbocharger overspeeding. Not a factor in auto racing, I admit :-)
Regards,
Henning (HoHun)
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This is probably not the answer you're looking for, but the truth may well be that nearly every other front line fighter was considered superior to the P-38. (That's not my personal opinion, but the USAAF leadership's!)
Yes. In a very specific context--the high-altitude escort role, in the European Theatre. This is the context in which the P-38 performed by far the most poorly out of all the environments it fought in. While the 8th AF ETO record is certainly important, I think it would be a mistake to draw a complete conclusion based on European escort experience alone.
General Kenney of the 5th Air Force (Pacific Theatre) went out of his way to get P-38s for his fighter groups, preferring them to P-51s. 5th AF's premier air-to-air squadrons continued to fly P-38s until the end of the war.
As previously mentioned, the 9th AF's 474th FG petitioned explicitly to retain their Lightnings rather than re-equip (obviously, with either P-47s or P-51s--probably the former).
Also note how Gerald Brown makes a clear distinction between the P-38's relative abilities above and below 25,000 ft. I've seen that far too often for it to be a coincidence.
"Corky" Smith, 12-kill P-38 ace with the 80th FS "Headhunters":
"I flew the P-51 after the war over a two year period. A good ship--but could only better the P-38 at altitudes over 20,000 feet. It was well suited for the European theater where high altitude combat was predominant..."
Stan Richardson Jr (who, like Gerald Brown, flew with the 55th FG), as quoted by C.C. Jordan:
"My closing comment in this note to you is relative to the capabilities of the P-38 vs the P-51 in simulated combat. Below 25,000' I'd have 'waxed' a '51 every time. One advantage the P-51 had was a wonderful gunsight (the K-14). The gunsights in the '38 were very basic. Kentucky windage helped a lot!"
[ 12-06-2001: Message edited by: Guppy ]
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Here are ratings for the V-1650-3 from the P-51D manual (some P-51Ds had the V-1650-3 instead the V-1650-7).
WER 67"@3000rpm lo 1595hp 11700ft no RAM, 17000ft with RAM
WER 67"@3000rpm hi 1295hp 23200ft no RAM, 28800ft with RAM
MIL 61"@3000rpm lo 1450hp 13700ft no RAM, 19800ft with RAM
MIL 61"@3000rpm hi 1190hp 25600ft no RAM, 31200ft with RAM
CON 46"@2700rpm lo 1120hp 17500ft no RAM, 20500ft with RAM
CON 46"@2700rpm hi 940hp 29500ft no RAM, 34400ft with RAM
Also manufacturer claims that the Merlin 61 (RR equivalent for the V-1650-3) could maintain sealevel atmospheric pressure MAP (about 30") to an altitude of more than 40k.
gripen
[ 12-06-2001: Message edited by: gripen ]
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Yes, Galland was critical of EARLY P-38's. Galland's opinion was formed when the P-38 had no dive flaps and the majority of pilots in the 8th AF were relatively green. A green pilot in a plane as hard to fly as the P-38 was probably was an easy target. And if the P-38 pilot did gain the advantage, the German could dive and run. Consider that when Galland met John Lowell (a pilot of equal skill) in a later P-38, Galland said Lowell damn near killed him, and Lowell only broke off to go home for fuel. Hearing Lowell describe the fight, Galland said "You son of a squeak, you Golly-geened near killed me that day!" Several pilots of comparable skill in P-38's shot down noted German aces. So, the 8th AF still considered the P-38 to be second rate, even when the P-38 with a pilot of good skill could and often did shoot down the very best Germany had to offer.
Once again, regarding turbochargers, only the exhaust OUTLET and the intake INLET are exposed to atmoshperic pressure. Pressure on the exhaust (turbine) side is exerted by engine exhaust. This is what drives the turbocharger. The intake side (impeller, or compressor) pressurizes the intake system. Whatever manifold pressure exists, is the resistance to the force exerted to spin the turbocharger by the exhaust pressure. The amount of exhaust pressure available to drive the turbocharger on an engine operating at a given RPM and intake manifold pressure is the same regardless of the altitude. If the intake manifold pressure and RPM do not change, then turbocharger speed will not change. If you could increase RPM, or lower the intake mandifold pressure, or increase the pressure on the INLET side of the impeller housing, then you could increase turbo speed.
In the case of the GE turbocharger on the Allison V1710 on the P-38, neither housing is variable, nor is the nozzle. The speed is regulated by an oil pressure regulator. So long as oil pressure and temperature remain within normal operating parameters, the regulator is capable of bypassing enough exhaust pressure to properly limit the RPM of the turbocharger. Load on the engine is controlled by prop pitch, and therefore, at maximum throttle, with autopitch, engine RPM and load are constant. The intake side of the turbocharger is exposed to manifold pressure, in this case you state 64". That is the load seen by the turbocharger exhaust turbine. At a constant load, constant manifold pressure, and constant RPM, a constant amount of exhaust gas pressure will be generated by the engine. This constant pressure will be applied to drive the turbine side of the turbocharger, which is directly coupled to the impeller or compressor side, which is still seeing a constant intake manifold pressure of 64". No load change exists, no force change exists, so no speed change occurs. Even if you remove the load from the engine, RPM will increase but exhaust pressure will decrease. Eventually, you can increase RPM enough to overspeed the turbocharger, if the engine will turn enough RPM. If the atmospheric pressure were to drop so low that the there was not enough air available to create 64" of manifold pressure, then the load on the impeller would decrease, and the turbo would overspeed. So yes, it is possible to overspeed the turbo at high altitudes, but I find no mention of this with the P-38 or the P-47, though both did use the same turbocharger. The only evidence of turbocharger overspeed comes together with a failure of another system or part of the system. The Curtiss prop could lose its dynamic brake and over rev the engine, eventually over reving the turbo. The oil cold be allowed to get so cold it congealed in the turbocharger regulator, renderring the regulator inoperative, eventually over boosting and possibly over reving the turbocharger.
The only factual evidence against the P-38 at high altitudes was the dive problem. With the dive flaps, the P-38 could and did fight at high altitudes, and was far less likely to spin out of a fight at high altitudes and was far easier to recover.
The P-47 used the same turbocharger at the same range of altitudes. Further, the P-47 was tested in an overboost condition that exceeded all operating parameters of the engine and the turbocharger without a failure of either.
That is why a turbocharger makes a better altitude compensating device than a crank driven supercharger.
While the low critical Mach number was part of the equation, the fault the 8th AF found with the P-38 is that the early planes lacked automatic control of oil and coolant temperatures, and attempts to operate the engines at full power when they were too cold resulted in engine failures of one form or another. The early versions intercoolers were not efficient enough, and seperated the lead from the fuel, lowering the octane numbers. The requirement of Lockheed by the USAAF to use the Curtiss electric prop caused electrical and engine failures, compouned by poor maintenance training for the care of the electric props. Failure of the pilot to set the radiator doors resulted in overheating at full throttle.
However, the J and later models changed all that. The dive flaps allowed the P-38 to chase in a dive, even though the 8th refused to change their instructions and policy. The automatic controls for the oil coolers, and radiators eliminated the cooling problems, and the turbocharger overspeed due to oil congealing in the regulator. The new core type intercoolers allowed the P-38 to use the full power of the Allison. The fact that the 8th AF refused to acknowledge and take full advantage of these changes is not an indictment of the plane, but a further indictment of Doolittle and Spatz, who were chastized or removed for failure to be agressive enough. The fact that the 5th, 9th, and 15th AF's were willing and able to take full advantage of them should be considered.
The dive problems of the P-38, as noted by Gerald Brown, are well known, and acknowledged by bothe sides of the arguement. On the other hand, they are much less of a problem for the J and L models, by far the most numerous of the P-38 line. Further, several pilots were known to have figured out how to dive in a P-38 even without the dive flaps.
One of the most critical errors of the 8th AF is their complete and dismal failure to acknowledge and make use of the experienced pilots who came from North Africa. The fact that the 8th AF completely failed to utilize the skills and experience of those pilots is another prime example of incompetence in the command staff of the 8th AF, and taints their opinion. Most pilots who came to the 8th from North Africa were very successful, and what they knew would have been invaluable to the new pilots, but the 8th AF chose to completely ignore this. The 8th was never known for the use of good tactics, just the use of massively overwhelming numbers. One need only witness their insanely stupid attempts to practice mass daylight precision bombing without fighter escort.
The mere fact that the USAAF and especially the 8th AF hog tied the P-38 by denying Lockheed the use of the K-14 gunsite, the Hamilton Standard prop, and the Lockheed master combat control, and then complained bitterly about the performance of the P-38 is enough to tell even the casual observer there was something very wrong with the USAAF and the 8th in particular. The fact that the P-38 accounted for more Japanese planes than most other fighters combined should be enough to raise a few warning flags. As should the success of the P-38 over North Africa, Italy, and the Med., all with a different leadership than the 8th.
When every other group is able to get completely superior performance and results from an aircraft, and most facing the same planes and some of the same pilots as the 8th, but the 8th can barely keep it in the air, and is critcized for heavy losses and poor leadership and tactics overall and in general, you have to look closely at the command staff of the 8th AF before you lay the blame solely on the P-38.
One more little fact. The 5th AF had a guy named Major Thomas B. McGuire, a successful guy, with 38 victories. Now, Genreal Kenney and Colonel McDonald had Major McGuire write a manual to indoctrinate new pilots to the 5th AF and the Pacific theater of operations. It included the flight characteristics of every Japanese plane, the tactics of the pilots, and all the information necessary to allow the new pilot to enter combat with confidence and leave combat with success. Funny, the 8th AF had several successful P-38 pilots, but none were ever asked to write a manual to help the new pilots learn to fly their plane in combat, and give them the tactics and knowledge needed to win. The successful P-38 pilots of the 8th knew how to beat the Germans, and had moves to conquer the dive problems, and tactics that worked at high altitudes. But the knowledge was never passed on to all of the new pilots who were assigned the P-38. One more reason poor leadership in the command staff of the 8th AF was the primary and major reason for the less than stellar record of the P-38 in Europe with the 8th AF.
Like the guy said, we are generating way too much text here. Time to move on.
[ 12-06-2001: Message edited by: Renegade Savage ]
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I can't delete this entirely, just edit it to nothing.
[ 12-06-2001: Message edited by: Renegade Savage ]
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FYI: The quote I was referencing by Galland was in the Classic Publications book on JV-44. They really didn't get into Gallands thoughts on the P-38 with respect to A2A combat. He was just making a statement about the USAAF's ability to loiter over Luftwaffe airfields for hours and cap them and he said the P-38s were usually the ones he disliked the most because they tended to CAP the luftwaffe bases the longest.
My 'guess' would be that P-38s were also used for this, because P-51s were escorting bombers and P-47s were being used for A2G. But that's just speculation on my part.
For reference:
Classic Publications Web Site (http://www.classic-books.co.uk)
BTW, I highly recommend anything by these publishers. Their Me-262 series is far and away the best publication I have seen on thataircraft. Their Hs-129 book was excellent as well. Their Colour series are excellent. I recently received the second volume of their American Eagles Series on the P-38 in the ETO, which I highly recommend to all the P-38 fans here :)
[ 12-06-2001: Message edited by: Sundog ]
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one of multiple posts deleted.
[ 12-06-2001: Message edited by: Renegade Savage ]
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38 fanactics...here is a MUST have book. http://home.att.net/~Historyzone/Widewing.html (http://home.att.net/~Historyzone/Widewing.html)
xBAT
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:) I wish xbat. I bought the last copy of the P-47 book that Warren Bodie said he had. Autographed too. But the P-38 book has been out of print for years now and if you can find it you'll usually pay a steep price for it :(
edited: I just clicked the link and saw it's a new re-released edition in softback! Oh Santa!!!!!!!!!!!!!!!! :) Thanks xbat for the heads up!
Westy
[ 12-06-2001: Message edited by: O'Westy ]
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Hi Hilts,
>Consider that when Galland met John Lowell (a pilot of equal skill) in a later P-38, Galland said Lowell damn near killed him, and Lowell only broke off to go home for fuel.
Let me point out that I don't believe the Lowell story, at least as posted on several boards a year ago. A mid-1944, post-invasion date with Galland personally flying a Reichsverteidigung mission in a Fw 190D-9 before the type went into production, over a 500 ft deep open-cast mining pit in the North German plains is not excactly credible. (I guess it's probably based on a real event, but somehow got distorted or embellished with contradicting details.)
>If the atmospheric pressure were to drop so low that the there was not enough air available to create 64" of manifold pressure, then the load on the impeller would decrease, and the turbo would overspeed. So yes, it is possible to overspeed the turbo at high altitudes, but I find no mention of this with the P-38 or the P-47, though both did use the same turbocharger.
Glad we agree!
Overspeeding certainly was a possibility as the P-47 examined by the German test pilot Hans-Werner Lerche was fitted with an overspeed warning light. He was surprised to see that the aircraft relied on pilot inputs to prevent engine damage, which was a problem for the German sense of technical perfection. He admitted that the German mentality could prevent cutting-edge technology from becoming operational, though.
Oh, by the way, did you mean to suggest that 64" manifold pressure was an operational standard for the P-38? I almost forgot about this point.
>The dive flaps allowed the P-38 to chase in a dive
Even with the compressibility flaps, as Kelly Johnson called them, the critical Mach number of the P-38 was far below that of the P-47, the P-51, the Spitfire, the Me 109, the Fw 190, and most other contemporary fighters. Kelly Johnson himself made a list of the shortcomings of his design, and low critical Mach number even with the compressibility flaps was one of his points.
>The fact that the P-38 accounted for more Japanese planes than most other fighters combined should be enough to raise a few warning flags. As should the success of the P-38 over North Africa, Italy, and the Med., all with a different leadership than the 8th.
The mission of the 8th Air Force necessarily required high-altitude combat. In other theaters, and for the tactical mission of the 9th Air Force, high-altitude capability wasn't crucial. (Nevertheless, they had converted two of their three P-38 groups to other types before VE day.)
In general, that the P-38 was released for use in other roles and theatres where it could be successful seems like a very good decision to me.
>Now, Genreal Kenney and Colonel McDonald had Major McGuire write a manual to indoctrinate new pilots to the 5th AF and the Pacific theater of operations.
You're right that information sharing could be a big problem between the different US forces.
If you're talking about McGuire's "Combat Tactics in the SouthWest Pacific Area", however, it was only published May 1944, when the P-51 already outnumbered the P-38 7 to 4 groups in the 8th Air Force. Most of his advice is quite specific to the Pacific theatre anyway, and the rest is so general (like the description of the four-finger formation) that I don't think the 8th Air Force needed McGuire's write-up to teach it to their pilots.
>Like the guy said, we are generating way too much text here.
It might improve the situation if you'd erase two copies of your triple post.
Regards,
Henning (HoHun)
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Hi Guppy,
Thanks for the quotes! That's good information :-)
>>This is probably not the answer you're looking for, but the truth may well be that nearly every other front line fighter was considered superior to the P-38. (That's not my personal opinion, but the USAAF leadership's!)
>Yes. In a very specific context--the high-altitude escort role, in the European Theatre.
Exactly! That's why I wouldn't totally agree with the 8th Air Force assessment - the P-38 has some strengths that make it an excellent aircraft in other roles. Especially in an online game's arena, where high-altitude performance means little, it's quite a competent fighter!
Regards,
Henning (HoHun)
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Hm... to be honest, I don't know what is going on here, I see several posts by Renegade Savage, some are old some are new...
Anyway, overspeeding turbo was possible, see the P-38 manual: "Above 25000 feet, turbo-supercharger overspeed is possible". And with a bit of technical knowledge it's easy to figure out that when air density decreases turbo needs to turn faster to keep given MAP. Also it is easy to figure out that overspeeding at (questionable) 64" MAP happens at lower altitude than at 60" MAP.
About comressebility it should be noted that it was not just a dive problem because the critical mach number decreased under increasing g load, see compressebility table on the manual or explanation in the America's Hundred thousand. So compressebility was not just a dive problem but it also greatly reduced maneuverability at high altitude. BTW all this is discused above.
gripen
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The answer to my question was exactly the same tired B.S. I've come to expect.
First, everyone quotes data taken from the already light P-51B, with less than a full mission load, approximately 1400 pounds light, and running on 150 performance number gas not often used in actual combat. Then they insist on comparing it to a fully laden P-38L (the heaviest of all P-38's), run on 130 performance number gas. Total B.S. comparison. Same story as always.
What I said about 64" of manifold pressure and 1725 horsepower was that those were Lockheed and Allison numbers. The fact that the USAAF did not accept them is just another case of the USAAF screwing up.
Then we have the 8th AF as the only group to complain about the P-38. Now all along the USAAF insists on equipping the P-38 with substandard props, holding up production of better versions, refusing performance enhancements at every turn, and then complaining about the result.
Now, there is the issue of training and the 8th AF mission profile. Both the 20th AND the 55th FG's came to Britain with no experience in operation at over 27,000 feet. Why is it this happened when the 8th AF already knew for several months they were going to require these missions that the P-38 pilots and planes were never even trained or tested at all at altitudes above 27,000 feet.
The 20th and 55th FG's entered service and went 100% operational in less than 30 days, with few experienced combat pilots and even fewer experienced leaders. Compare this to the P-51 groups of the same period which were comprised of or led by former RAF Eagle pilots who had long term combat experience in Merlin equipped Spitfires and Mustangs. Compare that to the P-47 groups that had over 700 planes and pilots and months of experience. Comparing pilot with no combat experience, and no high altitude training, in a plane never adequately tested by the USAAF at high altitudes, to an experinced group of combat veterans is absurd.
I never meant that McGuire's booklet would have been useful to the 8th AF. What I meant, and you obviously completely missed, is that the 8th had experienced combat pilots, indeed, experienced P-38 combat pilots, who were quite successful, and yet completely failed to use the knowledge and experience to indoctrinate new P-38 pilots.
I really do not give a damn whether you believe the Lowell vs. Galland story or not, that is your choice. It was told by a respected veteran pilot with no reason to lie, published, and never disputed by either pilot. Considering you are not a noted historian, a respected and published author, nor a veteran pilot who was there when it was told or when it happened, your opinion of the authenticity of the story is worthless to anyone but you. You have never been able to prove to anyone's satisfaction but your own that it did not happen.
Once again, this turns into the same tired load of crap. I deleted the duplicate posts. Still a waste of time, and it takes 3 minutes to load this thread on dial up.
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Renegade Savage,
I wonder how many times I should note that in the USAF test the P-51B-1 had full internal load (180 gallons of fuel+ammo+what ever) and the test was with standard fuel and authorized MAP 67". The P-38J-1 in the comparison was also with full internal load (300 gallons of fuel+ammo+what ever) and 60". So what's wrong in this comparison?
gripen
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Nah Nah Westy :p
I got an original hardcopy of that book, which believe it or not, I found on a dusty half hidden shelf at a Waldens book store in some mall somewhere in Atlanta a couple of years agoif I remember right. Was there for a business trip, found it and screamed "COME to MOMMA!!"
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Exactly! That's why I wouldn't totally agree with the 8th Air Force assessment - the P-38 has some strengths that make it an excellent aircraft in other roles. Especially in an online game's arena, where high-altitude performance means little, it's quite a competent fighter!
We seem to share a lot of views in common. :)
I'd say that the P-38J-25/L, with aileron boost, dive flaps and nearly all the bugs worked out, was a good high-altitude fighter. However, the P-51 (especially the B with critical altitude up near 30k) was a very good high-altitude fighter, and by most accounts the P-47 pretty much ruled the sky above 25,000 ft.
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The P-38 design looked good in 1940-41 when the USAAC was scrambling to find a fighter that could match European designs. At that time it was believed that if you wanted long range you needed two engines, so the P-38 started to look good to Army planners who knew war was coming. They knew the P-40 and P-39 wouldn't cut the mustard.
By 1944 there were single-engine planes that could do the same job as a P-38, so an expensive, hard to maintain twin was no longer warranted by the situation. If the war had dragged on one more year the P-38 would probably have been phased out by the P-51H and P-47N, at least until jets became combat ready.
It doesn't matter how the P-38L performed compared to the P-51D. Whatever the differences were between the two, a second engine was not justified anymore.
ra
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Hi Hilts,
>What I said about 64" of manifold pressure and 1725 horsepower was that those were Lockheed and Allison numbers. The fact that the USAAF did not accept them is just another case of the USAAF screwing up.
Well, let's assume the USAAF screwed up - do you have any documents supporting the 64" Hg number? Even if not operationally used, I think it would help your cause by emphasizing the unexploited development potential of the P-38.
>Now, there is the issue of training and the 8th AF mission profile.
I'm convinced the 8th Air Force dropped the P-38 because of its low critical Mach number. If the P-51 would have displayed teething troubles similar to the P-38, they probably would have stuck to it anyway - just think of the gun jam problem plaguing the P-51. No amount of training can make you exceed the critical Mach number.
>What I meant, and you obviously completely missed, is that the 8th had experienced combat pilots, indeed, experienced P-38 combat pilots, who were quite successful, and yet completely failed to use the knowledge and experience to indoctrinate new P-38 pilots.
I admit I missed that.
However, there were fresh P-51 groups with no experience either who weren't considered as problematic as the P-38 groups. If you'd be in command of the 8th Air Force, would you rather equip your groups with a fighter that requires expert mechanics and ace pilots to be successful, or with another fighter that does just as well with average ground and air crews while requiring just half the engines, spare parts, and fuel? This is a rethorical question of course, but if you'd try to see it with the eyes of the 8th Air Force staff, you might understand why they didn't decide in favour of the P-38.
>The successful P-38 pilots of the 8th knew how to beat the Germans, and had moves to conquer the dive problems, and tactics that worked at high altitudes.
Could you go into more detail here? This sounds quite interesting.
>I really do not give a damn whether you believe the Lowell vs. Galland story or not, that is your choice. It was told by a respected veteran pilot with no reason to lie, published, and never disputed by either pilot.
I felt obliged to point out three major contradictions in the Lowell story for the benefit of readers unfamiliar with the story.
The three contradictions are:
- There was no open-cast mining near Hannover.
- Galland was completely tied up in organizing a Luftwaffe response after the Allied invasion and is highly unlikely to have flown operational missions with the Luftwaffe. If he did, he'd have mentioned it in his memoirs "Die Ersten und die Letzten", which he didn't.
- The Fw 190D-9 didn't enter production any earlier than late September 1944 and was not available in squadron strength at the date of the incident.
As long as these apparent contradictions aren't resolved, I'll consider the authenticity of the story doubtful. I'm entirely comfortable with you ignoring these contradictions, but I'm sure some of the readers of this thread are a bit more sceptical than you.
>Once again, this turns into the same tired load of crap.
To be honest, I think it's "the same" because you always leave the scene when facing serious opposition, just to start it over again at some later time.
How about showing a bit more patience now? We might actually learn something new! :-)
Regards,
Henning (HoHun)
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If the war had dragged on one more year the P-38 would probably have been phased out by the P-51H and P-47N, at least until jets became combat ready.
If that was so, why was a second P-38 manufacturing facility (Consolidated-Vultee) beginning production just as the war ended?
The twin-engine factor was specifically cited by Fifth Air Force as a reason why the P-38 was preferred to the P-51. The second engine wasn't "necessary", but on long-range missions with little prospect of rescue the pilot's morale was a lot better when he didn't have to sweat every time the engine coughed.
The longest fighter missions of the war (10+ hours, 2,000+ miles) were flown by Lightnings, just weeks before the Japanese surrender. I think that says something.
[ 12-06-2001: Message edited by: Guppy ]
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quote "Well, let's assume the USAAF screwed up - do you have any documents supporting the 64" Hg number? Even if not operationally used, I think it would help your cause by emphasizing the unexploited development potential of the P-38."
I do not know about the 64" MAP, but the 1,725 hp figure and 440 mph tas for the P-38L is stated in warren bodies book "the lockheed P-38 lighting on more than one occasion. he states that the second LO series of 38L production batch used this power as standard. not the first 38L series which used the same power limitations as the J series. he states in his book that the second batch had new turbo charger regulators that were improved. That is what warren bodie states anyway.
Tony levier states that mach .72 was completely safe with dive flaps for the P-38 and many manuals and pilots stated that recovery was effortless with dive recovery flaps. also dives from 20,000 ft are said to have been no problem for the 38 with or with out flaps. the P-51 series is stated to have a max safe dive speed of mach .75, is there that much of a difference? the P-38's pilots manual states as we all know mach .675 w/o flaps and it may be exceeded by 20 mph ias. how much is 20 mph ias at altitude? it could be a decent gain not?
climb rates, the three tests that I have seen for the P-51B gave data that stated
443 mph tas rear fuselage tank was removed
440 mph tas rear tank empty at take off
430 mph tas rear tank full at take off
initial climb rates for the mustang that are in the mid 3,500 fpm range are taken from mustangs that either had the rear tank removed or empty at take off. 3,000 fpm sticks in my mind for a mustang with rear tank full of fuel.
somebody stated that the P-38 was a J-5-LO and did not have the leading edge tank in place for the climb comparison. this would make the take off weight at 16,800 yet the test lists the a/c weight at 17,600. this is a 38 with the leading edge tanks in place and full at take off. The P-38H had a military power initial rate of climb at 3,500 fpm. The only difference for a climb comparison between a 38H and a 38J/L is the H is lighter than the J and the H series can only make 1,600 hp 60" MAP up to 10,000 ft.
also 3,800 fpm is the slowest rate of climb listed in the 3 books that I have for the P-38 while using WEP power.
3,800 fpm initial in americas hundred thousand
from martin caiden's book
3,900 fpm @ 5000 ft
3,600 fpm @ 15,000 ft
3,100 fpm @ 25,000 ft
warren bodies book says
4,000 fpm @ 5,000 ft and 23,000 ft was reached in 6.2 minutes.
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<<<If that was so, why was a second P-38 manufacturing facility (Consolidated-Vultee) beginning production just as the war ended?>>>
I don't know, but I'm sure it isn't because anyone wanted to increase the number of P-38 units operating. The decision to build that plant was probably made a year earlier. War situations can change much faster than plans can, so often existing aircraft were ordered in anticipation of future needs. Even the Wildcat was being manufactured until May '45.
<<<The twin-engine factor was specifically cited by Fifth Air Force as a reason why the P-38 was preferred to the P-51. The second engine wasn't "necessary", but on long-range missions with little prospect of rescue the pilot's morale was a lot better when he didn't have to sweat every time the engine coughed.>>>
Pilot's morale was not a factor in selecting aircraft, effectiveness was. By late in the war it was clear that two engines did not increase effectiveness or survivabilty over single engine types. The overwhelming majority of P-51 and P-47 combat sorties ended with a safe landing back home.
Over Fortress Germany a second engine did not guarantee the pilot would make it home. War planners take those kind of things into consideration, as they did maintenance loads.
As the P-38's performance no longer exceeded that of single engine types, it found a niche flying long range missions over the Pacific, were the ocean was more of a threat to the pilot's chances of survival than Japanese planes were.
<<<The longest fighter missions of the war (10+ hours, 2,000+ miles) were flown by Lightnings, just weeks before the Japanese surrender. I think that says something.>>>
B-29s were escorted to Japan mostly by P-51's, with P-47N's slated to begin escort duties at war's end. That says something too.
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I don't know, but I'm sure it isn't because anyone wanted to increase the number of P-38 units operating. The decision to build that plant was probably made a year earlier. War situations can change much faster than plans can, so often existing aircraft were ordered in anticipation of future needs. Even the Wildcat was being manufactured until May '45.
That may well be true too, but a year earlier the Lightning had just been phased out of Eighth Air Force. Hardly what I'd call a spur for increased production.
I gather the reason the Wildcat was still in production in '45 was that it occupied much less volume than either the Hellcat or Corsair, and so was used to equip the smaller escort carriers.
Pilot's morale was not a factor in selecting aircraft, effectiveness was.
Pilot morale is directly related to effectiveness. Fifth Air Force realised this.
Over Fortress Germany a second engine did not guarantee the pilot would make it home. War planners take those kind of things into consideration, as they did maintenance loads.
As the P-38's performance no longer exceeded that of single engine types, it found a niche flying long range missions over the Pacific, were the ocean was more of a threat to the pilot's chances of survival than Japanese planes were.
I agree with your main points here. I simply wished to illustrate that there were circumstances in which the second engine was extremely useful. Over Germany, it was only a marginal improvement, if at all. On a long-range over-water mission with no SAR available, it was very important.
The P-38 did have another advantage in the Pacific, in that it could operate out of forward fields which neither the P-51 nor P-47 could handle.
B-29s were escorted to Japan mostly by P-51's, with P-47N's slated to begin escort duties at war's end. That says something too.
Yes, it does. The P-51 and P-47N were very fine long-range aircraft. However, a pilot who had to bail out or ditch in the water between Iwo Jima and Tokyo had at least some prospect of being picked up by friendly naval or flying-boat units. (Still a lot more dangerous than bailing out over France, though.)
I agree with most of your conclusions, ra. I don't think the number of P-38 units was set to increase by the end of the war, and I'm not disagreeing with the increasing use of the P-51 and P-47N. I'm simply saying that the production orders cancelled at war's end would have kept the Lightning rolling off the line for most of a year, and the evidence strongly suggests that at least one of the major Pacific US air forces would keep using them.
[ 12-06-2001: Message edited by: Guppy ]
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I'm not really out of patience with the discussion. But one thing I take exception to is people who persist in questioning the honor and honesty of decorated combat veteran pilots. Now, I'm going to post the story we are talking about below, including the names of all involved. Now, you tell me why there is any reason to believe that Lowell, Galland, Gabreski, or Foss are either lying, or too stupid to have the foggiest idea what they are talking about. Once again, this story was told in front of a hundred witnesses, and was published in a well known and respected book.
"Came across it by accident in a book called Top Guns, by Joe Foss and Matthew
Brennan, that is sitting on my shelf."
This is John Lowell's account of his fight with Galland 38 vs 190D9. Scan at the
end is Lowell getting the DFC
"One of our last P38 missions was a flight to protect bombers on a mission near
Berlin. My squadron was flying top cover. We were attacked from above, out of
the sun by sixteen long nosed FW 190s. I was alerted by a flight leader in our
squadron. I saw a flight of four Focke-Wulfs coming in from too high to
effectively fire on my flight so I quickly slowed the flight as we opened up
laterally for a defensive break and a head on attack that the Germans never
wanted when they were fighting P38s. The lead German flight passed very close
over me with throttles back trying to slow down.
I looked up at the German plane. The pilot was looking down at me as he eased
ahead and close above me into sure death, unless he could take violent evasive
action. He split-Sed and I followed him. He nearly got out of my sight because
the P38 high-speed compressibility problem kept me from staying with him in a
vertical dive. I stayed out of trouble by doing a vertical barrel roll to pull
several Gs and keep my speed under control. Finally he turned to find me, and I
cut across to close with him. Then the fight started.
He was a fantastic, wild, talented pilot who pulled all the tricks I had ever
seen. But finally I got into a tight Lufbery with him and used my clover-leaf
surprise to get a few strikes. None of them harmed the power unit. The
long-nosed 190 had methyl injection that was usable for ten-second spurts. Then
a pilot had to quit using it for a while because the twenty-six percent added
boost to the engine would burn it up if used too long. This pilot used his
methyl injection very advantageously to keep me from shooting him down. When his
methyl was gone, he dived to the deck and dropped into a tar pit that was about
500 feet deep and wide enough to fly a fighter in a tight turn. I got a few more
strikes on him. A portion of his vertical stabilizer and one wingtip flew off.
Unfortunately I was getting low on gas and had to break combat and head for the
North Sea, and England. After two more circles in the pit I pulled up and flew
away to the west. I looked back over my shoulder to see the FW-190 going the
opposite way, waggling his wings as if to say, "I'll see you tomorrow and we'll
go at it again."
A few years ago the American Fighter Aces had their annual reunion at Maxwell
AFB near Montgomery, Alabama. The base commander invited five of the top living
German Aces. The first day I arrived in a large hall where over one hundred
Maxwell and AFA officers were gathered. Ace Gabreski, the highest scoring living
USAF ace, who is a friend and a man that I admire to the hilt, was talking with
the German Aces, along with several other US Aces. One subject was the German
attitude and tactics relating to the P38. Gabby saw me come to the opposite side
of room, waved and hollered for me to come over. He introduced me as the highest
scoring P38 Aces in Europe.
When I shook hands with German General Adolf Galland, I said, "Adolf, did you
ever shoot down a P38?"
He said, "Yah, I shoot down eight."
Then I asked him if any of his pilots told him about a fight in a long nosed
FW190 in late 44 against a P38 that wound up in a huge pit with water and two
crashed P38s on the bottom. I described what had happened and the strikes I got
on the long nosed 190, then told him that when I ran low on gas and had to
leave, the German pilot had waggled his wings as he flew away in the opposite
direction. I was using my hands and looking down as I talked and wasn't watching
Galland. When I looked up, he was pale white.
He said, "You son of a squeak! You dom neer keel me dat day!"
Holy Mackeral! All the pilots that heard our conversation bellowed their
surprise, including me. Adolf wouldn't let me out of his sight for the rest of
the day, asking me how I got the P38 to do what I had explained was my clover
leaf in a tight Lufbery "Fight to the death" tactic. He wanted to know how I
trained our pilots and had many other questions about tactics."
Now, the three men involved here, Gabreski, Galland, and Lowell, are all decorated veteran combat pilots, held in high regard in the world of fighter pilots. What would any of the three have to gain by lying, when the truth had already made them heroes and legends? What reason is there to believe that they were too stupid to know what they were talking about?
I am fortunate to know several World War II pilots, and hold them in the highest regard, in my experience they have more honesty and integrity than 99% of all people I've ever met. Maybe I'm an old fashioned hillbilly redneck, but I have no patience for anyone who questions the honor, intelligence and integrity of those men.
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Hm... Well, I wonder if somebody here rates Martin Caidin's books better source than USAF documents? Also Bodie's book is a bit questionable specially in the case of the those high engine ratings.
The initial climb rates at WEP (67") for the P-51 are around (based on several tests):
P-51B without fuselage tank 3600-3900fpm
P-51B with fuselage tank 3500-3700fpm
P-51D with Fuselage tank 3400-3500fpm
And if we want fair comparison against the P-38 at 1725hp (grade 150 fuel, as rated by Allison and probably required by Lockheed too) then the P-51 had WEP +25lbs (80") and initial climb rate around 4500-4800fpm.
gripen
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I happen to live near the Consolidated Vultee plant in question it was in Nashville TN, and produced 113 planes. It was not a new plant, but a standing part of the Consolidated factories. The War Production Board just didn't get their act together. The P-38 was also a difficult plane to build, and required precision jigs for assembly. The USAAF needlessly tied up Lockheed engineers and fabricators on pointless projects that the USAAF mismanaged any way, when they could have been used to set up manufacturing facilities here at Consolidated Vultee, and train the employees to build the planes. Had this been done however, they could have stopped production to retool for the P-38K, and several other enhancements Lockheed had developed.
As far as the USAAF having a desire for the P-38, and wanting more, there were a few thousand on order when the war ended. Also, the War Production Board considered the P-38 to be so important and essential that they refused to tolerate ANY delays in production, for any reason. This pretty well refutes any theories that the USAAF didn't want any more P-38's. Only when the war ended and they couldn't AFFORD the P-38 did they cancel their orders.
Whoever said they were producing F4F Wildcats for escort carries is correct.
Documentation of 64" of manifold pressure can be found in the Lockheed charts in the article "Der Gabelschwanz Tuefel" by Dr. Carlo Kopp, on C.C Jordan's website "Planes and Pilots of World War II".
I have been corresponding with Dr. Kopp, Warren Bodie, and C.C. Jordan, while assisting on a project regarding the death of Major Thomas B. McGuire. The three gentlemen mentioned above were kind enough to verify those figures as correct. Mr. Jordan has a source at Lockheed Martin, and Mr. Bodie was an engineer at Lockheed for a few decades.
As far as how to deal with the German fighter in a dive while flying the P-38, Lowell said you could roll and pull a G or two and follow any prop fighter in a dive. Heiden never mentioned his maneuver, but said he could tailgate any German plane in a dive flying a P-38J with dive flaps. Heiden also said the the P-38L could do anything as well as the P-51 could, and he flew both of them.
The main part of your argument is, and always has been, that critical Mach is the single over riding factor in determining capability. I don't buy that.
You also state that in YOUR opinion, critical Mach is the reason the 8th AF abandoned the P-38. I don't buy that either. Although the compression problem was a factor, it was the other problems that the 8th complained about. Cold cockpits, engine problems, difficulty with maintenance, level of difficulty for the pilots, and the continual lack of planes and spare parts.
While not the same as military command, I have management experience, which is where the problem lay in the 8th AF. Actually, I did face a situation where a group of employees I was asked to manage failed to achieve the level of performance that other people using the same equipment achieved. The first thing I did was look at training and leadership. When motivated and qualified people were placed in positions of leadership, and the others were properly trained on the equipment, this same basic group performed as well as or better than any other. Anyone with common sense could have seen what I saw, and done what I did. Basic troubleshooting, nothing more, and certainly nothing special. I came to that position with a high school diploma and common sense, and replaced a guy with a college degree in managment.
Now, if I had plenty of P-51's, which the 8th did not, until mid 1944, I would use them. But if I did not have plenty of P-51's, and needed the P-38's, I'd figure out what was wrong and set about fixing it. If I had successful P-38 pilots, I'd be making them group and squadron leaders, and passing every bit of knowledge they had to every P-38 pilot I had, teaching and training other pilots constantly. If I had crew chiefs who could keep P-38's in the air, and didn't lose engines, I'd have them teaching the rest every waking second they weren't working on their plane.
The truth was, the 8th desperately needed those P-38's, and failed miserably at getting the full potential from them. Poor management and tactics in the 8th were the rule, and not the exception. The failure of Spatz and Doolittle to place successful pilots like Lowell, Ilfrey, Blumer, Heiden, and a host of others, in positions of command and authority, and allow them to get the problems solved, instead of complaining that the P-38 just couldn't get it done, speaks volumes, especially when those pilots were successful, even against the best Germany had to offer, while flying the P-38, a plane the 8th considered second rate.
The 8th had the P-38 in their inventory, and good pilots who proved they could beat anyone and anything the Germans could throw at them in the P-38. The 8th chose to ignore this fact, and replace the P-38, instead of finding out what the rest of the 8th was doing wrong when they flew the P-38.
When a man consistently succeeds in a machine you think is second rate, if you are smart, you take a much closer look at his ride. At least if you're smart you do.
I live in the world of must win competition. I make my living by producing winners on the race track. When something comes along that I know is going to give me a real advantage, I use it. I don't install second class parts on a race engine and expect it to win, and complain when it doesn't.
For the USAAF to send a pilot into combat in a plane they KNEW could be improved, and they chose not to improve it, borders on criminal mis-management. Sending a soldier into battle with a weapon that could and should be better is wrong. To deny a pilot any advantage that could save his life is absurd.
In the end, the decision to cease production of the P-38 came down to one thing: MONEY. The P-38 cost the USAAF over $130,000 per plane. The P-47 around $78,000, and the P-51 around $62,000. Only the Chance Vought F4U remained in production after the war ended for any real length of time. There were already tens of thousands of piston engined prop driven fighters in the U.S. inventory, when the USAAF only wanted well less than 10,000.
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Originally posted by gripen:
Hm... Well, I wonder if somebody here rates Martin Caidin's books better source than USAF documents? Also Bodie's book is a bit questionable specially in the case of the those high engine ratings.
The initial climb rates at WEP (67") for the P-51 are around (based on several tests):
P-51B without fuselage tank 3600-3900fpm
P-51B with fuselage tank 3500-3700fpm
P-51D with Fuselage tank 3400-3500fpm
And if we want fair comparison against the P-38 at 1725hp (grade 150 fuel, as rated by Allison and probably required by Lockheed too) then the P-51 had WEP +25lbs (80") and initial climb rate around 4500-4800fpm.
gripen
Bodie was a Lockheed engineer. I'll ask him about those ratings if you like. He may or may not answer, he's quite an ornery old cuss.
All though they could not prove that it didn't work, the USAAF did not like 64" of manifold pressure on the Allison and did not specify it. However, Lockheed and Allison did several tests and it worked.
For some reason you think a Merlin could gain 13" inches of manifold pressure by going from 130 to 150 but an Allison could only gain 4"? Possibly true for a P-38H, but not a P-38J or L with core type intercoolers in the chins.
Want a fair and interesting comparison between a P-51 and a P-38? Try comparing a P-51K with a P-38J-5-Lo. The P-51K had the same basic prop as a P-38, but was otherwise the same as a P-51D, Packard Merlin and all. Go look for the data.
Want to know how good the P-38 could have been, if the USAAF and the War Production Board had let Lockheed do their job? Take a look at the P-38K.
The P-38K had an initial climb rate of 4800 FPM at MILITARY POWER, not WEP, while FULLY loaded. It could take off from a standing start and reach 20,000 feet in 5.0 minutes. Top speed, over 430 MPH at 29,600 feet, again, at MILITARY POWER, and not WEP. While the V1710 F-30 engines used in the P-38K were rated at 1875 horsepower at WEP, their military power rating was little, if any higher than the F-17 engines in the P-38L. The props were expected to increase range by 10-15% due to enhanced efficiency. They also eliminated the failures associated with the Curtiss Electric props. Hell of an airplane, wasn't it? Would have gone into production in June of 1943, no later than the first week of August.
You want to tell me again how I should trust the USAAF to be smart, fair, and unbiased?
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Renegade Savage,
Hm... Now I must wonder a bit because there was 62,4" in that web site you claimed earlier (and CC/Widewing claimed 62,4"@3200rpm here), I quess a debate about 3200rpm here has changed history ;) ... and I do not qualify web sites any better than Martin Caidin as a source. Anyway, noone has argued if such ratings were tested but were those ratings used in service and was there required fuel available? Also claim for critical altitude at 64" is questionable. In the case of the P-51 use of the grade 150 fuel and +25lbs MAP is well documented by the RAF and other sources.
The Merlin could handle high manifold pressures better than the V-1710 because it had lower compression ratio (6,0 vs 6,65) and actually also Allison changed to the 6,0 compression ratio in their later F and G series developements. Also it should be noted that even 60" was critical for the P-38J as seen in practice.
The America's Hundred thousand does not support at all your claims about the propeller of the P-51K. Go look for the data.
gripen
[ 12-07-2001: Message edited by: gripen ]
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Hey look... we have a book now!!!!!
xBAT
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A question: would it be possible to accidentally overboost your engine in a dive?
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Originally posted by gripen:
Renegade Savage,
Hm... Now I must wonder a bit because there was 62,4" in that web site you claimed earlier (and CC/Widewing claimed 62,4"@3200rpm here), I quess a debate about 3200rpm here has changed history ;) ... and I do not qualify web sites any better than Martin Caidin as a source. Anyway, noone has argued if such ratings were tested but were those ratings used in service and was there required fuel available? Also claim for critical altitude at 64" is questionable. In the case of the P-51 use of the grade 150 fuel and +25lbs MAP is well documented by the RAF and other sources.
The Merlin could handle high manifold pressures better than the V-1710 because it had lower compression ratio (6,0 vs 6,65) and actually also Allison changed to the 6,0 compression ratio in their later F and G series developements. Also it should be noted that even 60" was critical for the P-38J as seen in practice.
The America's Hundred thousand does not support at all your claims about the propeller of the P-51K. Go look for the data.
gripen
[ 12-07-2001: Message edited by: gripen ]
The data and charts came from the Lockheed Martin archives. As I stated above, this was provided by a source currently employed by Lockheed Martin, to C.C. Jordan, and Warren Bodie was until the early to mid eighties, an engineer at Lockheed. Whether it is published in your favorite book or not is irrelevant. Martin Caiden and your opinion of him has nothing to do with this. Books are not by definition any more correct or reliable than a website. Accuracy depends on the thoroughness and honesty of the person who does the research, not what media it is published in.
Why is it you use a comma where a decimal is appropriate? As far as compression ratio is concerned, 0.65:1 difference (6.0:1 as compared to 6.65:1) does not allow for a 20" (10 pounds of boost) difference in manifold pressure. Anyone who believes that it does has no idea what they are talking about. That difference in compression ratio will barely account for 2" difference in manifold pressure, at best.
The argument concerning the ratings has more to do with whether or not the USAAF was fair and honest, and whether or not they knew what they were doing, than what was actually used. It was the contention of Lockheed and General Motors Allison division that the USAAF was unfair and biased in their ratings, and has been for decades.
On the subject of testing and rating engines, one thing you should know is that the tests and results are only consistent and reliable if the proper conditions are met and maintained. An engine dyno is a very funny piece of equipment. Readings may be so easily manipulated by the person operating the dyno as to render results worthless. Other than the advent of computer controls, the engine dyno has not changed in over 80 years, it is merely a water brake with a device to measure pressure or force exerted in a rotational direction. I own and operate a Kahn 1000 horsepower, 10,000 RPM water brake dyno, it works exactly the same as the Heenan Froude dyno used to test aircraft engines. I can demonstrate for you the fact that torque readings (horsepower equals torque in pounds feet multiplied by RPM and divided by 5252), and the threshold of detonation can be easily manipulated by a minute adjustment of the damper valve on the dyno. An adjustment so small you would not even know I turned the valve at all, even if you were standing 1 foot away and staring at my hand. Considering their proclivity for ignorance and bias, I trust the USAAF and their dyno results less than you trust Martin Caiden, and for good reason.
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Commas are used instead of periods to indicate the decimal point in European countries.
This is apparently why the international standard for digit groupings is a space, not a comma (e.g. 1 000 instead of 1,000).
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Renegade,
"Top Guns"... I think I had this book many years ago. I do remember having a book with the story you quote but lent it to a friend almost 10yrs ago and never saw it again. Does the book end discussing Randy Cunningham's victories? Anyway, if the same book, I also remember a story about a P38 pilot challenging a Spit pilot to a friendly duel over England who wins out over the Spit. That's probably the better story to tell. <g> I'll have to look into this title and see if I can't replace it.
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Hi grippen!
can you tell me which book and or test you are quoting with the 3,500 and up to 4,800 fpm climbs for the P-51B/D? if it is a test that somebody posted on a web site could you give me the url please? I do have a lot of mustang books, but most are old. Roger Freemans book on the pony may be of interest to you. not only does it state the mustangs good points, but it also goes into details on its vices and maintenance problems. I think all planes had their problems none more than any other. Roger Freemans book gives the cronological order of problems and restrictions placed on the mustang during the war. It is a good read and not too expensive.
http://www.classic-books.co.uk/books/ae.html (http://www.classic-books.co.uk/books/ae.html)
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Renegade Savage,
Well, the problem is that they have claimed 1725hp rating as standard but so far there has been no evidence. Another problem is that CC/Widewing has claimed several different versions of this rating (60"@3000rpm, 62.4"@3200rpm, 64" something 3000rpm I quess) so which one to believe and why claims tend to change?
The V-1710-G6R/L (6.0:1 compression ratio) was rated dry for 74"@3200rpm with grade 115/145 fuel, very comparable to the Merlin at 80"@3000rpm with grade 100/150. So at least 10" can be explained by the ratio change and maybe more because you have not claimed RPM nor fuel for that 64" rating, so, please do. Allison claimed 1725hp at 3200rpm with grade 150 fuel, Aircraft Engines of the World 1947 claims 60" for this rating. So what's the exact rating and fuel?
BTW You don't have explain your opinions about American soldiers at the Wright field during WWII in your every post. I believe everybody allready know how much you respect these veterans.
gripen
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bolillo_loco,
Books,
Tim Mason: The Secret Years
David Birch: Rolls Royce and the Mustang
Ken Delve: The Mustang Story
Jeffrey Ethell: Mustang - a Documentary History
Archives:
A&AEE reports are easy find from the PRO (http://www.pro.gov.uk/)
There is a good library in Boscombe Down too.
Lot of USAF records are available from the NARA (http://www.nara.gov) and AFHRA (http://www.au.af.mil/au/afhra/)
Then there is some stuff which are a bit conf...
gripen
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Thanks grippen the books are added to my get list. would you have any specific ulrs for the naca data? I am sure you have been there already and there is a ton of junk to sift thru, takes days and days :(
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bolillo_loco,
Well, I don't really know what you wan't, for me there is lot of fun stuff (in fact too much). Anyway, this (http://naca.larc.nasa.gov/reports/1947/naca-rm-a7c24/) is a good report about dive recovery flaps.
There is a lot of NACA stuff around which is not even listed in their computer index, so just keep your eyes open.
gripen
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Hi Hilts,
>But one thing I take exception to is people who persist in questioning the honor and honesty of decorated combat veteran pilots.
Look at it soberly: There's information readily recognizable as wrong in that report, for example the description of the function of MW50 injection. Noone would call Lowell a liar for that - I'm quite confident that his explanation matched both his observations and whatever intelligence he had on the Focke-Wulf.
I'd put a bit more trust in the veterans than you apparently do - it's not like the entire story would collapse if you'd try to resolve the major contradictions. Just a different estimate of the date (which might have been confused), allowing for misidentification of the "long-nose" Fw 190 (which happened very often in early 1944), would also make it a possiblity that Galland had some more freedom and a legitimate interest in the Reichsverteidigung, making it much more likely that he actually personally flew a mission. If the wrong date was used to verify the target, the process of checking the story might have unintentionally introduced an error, and if the target was, say, the Ruhr area, open-cast mining wouldn't be unusual at all.
That's just speculation to show how a minor mix-up could have created the contradictions we're observing, and common sense should tell you that there's nothing dishonorable about it.
I don't know if you read about Urban Drew and the destruction of the unique Bv 238 giant flying boat which was attributed to him. His claim had been a Bv 222, historians said it was the Bv 238, but after Drew years later recognized the history of the Bv 238 destruction conflicted with his memories of the incident, and helped with further research, it was found that he had actually destroyed an equally unique giant flying boat that the Luftwaffe had captured from the French, and intended to use for the insertion of special forces.
That's an excellent example for a well-researched story that was considered correct for years with good justification - and yet, the truth was entirely different, and finally revealed by taking both the veteran's memories and the contradictions in the accepted story seriously.
I don't expect the contradictions in Lowell's story to be due to similarly spectacular coincidences, but I have great faith that both documented facts and the veterans' memories will fit perfectly once you find out how to match the puzzle pieces.
I really admire how Urban Drew, discovering the contradictions between accepted history and his memory of the events, decided to push for clarification! It would have been easy for him to accept the myth instead.
Regards,
Henning (HoHun)
>12-06-2001 07:08 PM
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...allowing for misidentification of the "long-nose" Fw 190 (which happened very often in early 1944)...
Definitely the case. 4th FS (52nd FG) Spitfire pilots in February 1944 reported two encounters with four-ships of inline Fw 190s over Nice harbour in the Mediterranean.
One possibility which would allow for Galland actually flying a long-nosed 190 might be the pre-production service test models, which were around in early 1944. Given his rank, I'd imagine he could have gotten one without too much trouble if he intended to personally fly.
When the actual fight started, it wouldn't be too much of a stretch for the P-38 pilots' identification process to go as follows:
1) Correctly identify the formation as Fw 190s.
2) Focus on the lead plane and correctly identify it as a "long-nosed" 190.
3) Call out "Bandits! Flight of long-nosed 190s!", not bothering to look closely at the other 190s in the formation.
4) Fight starts, and everyone's too busy to worry about subtle differences anymore.
(Wonder if I'll regret entering this discussion... ;))
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Some A´H fuel to the fire....'
Ïf it's accepted that *type* could be seen at relativly long raange (Spit/Fw/P38) bit *marque* was hard to see, what implications does that have for an icon system?
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Hi Bolillo_loco,
>he states that the second LO series of 38L production batch used this power as standard. not the first 38L series which used the same power limitations as the J series.
Would that be the P-38L-5-LO and the P-38L-15-LO respectively? I'm not quite sure about the exact designations.
>Tony levier states that mach .72 was completely safe with dive flaps for the P-38 and many manuals and pilots stated that recovery was effortless with dive recovery flaps. also dives from 20,000 ft are said to have been no problem for the 38 with or with out flaps. the P-51 series is stated to have a max safe dive speed of mach .75, is there that much of a difference?
The corresponding number for P-38 with dive brakes and P-51 were Mach 0.68 and Mach 0.75 respectively. This was the placarded maximum where the airplane was still controllable. You could exceed this Mach number, which in both aircraft would virtually freeze the controls, and in the P-38 induce a heavy nose-down trim.
Mach 0.72 might have been safely attainable with trim properly set before the dive by an experienced test pilot following instructions from the company engineers, but the much lower limit in the pilot's manual made sense since if you exceeded Mach 0.68 in the heat of combat, results could be catastrophical. It wasn't as bad in the P-51 - diving to lower altitudes, the constant true air speed would translate into decreasing Mach numbers, so it would be possible to pull out again at lower altitude.
Eric Brown, a British test pilot working for the Royal Aircraft Establishment which was leading in high speed research during WW2, refers to "maximum safe Mach number" and "maximum tactically useful Mach number".
Maximum tactically useful for the P-38 versus the P-51 was Mach 0.68 at best, versus Mach 0.75 respectively. Maximum safe was Mach 0.72 versus Mach 0.86 (quoting Gripen's Borsodi number).
Another Mach number related topic that Gripen first mentioned in another thread is that at increasing angles of attack, the critical Mach number dropped. The result is that manoeuvrability suffered - and it was worse for the P-38 at great altitudes than for the P-51.
Regards,
Henning (HoHun)
>posted 12-07-2001 12:03 AM
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Hi Hilts,
>Documentation of 64" of manifold pressure can be found in the Lockheed charts in the article "Der Gabelschwanz Tuefel" by Dr. Carlo Kopp, on C.C Jordan's website "Planes and Pilots of World War II".
Thanks, I found it. I had thought you might have a primary source, though, like the manufacturer's engine power charts we have seen posted here for the Jumo 213 or BMW801 engines.
Here's a quote from Kopp's article:
"The two Allison V-1710F-30 V-12s had a 5.5 in. bore and 6.0 in stroke, providing a compression ratio of 6.5. These drove Curtiss Electric constant speed props via a 2:1 reduction gear, delivering 1,475 HP military and takeoff ratings at 3,000 RPM, or 1,612 HP maximum rating at 3,000 RPM and 60 in. of manifold pressure. Some later engines are described as delivering up to 1,725 HP WEP rating."
His statement regarding the 1725 HP engines - which would indicate the 64" Hg manifold pressure according to the graphs - seems very cautious to me. "Later" could imply that these were engines that weren't incorporated into series production, for example, or even that the quoted top speed graph was only a calculated projection.
>As far as how to deal with the German fighter in a dive while flying the P-38, Lowell said you could roll and pull a G or two and follow any prop fighter in a dive. Heiden never mentioned his maneuver, but said he could tailgate any German plane in a dive flying a P-38J with dive flaps. Heiden also said the the P-38L could do anything as well as the P-51 could, and he flew both of them.
Lowell's tactics limit the speed build-up during a dive, which is a useful manoeuvre of course. If attacking a Luftwaffe pilot who just dives away without having to care about excessive speed build-up, the P-38 will be left behind anyway. That's what Gerald Brown meant by his statement
"Early on the German, like a street bully, could pick a fight and then break it off against the P-38. He couldn’t do that with a P-51."
Heiden's general statement doesn't mention operational altitude. Guppy's P-38 pilot quotes (from Corky Smith and Stan Richardson) are more specific, and both give the high-altitude advantage to the P-51, agreeing with Gerald Brown in that respect.
>You also state that in YOUR opinion, critical Mach is the reason the 8th AF abandoned the P-38. I don't buy that either. Although the compression problem was a factor, it was the other problems that the 8th complained about. Cold cockpits, engine problems, difficulty with maintenance, level of difficulty for the pilots, and the continual lack of planes and spare parts.
The problems you describe certainly played an important role in the 8th Air Force's disappointment with the P-38. However, both the P-47 and the P-51 had teething problems, too, but they were fixed without abandoning the aircraft.
The reason I'm convinced critical Mach number was the decisive factor is that its problems were considered insurmountable by the 8th Air Force's leadership (according to an 1996 USAF research paper by LtCol Daneu). The problems you have described could have been fixed - in fact, it's a central point of your argument that they could! - but the low critical Mach number would have required the design of a completely new airframe.
Regards,
Henning (HoHun)
>12-07-2001 12:47 AM
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I don't see any major contradiction in Heiden's statement.
The main reason German fighters could escape at will was that the P-38s didn't pursue. That was because the pilots weren't confident they could recover from a dive, not because the Germans had a higher maximum dive speed and would eventually outdistance them.
With the dive flaps, the P-38s could pursue and break off the chase if they got into compressibility trouble. Obviously, the German fighter would pull ahead in the end. But if the P-38 was locked on his tail already, it might well stay there long enough to get the telling burst in--and if the German levelled off too soon, confident that he'd shaken off pursuit (as he would with an early P-38), he would be in for a very big shock.
I'm pretty sure that's what Heiden meant--the Germans still had an advantage in the dive, but it was no longer a guaranteed escape.
(Against the P-51, of course, the diving pursuit could be maintained indefinitely, assuming no great strength disparity between the pilots.)
By the way, the L variants of the P-38 were the L-1 and L-5.
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Originally posted by batdog:
Hehe..TAC is sneaky. The J is faster AND lighter as it doesnt have quite the fuel load of the L...
xBAT
P.S. Yea a GREEN 38 would be nice.
Hehe, just wait till they put the second effect of the dive flaps on the 38 and you'll see how much of a difference they make.
The J is marginally faster, and it wont have the dive flaps, so it'll be a squeak to fly vs almost any plane if they just get on to diving away. Think about it... the L will be able to follow you in OR make you auger if you follow it on a high speed dive near the deck... so people WONT follow the WHITE 38 on dives. But they see a GREEN 38 , oh ho, dive dive dive!.
"The pilot was looking down at me as he eased
ahead and close above me into sure death, unless he could take violent evasive
action. He split-Sed and I followed him. He nearly got out of my sight because
the P38 high-speed compressibility problem kept me from staying with him in a
vertical dive. I stayed out of trouble by doing a vertical barrel roll to pull
several Gs and keep my speed under control."
BTW, this is something that all 38 pilots in the MA should know. Im horrified at the number of 38s diving from 20k to 4 ft under because they dont pull g's on the dive.
:eek:
[ 12-08-2001: Message edited by: Tac ]
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Hi Hohun, I could not disagree with you or grippen more. If you have the pilots manual look at the section for diving. It clearly states that mach .675/.68 is the placarded limit with out dive flaps and that with the dive flaps extended it may be exceeded by 20 mph. It also states that trimming is not neccesary nor recomended, remember the P-38 unlike all other single engined a/c did not need to be trimmed and re-trimmed for speed changes. dive flaps made recovery much easier and efforless even for green pilots. read the above attachment that somebody else posted earlier. it looks like an official document to me. I agree that w/o dive recovery flaps, only experienced pilots like tony levier and other calm pilots could bring a 38 out of a dive at high speed, but again with flaps the plane recovers by itself.
Americacs hundred thousand states that several pilots flew the 38 with dive flaps and all were very pleased with the results, "recovery is effortless" it also goes on to say that dispite this most ranked it last in dive control and dive stability. I tend to agree with what most of renegade savage (but not all) says. I feel that the rumor mill resulting from failures of the 38H followed the 38 thru all its models, dispite fixes that brought the 38 up to par or did away with the problem all together. If you look at all the complaints on the P-38, unreliable engines, one generator, run away props, turbo regulator problems, cold cockpits, dive stability, slow rate of roll at medium to high speed, power restrictions at altitudes over 20,000ft, the P-38J-25-LO
(some of these problems were fixed with the first introduction of the 38J-5-LO) and
later models either solved the problem completely or brought it up to par with other a/c.
The test were the 38 with dive recovery flaps was tested against the P-47D in a dive levier stayed with the 47 or only lagged behind by a bit and then pulled right aside of the 47 after the dive shows that the dive recovery flaps broght it up to par with most a/c. P-47s also had dive recovery problems. late D models were fitted with dive recovery flaps. Levier stated that he was good friends with the P-47 pilot who is considered to be an expert on the 47 type, stated that after the last dive when the 47 really poured it on the P-47 pilot was beat black and blue between the thighs by the stick because it was thrashing about wildly in the cockpit.
The tests where P-47s, spitfires, and P-51s were all dove well beyond mach .8 seem to all have had special preperation. The P-47 for example had a specialy fitted propeller because in high speed dives no matter how sound the airframe is the propeller becomes the limiting factor. I have seen the high mach number dives for the mustang. they had the propeller completely removed for this dive and other special preperations were done. The mustang is well known for structural weakness when flown at full weight. it is designed for +8 g max at 8,000 lbs, this is 2,500 lbs heavier than the B/C/and D model. americas hundred points out the test where the P-51 was damaged as a result of the pull out from a mach.81 dive and the mustang had to be scrapped. Roger Freemans book points out several of the mustangs airframe weaknesses where several 51s had to be scrapped due to structural failures because of pull outs from high speed dives.
I could not agree more that the 38 was far to complex and one had to know a lot about it. I think as a result of this the rumor mill and green pilots and many people today just lable it as laim and maybe do not want to do research beyond that.
Thanks for the debate guys.
[ 12-08-2001: Message edited by: bolillo_loco ]
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Hi Hilts,
>All though they could not prove that it didn't work, the USAAF did not like 64" of manifold pressure on the Allison and did not specify it. However, Lockheed and Allison did several tests and it worked.
I'm sure the USAAF had well-defined criteria for acceptance of an engine setting, including bench run reliability tests.
I think to find out about the reasons for the USAAF not adopting the 64" Hg power setting, we'd have to determine the USAAF requirements and whether Lockheed or Allison actually met them.
For example, the 64" Hg setting might have worked in practice, and even worked reliably, but still the USAAF never formally approved of it. If the reason was that the manufacturer never proved the engine setting according to the USAAF criteria, the contradicting performance figures we're finding everywhere would seem unavoidable.
Then, the next question should be: Why was the power setting never formally approved of?
Regards,
Henning (HoHun)
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Well, this has became far too long discussion. Anyway, couple comments more :)
Generally I believe all pilots comments, but those tend to be so contradictory that it is pretty difficult to say something surely based on them; pilots tend to favour planes they liked most and comparison specially with enemy planes is difficult because skill of the pilot vary a lot. By collecting enough pilot's comments and pickingup just those which support your argument, you can "prove" what you want. A good example of this is the Bf 109 out turning Spitfire stories and in this discussion I see similar phenomena.
I hope that everyone interested about diving qualities of the P-38 download that NACA document I pointed to bolillo_loco. Document explains pretty well how dive recovery flaps worked and how pitching moment changed at various mach number. Also it should be noted that above mach 0.7 the pilot was more or less a passenger in his plane even with dive flaps, Tony Levier wrote that the plane acted like a mad demon at compressebility speeds. The dive flaps added a lot of drag to keep the plane out dangerous speeds and made safe pull out possible at faster speeds than without them. But as the manual notes anything more than 45 degrees in dive at high altitude was not safe even with flaps.
I collected data about weights (AHT) at various combat loads (I wonder where from that bollilo_locos 10500lbs comes or is it 5500lbs?) and safe loading factors of the P-51 assuming safety factor 1,5 and linear estimates for loadings (which actually is not the right way but good enough here):
P-51A 8000 lbs 8.0g
P-51B no fuselage tank 9077 lbs 7.27g
P-51B fuselage tank empty 9332 lbs 6.89g
P-51B fuselage tank full 9842 lbs 6.46g
P-51D fuselage tank empty 9698 lbs 6.58g
P-51D fuselage tank full 10208 lbs 6.16g (AHT 6.3g my estimates are conservative)
P-51D 220 gallon external fuel 11708 lbs 5g
Assuming that in combat fuselage tank is at least near empty, we can see that safe g load factor is more than 6.5 (breaking load factor 9.75). Generally load factors above 6g were rare in combat except accidentally for example in the case of the stick force reversal (too much fuel in the fuselage tank). Borsodi trimmed his plane nose heavy and was able to pull out without over stressing his plane.
gripen
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Hi grippen, I just meant to say about 2,500 lbs lighter, thank you for correcting me 10,200lbs sound quite correct. I moved back from texas last month and I lost my books :( now I must replace them.
I could be wrong when I say this, but I feel that people believe that the P-38 was the only plane that became unsafe at speeds beyond mach .7 with or with out flaps. I had two books which stated mach .675 buffet began and at mach .74 nose dive tendency became termanal. this is with out dive recovery flaps. the flaps added some more speed to the dive, however I do not believe it was anything great in terms of speed. it looks like mach .05 perhaps, but nothing more.
the P-51, P-47, corsair, fw-190D, bf-109 series all were probably pretty unsafe at airspeeds beyond mach .75. from what I have read it seems to be so. even the mustang with its laminar airfoil it is highly cautioned in all pilots manuals not to exceed mach .75. beyond that the a/c is no longer safe and compressablility begins by the plane starting to become uncontrollable. the problem I see with the 38 is that in the initial push over from 30,000ft at a low to medium ias the a/c is going to pick up speed much more rapidly than a mustang and that is why it is so critical to be careful in the 38 w/o flaps. with flaps if compression is hit and the a/c is no longer in control the flaps atleast make recovery possible when it hits lower altitude. before this the pilot and plane were lost. this sounds familiar to all a/c I have mentioned above. 47's and 51's were all lost to compression and any of the american types that could reach or exceed 400 mph ias at 30,000 would all dive straight into the ground if they were power dove from 30,000 ft and 400 mph ias. if you dont believe me go and look at the P-47 training film at zenos warbird videos on high alt maneouvering in the 47. it lists the altitude needed to recover from a dive started at different speeds tas. from 30 k and at 400 mph tas the 47 will go straight into the ground. if you have americas hundred thousand go to the part on the 47 on pilots comments. one pilot resorted to firing all guns in an attempt to slow down his a/c because his a/c refused to respond due to compression in a high speed dive. it wasnt until he rode the plane all the way to the deck as a passenger not a pilot that the plane did respond.
all the 400 mph + tas high performance a/c flying in ww 2 battle trim (ie no special attention for a special test to make it dive better) will crash into the ground when begining a power dive from high ias at 30,000 ft.
thanks for the info grippen. going to get those books you listed as soon as I replace my others. and thanks for the debate it was interesting.
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bolillo_loco,
Hm... I wonder where you have got a idea that the P-38 pick up speed much more rapidly than the Mustang at high altitude? Due to better propeller efficiency, exhaust thrust and lower drag the P-51 certainly accelerated better at high altitudes than the P-38. And yes, many P-47s and P-51s were lost due to comressebility (mostly because incorrect use of trim or stick force reversal), but if a pilot knew what to do, he could start dive from high altitude at high speed, enter compressebility speeds and recover safe. At least my copy of AHT does not support your argument nor other sources I have.
gripen
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:)
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Hi Hilts,
>The data and charts came from the Lockheed Martin archives. As I stated above, this was provided by a source currently employed by Lockheed Martin, to C.C. Jordan, and Warren Bodie was until the early to mid eighties, an engineer at Lockheed. Whether it is published in your favorite book or not is irrelevant.
It still would be nice to see the orginal data or charts, not only because they'd be more credible than a footnote in a secondary source, but also because they usually specify the exact circumstances with greater accuracy than secondary sources do.
Regards,
Henning (HoHun)
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Hi Guppy,
>Definitely the case. 4th FS (52nd FG) Spitfire pilots in February 1944 reported two encounters with four-ships of inline Fw 190s over Nice harbour in the Mediterranean.
Yes, that's exactly the kind of effect I was thinking of! I really wonder how Allied intelligence found out about the long-nose Focke-Wulf so early - many months before the type was actually finalized for production.
>One possibility which would allow for Galland actually flying a long-nosed 190 might be the pre-production service test models, which were around in early 1944.
Good suggestion! Since the fate of every Fw 190 prototype has been published since then, this might be verifiable. (I checked it once for the date orginally attributed to Lowell's story, and there was no armed Dora prototype available at that time.)
Regards,
Henning (HoHun)
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Hi Seeker,
>Ïf it's accepted that *type* could be seen at relativly long raange (Spit/Fw/P38) bit *marque* was hard to see, what implications does that have for an icon system?
Air Warrior, which just was closed, had a complete variant desctiption in the icon, Warbirds just had the general type.
This does have tactical implications as aircraft of different variants can have very different capabilities - to stay on topic, let me point out that P-38F versus P-38J is one of the best examples :-) -, and as you'd recognize newbies easily as they'd be bringing obsolete variants to fight.
Though you'd have to rely on visual recognition to discern the aircraft subtypes, which due to the lack of visual detail was only possible by the paint schemes, in some cases the paint schemes were so different that you'd know at a glance what you'd be facing - the P-38F was olive drab overall, the P-38J natural metal.
Still, I liked the general type icons better than the exact subvariant icons.
Regards,
Henning (HoHun)
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My point exactly, HoHun.
In fact, most of the books I've got on American A/C show that by 44 at least, any Jug, Stang or 38 you met, unless brand new, was very likely to be a patch work of colours as holes were patched, things were fixed and bits added from any thing an enterprising crew chief could find.
The point being you should have a way of saying "38!" from five miles away (I can recognise a Spit from inside a train carriage over five miles away - did it this summer), but I really don't believe you can tell _which_ 38 further than 1000 yrds.
It would be nice to have differeing marques of 38 in the game. I'd prefer not to have a bill board saying which one it was hanging over my head.
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Hi Bolillo_loco,
>If you have the pilots manual look at the section for diving. It clearly states that mach .675/.68 is the placarded limit with out dive flaps and that with the dive flaps extended it may be exceeded by 20 mph.
The AAF Manual 51-127-5 has similar information on the P-51D:
"It can be dived to beyond 75% of the speed of the sound before going into compressiblity.
[...]
As noted earlier, it is possible to come out of compressiblity safely i fyou didn't go into it too far. The most important thing to remember about this is that while in compressiblity, you have virtually no control over your airplane."
That's why the relative figures for comparing the P-38 to the P-51 are Mach 0.68 versus Mach 0.75 for a speed at which the aircraft is under control, or Mach 0.72 (according to Tony Levier) versus Mach 0.80. (Judging from Eric Brown's descriptions, Mach dives were conducted with small increments in Mach numbers until test results indicated the safe maximum had been exceeded. According to one of your posts, this figure was reached at Mach 0.81 when pullout - not the dive itself - resulted in airframe damage.)
>The test were the 38 with dive recovery flaps was tested against the P-47D in a dive levier stayed with the 47 or only lagged behind by a bit and then pulled right aside of the 47 after the dive shows that the dive recovery flaps broght it up to par with most a/c. P-47s also had dive recovery problems.
From all the single engined fighters that were used in numbers in the European theatre, the P-47 was the one with the lowest critical Mach number, and in fact it had a history of "graveyard dives" (as Eric Brown called them) not unlike the P-38.
Brown's tests revealed that the unmodified P-47D was limited to Mach 0.73, where it got out of control. If Tony Levier went to Mach 0.72 in the P-38, the Mach number difference of just 0.01 would match the observed results quite closely.
Just like you point out, later P-47D variants were fitted with a dive recovery flap similar to those of the P-38. That also meant the P-47 was ahead of the P-38 once again.
>Roger Freemans book points out several of the mustangs airframe weaknesses where several 51s had to be scrapped due to structural failures because of pull outs from high speed dives.
Structural strength is a topic only loosely related to critical Mach number - an airframe can be overstressed far below its critical Mach number. Of course, as a tactical move a dive is most useful if it ends with an undamaged aircraft in a safe place :-)
Regards,
Henning (HoHun)
>12-08-2001 08:34 AM
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HoHun <S>
Glad to see you
Thats all :)
NwBie :)
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Hi Hohun, you may be quite correct pointing out the 47 test against the lightning was one having a critical mach number of .73 w/o the dive recovery flaps because the book I have does not state which model 47D. It had to be a 47D with out the improved ailerons because the ones with out these the stick had a tendency to float about due to aileron ocilation at high speed if I am correct.
The pilots manual for the 38 however does state clearly that mach .68 is with out dive recovery flaps.
I still feel that any ww 2 type a/c was quite unsafe at any speed above mach .75 at an altitude above 15,000 ft. That is the opinion that I have gotten from what I have read anyway.
One thing I am convinced of is the P-38 is still quite a controversial a/c because all the threads get very long with many posts. I hope some day that we may get some more modern data from reliable sources.
I also would like to see hard original data for the 1,725 hp allisons for the 38L. I do not care if it is right or wrong. widewing said he knew warren bodie and perhaps he could get hard lockheed data, but as of yet he has not :(
[ 12-09-2001: Message edited by: bolillo_loco ]
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TAC... later versions of J had the dive flaps.
xBAT
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P-38 kept it's maneuverability at high altitude, it just entered compressability easier the higher you went. In real life if you started a dive above 20,000ft, you compressed but dives started below 20,000ft didn't compress. That's why the P-38 excelled in the PTO and MTO because operational altitudes rarely went above 15,000ft.
Originally posted by gripen:
Well, the P-38 of the AH might do that but the real P-38 losed it's maneuverability at high altitude due to comressebility. The combat flaps helped at low altitude and at low speeds.
gripen
[ 11-28-2001: Message edited by: gripen ]
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I know x-bat, the late j model was for all purposes an L with a J engine.
I want the non-dive flapped J model. Green is good!
"The combat flaps helped at low altitude and at low speeds"
Again, no. At high altitudes the combat flaps gave the 38 its greatest advantage. At hi alts fighters dont regain their E as quickly as in low alts, and if the battle became a turning fight at 250mph or so, the 38 would easily out-turn and out-accelerate the 109's and 190's while having full control of the plane... a 190 or 109 trying to match it would either stall out or be forced to dive away. At low alts it also helped a lot, but it didnt give the 38 an advantage as big as it did "up there"
[ 12-13-2001: Message edited by: Tac ]
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Ack-Ack and Tac,
Please consult manual and AHT. I wonder how many times I should point out that compressebility speed decreased when g load increased and Clmax decreased when altitude increased. These things are discused several times above too...
gripen
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Gripen, im talking at 250 mph when the flaps can be deployed. At hi alts it does give much more benefits to the 38 than they do at low alts.
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Tac,
Well, as noted earlier (several times) the Clmax decrease when altitude increases because air density decreases and also because relative mach number decreases (for same reason compressebility speed decreases when g load increases, note relation between g load and Clmax). At low altitude the combat flaps (and contra rotating props) made high lift coefficient possible for the P-38 and at low speed below 140-150mph IAS it could out turn planes like the P-51, P-47 or Fw 190 (but not planes like the Spitfire or A6M), at higher speeds (between 150-250mph IAS) the combat flaps helped too but mentioned planes could still out turn the P-38 because they could tolerate more g load at these speeds despite what ever Clmax they could reach (while Clmax and g stall value for a given speed are related, you can't compare them directly). At high altitude the P-38 can't reach those high Clmax numbers because decreased air density and also because compressebility restricts Clmax, while those other planes can maintain their relative maneuverability better because air density nor compressebulity does not restrict their Clmax as much.
To put long story short: The turning performance of the P-38 at low altitude was based on high Clmax which it could not reach at high altitude.
gripen
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(http://home.cfl.rr.com/wraithfleethq/pics/manuvr3.jpg)
[ 12-13-2001: Message edited by: Tac ]
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Tac,
Well, I don't see anything which contradicts my points, or do you? No one has argued that the combat flaps do not help at high altitude (if compared to without combat flaps) but the relative maneuverability (if compared to others) of the P-38 decrease when the altitude increases. Please consult forexample following report "Tactical Employment Trials on the Republic Airplane P-47C" AAFSAT 16th February 1943 (turning comparison between P-47C and P-38G).
gripen
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From the charts I've got, at 10,000 ft the P-38 has G limits comparable to the P-51's up to about 230 mph. If the P-38's G-limits increased further with decreasing altitude, it would have a definite advantage below 10k.
However, how useful is the maximum G-limit of the airplane (due to accelerated stall, compressibility or whatever) in determining sustained turn performance? No WW2-era airplane could maintain a turn at 6G without losing significant speed or altitude. Up at 30k, I wonder if even 3G could be sustained. (Not that I'm saying better instantaneous turn isn't an advantage, but it's sustained turn which matters more in a classical turning fight.)
I seem to recall that those tactical employment trials between the P-47 and P-38 were conducted at 25-30 kft. At those altitudes, the P-47C had much more power available than the P-38G, which would most likely have been the dominant factor in sustained turning ability. Moreover, the P-47 was generally considered the best of the USAAF fighters at such altitudes.
Another point in favour of the P-38 at low altitude is accelerated stall behaviour. If a P-51 pilot presses the limits too far down low, he spins in (the P-51 apparently wasn't known for giving lots of stall warning). The P-38, by all accounts, had much better stall behaviour and could be pushed harder without risking a crash.
[ 12-13-2001: Message edited by: Guppy ]
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Man.. then WHAT are we arguing about? :) All I said was that it helped the 38 "up there" more than at low alts.. and in a turning fight (that meaning sustained turning), which in essence "up there" is a stall fight, the 38 has an advantage. Yes, the others may turn a bit better (and thats if they not turning against their torque), but not sustained.
They'd spin/stall out or very wisely extend to regain E.
I guess we're both saying the same thing but havent noticed.. lol.
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Guppy,
Yeah, the P-38 could definately turn tighter (sustained and momentarily) than the P-51 at low altitude and at low speed, no one has argued otherwise here. But situation is different at high altitude because there Clmax limits the P-38 more than the P-51 and as noted earlier the P-51 (V-1650-3) has a lot better propeller efficiency and exhaust thrusts available, so at high altitude it has an advangate (sustained and momentarily) and the P-51 (P-51B with V-1650-3) also turned better than the P-47D at high altitude (sustained and momentarily).
BTW above about mach 0.6 the P-51 could reach higher lift coefficient than the Spitfire (according to RAE). About sustained turns it should be also noted that even at low altitude WWII fighters could not turn much more than 3-4g sustained, much less at high altitude.
Tac,
Well, I have been arguing that the P-38 was not particularly maneuverable at high altitude if compared to other high altitude fighters (like P-51 or P-47) because aerodynamic limits of the airframe and propellers. It seems that you have have been arguing that combat flaps helped more a high altitude, but no one has questioned that (actually I could do that if assuming high speed, but I don't care).
gripen
[ 12-13-2001: Message edited by: gripen ]
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Sure. I was just interested in defining "low speed." I think 140-150 mph is pretty conservative; I'd be more inclined to credit a moderate advantage below 200 mph (more like a sensible combat speed), with rough equality around perhaps 230-250 mph.
And at high altitudes, I have no problem accepting that the P-51B and P-47 had more power available up at 25-30k than the P-38 (particularly F/G and early H), which meant better sustained turns; just that G-limits don't necessarily tell the whole story.
By the way, I think this thread's going very nicely in terms of finding common ground... :)
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Pyro replied about 100 posts ago that he has made some durability changes, like this thread was about. Now what are the rest of the messages about...
// fats
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Hi everyone,
with regard to high altitude turning, let me point out that at 30000 ft, sustained turns can only be done at a very slow turn rate even at slow speeds. (At higher speeds, they look more like straight and level flight :-)
The Mach number is low (smaller than 0.5) at low speeds, so the P-38 probably doesn't suffer from a decrease of the maximum lift coefficient.
However, I don't think combat at that altitude will see many sustained turns. (A sustained turn at 30000 ft could be compared to a spiral climb at lower altitudes from a tactical point of view.) I'd rather think the better positioned side would hurl itself against the enemy formation, and the fight would quickly drop to lower altitudes with aircraft turning a medium speeds and negative excess power. As the page from the P-38 manual implies, lowering the manoeuvre flaps makes the P-38's wing less efficient, so the manoevre flaps are really meant for this kind of fighting, too.
In a defensive position, the P-38 probably could be considered quite manoeuvrable at the low and medium speeds this involves, but in the offensive, it wouldn't look quite that good since this requires higher speeds where it's less manoeuvrable. Additionally, the attacked Luftwaffe fighters would not engage it in a turning fight where the P-38 could employ its strengths, but rather dive away steeply so that the P-38 couldn't follow.
It's the same old story: "Turning doesn't win battles".
A better performing P-38 wouldn't have changed anything about that, which is why the 8th Air Force didn't consider it a good fighter. Doolittle had a brilliant technical mind, and he certainly knew what he was talking about when he called the P-38 "second rate".
Of course, that's from the 8th Air Force point of view where high-altitude capability was of critical importance - I imagine his verdict might have been different had he considered the P-38 for a different tactical situation!
Regards,
Henning (HoHun)
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Gubby,
Well, I'd like find a reliable flight envelope for the P-51 to say surely what happens between 150-250mph IAS (BTW 250mph IAS at 30k is certainly at compressebility area under g load in the case of the P-38). I have seen some in the net but these do not behave like they should (as noted earlier I have some wind tunnel data for comparison). Theoretically it's pretty easy to calculate flight envelopes from the Clmax data but results will be unaccurate. So I'd like to ask what kind of flight envelopes you have seen and are these available from somewhere?
Anyway, turning comparisons I have seen are quite clear in this respect, when the P-38 opens maneuvering flaps at low altitude it's speed decrease soon to around 140-150mph IAS and at that speed it could turn tighter (I've seen comparisons with the Fw 190, P-47, P-51A and P-51D).
fats,
yeah, thread hi-jacking sucks...
gripen
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correct me if I am wrong, but are you suggesting that a P-51 with about 1,200 hp @ 25k and about 900 hp @ 30k had a large advantage over a P-38 with 3,200 hp and a much better power to weight ratio because the mustang could make use of a better prop and exaust gas?
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Originally posted by bolillo_loco:
correct me if I am wrong, but are you suggesting that a P-51 with about 1,200 hp @ 25k and about 900 hp @ 30k had a large advantage over a P-38 with 3,200 hp and a much better power to weight ratio because the mustang could make use of a better prop and exaust gas?
Even though I'm on the P-38 side of this argument, I'll be the very first to concede the P-51 had a decided advantage over the P-38 in prop efficiency. The Cutrtiss Electric prop was woefully inadequate, and Lockheed sought to address this by changing to the Hamilton Standard prop, which would have solved other problems also. So the P-38, while having an abundance of horsepower, an a great power to weight ratio, did not have a great power to thrust ratio. The P-51 had far less power, but a much better power to thrust ratio, so less power was wasted. To understand how bad the situation with props was on the P-38, you really should read "Whatever Happened to the P-38K" by Dr. Carlo Kopp at "Planes and Pilots of World War II", for the story on how big the difference the props made. Remember when you read it, that it was comparing the Curtiss Electric three blade trouble prone junk the USAAF supplied Lockheed, with the Hamilton Standard High Activity Hydromatic Paddle prop in a THREE blade version. The later FOUR blade version was even more efficient.
With the Hamilton Standard, the P-38 would have been even faster than it was, more fuel efficient, and held an even greater advantage in acceleration, over a wider range of speeds.
Exhaust thrust was non existent on the P-38, because the turbo would not tolerate the back pressure caused by the use of a hood to direct exhaust thrust. The P-51 gained some small advantage here by using exhaust thrust.
The big advantage in added thrust was the heated air exhausted from the radiator actually generated thrust at high speeds, because the radiator scoop on the P-51 was an excellent design for creating a ram effect. In fact, this design was so good, it appeared as a hood scoop on race cars in the late seventies. At high speed and under high power, the P-51 could actually generate about 15 MPH gain from the radiator exhaust.
I've been busy trying to get parts to upgrade my computer so I can fly instead of type, and my job has me tied up. So I have not been here looking in on this one, but I didn't "leave".
I talked to Warren Bodie twice in the last couple of days. Currently, he is extremely busy on a two volume history of the 8th AF, with a huge collection of color and black and white photographs. This is a huge undertaking, and he is desperately trying to get it done in time for the 60th anniversary of the 8th AF, in 2002. At the age of 78, that is all the effort he has time and energy for, so he has only sent me a few things in the mail about the 8th AF, and the P-38. I'll post them when they get here.
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bolillo_loco,
Well, a good starting point for comaprisons is a correct data set. With RAM the V-1650-3 did around 1200hp (or a bit more) at 30k and the V-1710-111/113 did around 1400-1550hp (53-57") at 30k. In the case of the P-51 we can also ad exhaust thrust which is around 200-300lbs. Then we should compare propeller efficiency and as Renegade Savage noted, propellers of the P-38 sucked (just look how speed starts to drop below critical altitude).
BTW why are you continously using worst possible or selfmade data for the P-51 (for example weights as seen earlier or these power values) in comparisons against the P-38?
gripen
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No grippen, I made a mistake on my part and assumed we were talking about the P-51D with the -7 engine, not the B model with the -3.
I still believe the -7 made about 900 hp at 30K and please remember I am going from complete memory since all my books were lost when I moved recently. split the 38 into half if you like. that gives a 38 1,600 hp and a weight of 8,800 lbs up to 28,700 ft (excluding fuel and oil burn) and a P-51D 10,200 lbs and 900 hp also at 30k and excluding fuel burn.
I am sorry I use the lowest data available for the mustang, it comes from americas hundred thousand. but not all the data in AHT is of a low nature. look at the charts for the pony, they use mustangs at 9,000, 9,200 etc take off weight so this data can not be considered the lowest around. the data for the P-38 in AHT is however the lowest performance data I personally have seen where it states a/c weights and hp used to achieve the data.
I have not seen all data out there so please remember this when I post :) nice chatting with you grippen
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bolillo_loco
Hm... I think I have made very very very clear that we are talking about the V-1650-3 powered P-51B (major variant in the ETO) and BTW the V-1650-7 did still around 1000hp (or a bit more) with RAM at 30k.
Anyway, finaly you are using near comparable (start) weights for the P-38 and P-51. Except that the P-51B was around 300lbs lighter and the P-38J around 99lbs heavier and the P-51 had a longer range with that loading (according to the AHT).
gripen
[ 12-14-2001: Message edited by: gripen ]
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Hi Gripen,
here are some numbers comparing the P-38J and the P-51B from the XF4U-4 comparison documented posted a while ago on this board.
Gross weight: P-38J 16415 bls, P-51B 9300 lbs
Fuel: P-38J 300 gallons, P-51B 180 gallons
Engine model: P-38J Allision V-1710-89/91, P-51B Packard V-1650-7
Manifold pressure: P-38J 60" Hg WEP, P-51B 67" Hg MIL
BHP sea level (1 engine): P-38J 1600 HP, P-51B 1510 HP
BHP rated altitude: P-38J 1600 HP, P-51B 1370 HP
Rated altitude: P-38J 25000 ft, P-51B 23300 ft
Vmax sealevel: P-38J 338 mph, P-51B 359 mph
Vmax 20000 ft: P-38J 402 mph, P-51B 419 mph
Vmax critical altitude: P-38J 415 mph, P-51B 450 mph
Critical altitude: P-38J 24800 ft, P-51B 29100 ft
Rate of climb sealevel: P-38J 3730 fpm, P-51B 3410 fpm
Rate of climb 20000 ft: P-38J 2910 fpm, P-51B 2430 fpm
Rate of climb critical altitude: P-38J 2750 fpm, P-51B 2400 fpm
Critical altitude: P-38J 22000 ft, P-51B 24800 ft
Time to climb to 20000 ft: P-38J 5.9 min, P-51B 6.6 min
Service ceiling: P-38J 42000 ft, P-51B 42000 ft
Radius of action: P-38J 450 miles, P-51B 550 miles
Radius of action is according to Navy specifications (cruise in at 15000 ft, 20 min combat at 15000 ft, cruise back at 1500 ft) and doesn't quite fit the 8th Air Force's mission profile :-)
From the performance graphs, it's obvious that the P-51B holds a clear speed advantage over the P-38J at any altitude. The P-38J in turn holds a climb rate advantage from sea level to 25000 ft, above 25000 ft climb rates of both aircraft are identical.
Regards,
Henning (HoHun)
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Hi again,
>Engine model: P-38J Allision V-1710-89/91, P-51B Packard V-1650-7
The document seems in error regarding the P-51B, the P-51B's engine actually should be a V-1650-3. Both speed and power curves seem to confirm that.
>Manifold pressure: P-38J 60" Hg WEP, P-51B 67" Hg MIL
>BHP sea level (1 engine): P-38J 1600 HP, P-51B 1510 HP
>BHP rated altitude: P-38J 1600 HP, P-51B 1370 HP
The document is a bit ambiguous here: The quoted powers are claimed to be for the Military Power setting of the V-1650-3, but 67" Hg should be War Emergency Power (at least it would be for the V-1650-7). The rated power graph repeats the quoted power settings. Unfortunately, it's not quite clear whether the quoted performance was achieved on MIL or WEP (I'd guess WEP), and whether the power graph is based on MIL or WEP (I'd guess MIL).
Regards,
Henning (HoHun)
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Hi Hilts,
>Exhaust thrust was non existent on the P-38, because the turbo would not tolerate the back pressure caused by the use of a hood to direct exhaust thrust. The P-51 gained some small advantage here by using exhaust thrust.
The BMW801D, which at 30000 ft had a similar power output as the V-1650-3, would deliver about 140 HP worth of exhaust thrust at a climb speed of 160 mph IAS. At the P-51B's top speed, it would be roughly 240 HP.
This is not "some small advantage", but a serious 20% power increase.
Regards,
Henning (HoHun)
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Here (http://naca.larc.nasa.gov/reports/1946/naca-tn-1044/index.cgi?page0028.gif) is a little graph from a (http://naca.larc.nasa.gov/reports/1946/naca-tn-1044/) NACA document. This explains a bit those CLmax things I described earlier. Please note that the P-38F weighed 15800lbs and the P-51B 9300lbs on the tests.
gripen
PS: This thread is becoming huge...
[ 12-15-2001: Message edited by: gripen ]
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Hi grippen, turn the page of your copy of AHT to the P-51, you will note that the D model has fallen to 1,200 hp at about 25,000 ft and that at 30,000ft it has fallen to 900hp. I do not remember the hp figures for the -3 engine, but I do remember it has a definite edge above 20,000ft
I do not doubt that at high speeds that the P-51 has a better CL max. however of what importance is this when the mustang does not have the hp to support this.
10,200 lbs and 900 hp vs 17,600 and 3,200 hp does not look like a good power to weight compairison. the 1,720 hp the -7 made falls off to below 1,600 hp at any altitude above 6,250 ft. those hp figures mean that at altitude the mustang has about 11 lbs per hp vs the 38 which is around 5.5 or half the loading. that is also in americas hundred thousand, near the back in the plane compairisons.
while in the book look at the speed for a P-51B that has taken off at full weight and is not a stripped down version. the TAS is 425-430 mph. the 450 mph in the test states all the improvements and special care taken to make the P-51B much faster than a common front line fighter. special sanding of wings and care to improve the fit of cowlings, special high octain fuel, rear tank removed, etc.
the 443 is a plane of similar care and no rear fuselage tank and the 440 is one with the tank in place, but empty on take off. that is also in americas hundred thousand.
it has been stated earlier that the P-38L's max speed begins to fall off above its critical altitude. this is just more misinformation. look at the AH cart for the P-38L and then look at the AHT chart for the P-38J. they are exactly the same. this is because the data floating around in every book is from one test and that is of a P-38J at a take off weight of 17,600 lbs so it is one with the leading edge tanks. and critical altitude is 26,400ft because it is a pre J-25-LO and does not have the engine/turbo improvements and that matches the curve of both AH and AHT. it is not due to propellers, but that the actual critical altitude is 26,400 ft. I believe that is also in AHT.
The high performance 3,500 fpm climb and 440 mph tas of the mustang is always taken from specialy prepaired mustangs which do not represent front line fighters taking off for a long mission full of fuel with scuffed and or dull paint. while the 38s in the tests always appear to be in poor condition.
since the P-51B is mentioned a lot in this thread please take note that the critical mach number is .75. the B model and early D models all had fabric covered elevators. this caused the plane to buffet uncontrollably. so the plane with fabric covered surfaces cannot be safe above mach .75 and the pilots manual says to quickly reduce power and ride it out until it reaches denser air closer to sea level. it states that the a/c will begin to buffet and porpoise and this condition is very dangerous.
the 4,000 + fpm climbs for the P-51 have to be from some very special mustangs. considering this is better than spitfire perfromance. any altitude above 6,250 ft the spit IX and 51 have about the same hp and somebody stated that a 10,200lb P-51 is suppose to climb with a spitfire that weighs 3,000lbs less. how can it do this? high speed climbs are very shallow and do not approach 3,000fpm. the pilots manual states best climb speeds for the mustang is around 160 mph IAS.
I purposely state the lowest data available because it looks like it is taken from a common mustang which does not have special improvements done. I do this because the 414 mph and 3,800 fpm is from a common P-38J model with 410 gal fuel capacity internal and is also the lowest data available for this plane type.
[ 12-15-2001: Message edited by: bolillo_loco ]
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also note in the test that hohun posted how the 38J has a weight of 16,400lbs yet cannot match the climb of 3,800 fpm of a 38 at 17,600 lbs in americas hundred thousand nor the same identical chart at aces high. look in the pilots manual for a P-38H. the H at 16,800lbs climbs at 3,500 fpm under military power (1,420hp) this is a fair compairison because for climbing purposes below 10,000ft the performance of an early J model and a H model are identical providing the J model does not have the leading edge tanks. what that test says to me is that a plane 800 lbs lighter with 400 hp more can only climb 200 fpm faster.
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I began looking at the naca report and again it looks like a case of special preparation to the mustang while the 38 is a typical ragged out version.
"The P-51B and the YP-80A airplanes had very carefully filled, waxed, and polished surfaces. The other airplanes were painted with standard camouflage paint. Of the six airplanes tested, the P-38F and P-39N airplanes had the roughest finish and the most openings in the wings."
http://naca.larc.nasa.gov/reports/1946/naca-tn-1044/index.cgi?page0004.gif (http://naca.larc.nasa.gov/reports/1946/naca-tn-1044/index.cgi?page0004.gif)
I also stated earlier that wing surface condtion is critical and it looks like the data presented is from two different types of tests. the one the 38 was subjected to will lead to lower results than the one the mustang was subjected to so the chart is very decieving making the mustang look like it has better CL max numbers at all speeds when it is two different tests ploted on the same chart.
[ 12-15-2001: Message edited by: bolillo_loco ]
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Hi Bolillo_loco,
>I do not doubt that at high speeds that the P-51 has a better CL max. however of what importance is this when the mustang does not have the hp to support this.
At 30000 ft, turn radii are wide, and sustained turns are slow - in the region of 60 s for a full circle. Serious combat up there involves losing energy, and the Clmax advantage of the P-51 means that it's better at instantaneous turns.
Remember that kinetic energy increases with the square of true air speed - and while indicated air speeds are quite low up high, true air speeds provide the aircraft with quite a lot of energy to burn in instantaneous turns.
Additionally, the HP number doesn't tell the entire story as the Merlin engine adds a good amount of exhaust thrust to the propeller thrust which the turbo-supercharged Allison does not.
>the 443 is a plane of similar care and no rear fuselage tank and the 440 is one with the tank in place, but empty on take off. that is also in americas hundred thousand.
"P-51 Mustang" by William Grant quotes a 440 mph speed for the P-51B, so I'd say 450 is in the ballpark. Even if you subtranct 20 mph from the P-51B's speed at all altitudes, the graph shows it'll still be faster than the P-38J except around the supercharger gear change altitude (22500 ft). The P-38J at best holds a 10 mph advantage at that altitude.
With regard to the empty rear fuselage tank: The combat radius of the P-51B as listed in the document I quoted still exceeds that of the P-38J listed in the same document, so I'd call it a fair comparison.
Regards,
Henning (HoHun)
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I am not talking about ranges, the mustang for a fair compairison must take off in combat trim with out sanded and filled and waxed wings with full fuel on board. this means the mustang does 425-430 mph. it is in AHT I do not make this up. 440 and 450 mph speeds are once again specially prepaired mustangs with sanded and filled wings and highly waxed taking off 1,200+ lbs light. that is why they are so fast and climb in excess of 3,000fpm.
the mustang has 900 hp at 30K vs 3,100 hp for the lightning. I am to believe exaust gas and a propeller will make it turn better because this adds a lot of power to a under powered plane? the propeller does not improve high speed, it is to make the plane climb better and accelerate better at low speeds. both the P-47 and P-51 saw benifit from this propeller. it was added to improve poor rate of climb and acceleration, look at the speeds of the P-47 before and after. no significant gain in speed, but climb went up and that is what the prop was made to do.
if you are to use high data for the mustang then high data for the 38 should be used. warren bodie states 1,725hp for the 38L and 440 tas top speed and climb in excess of 4,000 fpm
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Hi Bolillo_loco,
>the 450 mph in the test states all the improvements and special care taken to make the P-51B much faster than a common front line fighter. special sanding of wings and care to improve the fit of cowlings, special high octain fuel, rear tank removed, etc.
When the US Navy tested the P-51B against different models of the F4U, their Mustang achieved 358 mph at sea level and 450 mph at 29200 ft at a weight of 9423 lbs.
Their comment on the condition:
"The P-51B, as flown, was in a drag condition slightly superior over that of a standard production airplane, by reason of minor changes in the external radio installation and smooth sanding of the wing."
For comparison, one of the Corsairs had received much more attention (wing fold hinge line sealed and faired, tail hook removed, cowling precisely fitted, faired and smoothed skin), and the total speed gain was estimated to be about 8 mph at upper critical altitude. The benefit the P-51B experienced from the skin smoothing alone certainly was less than even these 8 mph.
But anyway: The fighter squadrons of the 8th Air Force often not only smoothed and sanded their aircraft, but actually polished them. The P-51 in operational condition in this case obviously were superior to standard production aircraft, too.
>the one the 38 was subjected to will lead to lower results than the one the mustang was subjected to so the chart is very decieving making the mustang look like it has better CL max numbers at all speeds when it is two different tests ploted on the same chart.
You might have noticed that the report relied on a number of independend tests (including wing tunnel tests with models not affected by surface roughness problems) to confirm the findings, and the drop of the P-38's maximum lift coefficient with Mach number was validated that way. Perhaps a carefully maintained P-38 would lose slightly less than the quoted 40% of its lift at medium speeds in high-altitude combat, but there can be no doubt it lost significant amounts of lift.
Just look the the graph for the F6F which was in a better condition than the P-38F - it lost lift just the same.
Regards,
Henning (HoHun)
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Hi Bolillo_loco,
>I am not talking about ranges, the mustang for a fair compairison must take off in combat trim with out sanded and filled and waxed wings with full fuel on board.
For the surface condition, see above.
With regard to the rear fuselage tank, there's a good reason it's usually not included in performance figures: It was intended to be emptied before entering combat. When the P-51 dropped its tanks in combat operations, it was down to the fuel in the wing tanks. When the P-38 dropped its tanks in combat, it was down to full internal fuel. These are the two matching configurations that you have to compare for a meaningful performance assessment.
>if you are to use high data for the mustang then high data for the 38 should be used.
I quoted the above document since it provided detailed set of matching figures on both types that are of interest to us. The combination of P-38J and P-51B data sets in this report was not selected by me, but by the authors of the original report.
When I compared the P-51B data to the most detailed report I've come across, the Navy comparison to the F4U (that certainly is free of any pro-Mustang bias!), the P-51B's top speeds were confirmed with good accuracy.
>warren bodie states 1,725hp for the 38L and 440 tas top speed and climb in excess of 4,000 fpm
As discussed previously, Warren Bodie's figures apparently rely on the 64" Hg power settings that were never cleared for operational use by the USAAF. The US Navy figures for the P-51B rely on the 67" Hg power setting that apparently was the accepted standard power.
Regards,
Henning (HoHun)
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it still falls down to mustangs with special attention payed to them while the 38 that is tested are always ragged out.
If you have americas hundred thousand page thru to the charts inside for the mustang and look at what the P-51B did for top speed when it took off with the rear tank inplace and full and was not a specialy trated mustang. it did 425 to 430 mph max this is much slower than the "specialy treated mustangs that do 440+ mph" so this is not representative of common 8th airforce pratice. also note the 150 oct. fuel used for these tests.
since it was pointed out that a mustang must burn its 85 gallons of internal fuel before it goes to drop tanks, what happens to the mustangs range when it must drop the external tanks that are still full due to enemy action? its range suffers, also the added drag of the tanks has to also cut down on the range because it had to carry the tanks much farther because it did not burn them as soon as it took off.
I only see it as fair that if the P-51 mustang is to recieve the highest rate of climb and speed figures then it sould be so for all other planes, be they russian, german, japanese, and or american.
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bolillo_loco,
Well, there several errors on engine ratings in the AHT. Forexample that graph 37 for the V-1650-7 is without RAM as text states but values for the V-1650-3 are with RAM (there is same error in the next page on table 46. With RAM the V-1650-7 did at least that what I stated, check manual if you don't believe. Also in the case of the P-38 there is errors too; ratings for the P-38H wrong (rammed WER should be 10k and so on) and again there is rammed and unrammed ratings mixed for the P-38J and L (unrammed WER should be 25800ft and rammed 28700ft for both, check manual again). Also it should be noted that limiting factor for the B-33 turbo (same for the J and L) is overspeed 26400rpm for WER, not regulator or what ever.
About Clmax advantage of the P-51 it should be noted that at 30k mach 0.3 less than 150mph IAS (assuming standard conditions) so the P-51 tend to be better all over speed range. I wonder from where you have got a idea that the P-51B or P-51D did not have the power to use this advantage? As noted earlier even with the V-1650-7 the P-51 had power at 30k. BTW typical combat loads for the P-51B or D are around 9000-9800lbs and around 17000lbs for the P-38J, I wonder how many times I should point this out?
About test results for the P-38 it should be noted that I have seen three separate and different datasets for various P-38J and L models and decrease of the speed below critical altitude exists in every one of them. AFAIK the smooth finish in the wings was a standard for the P-51, even planes with metal finish had actually wings painted with metal color (see pictures, you can actually see it). And about tests (A&AEE, RAE, NACA, USAF), generally you should prove that these were somehow unfair otherwise you are just wasting bandwidth and blaming people who just tried to make their best for their country. BTW I have also additional wind tunnel data which supports those Clmax values in that NACA report. And surface finish does not change the fact that aerodynamics of the P-38 sucked at high altitude and high speed.
About dive characters of the P-51 it should be noted that overall the P-51B was better than P-51D because it had better directional stability. Fabric covered elevators were not a big problem if the plane was trimmed nose heavy (actually Borsodi made his tests with a early P-51D which had fabric covered elevators). And later modified planes actually had critical mach number around 0.8 (metal covered elevators and stabilizer incidence change).
I believe there is no reason to discuss about those 1725hp claims until some one comes out with verifyable and more accurate data, BTW use of the +25lbs can be verified in the case of the Mustang.
gripen
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Hi Bolillo_loco,
>it still falls down to mustangs with special attention payed to them while the 38 that is tested are always ragged out.
The Mustang tested by the US Navy was in poorer condition than operational 8th Air Force Mustangs.
I have no indication that the P-38J tested for comparison with the XF4U-4 was ragged out.
With regard to lift coefficient Mach numbers, you missed that the F6F which was not ragged out was almost as badly affected as the P-38. I'd also like to point out that the P-63A which did not receive the same surface treatment as the P-51 or the YP-80 but had a laminar-flow airfoil displayed the same kind of behavior as the other laminar wing fighters, and the same superiority to non-laminar fighters too.
>it did 425 to 430 mph max this is much slower than the "specialy treated mustangs that do 440+ mph" so this is not representative of common 8th airforce pratice.
Well, the Navy had no reason to try and make the P-51B look better than their F4U - in fact, if there's a bias in the report, it's pro-Corsair. Still, their P-51B achieved 450 mph on standard power settings.
>also note the 150 oct. fuel used for these tests.
Since the 8th Air Force operationally and on a large scale used grade 150 fuel with the P-51 in the summer and autumn of 1944, and from February to April 1945, there's nothing wrong with it. The 67" Hg WEP used to achieve 450 mph is a setting for grade 130 fuel, though, so it's actually a conservative figure.
>since it was pointed out that a mustang must burn its 85 gallons of internal fuel before it goes to drop tanks, what happens to the mustangs range when it must drop the external tanks that are still full due to enemy action?
Even with fuselage tank empty, the P-51B's range is longer than that quoted for the P-38J on full internal fuel by the same report.
>its range suffers, also the added drag of the tanks has to also cut down on the range because it had to carry the tanks much farther because it did not burn them as soon as it took off.
Relying on the Flight Operation Charts in AAF Manual 51-127-5, the difference in range yielded by 85 gallons fuel burned with 2 x 110 gallons long range tanks under the wings and the same amount of fuel burned with empty wing racks amounts to 35 statue miles based on a fast cruise at 25000 ft at 46" Hg.
Regards,
Henning (HoHun)
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Hi grippen, I have noticed errors you speak of in AHT and even pilots manuals and you are correct. I remember the P-38H, J, and L have incorrect data for critical altitude, I think it is the H model and you are correct in saying that wep (1,600hp for the H) at 26,400 ft is incorrect. that was the theory, but the pilots manual states 10,000ft is max and even in the pilots manual for the 38H it states military power is possible at 26,400 ft. from what I have read the usable power is probably 1,240hp at that altitude as stated in warren bodies book if I am not mistaken.
correct me if I am wrong on the weights for the P-38J/L and P-51D. full internal fuel and ammo and oil with external hard points, but not external stores with a pilot.
as stated in americas hundred thousand
P-51D 10,208lbs
P-38J/L 17,699lbs
this does not include any fuel burn for start up and take off allowance.
with the link you posted grippen for Cl max, I just wanted to point out it clearly states the P-51's wing was sanded and filled and waxed and that the 38F had dull paint and suface condition was rough (the poorest of the 7 types tested) and had holes in it.
I feel this is not a fair compairison. I am not however saying that the Cl max for a 38 is higher than a P-51 at speeds above mach .6 tas. just that I am sure that the 38 would have higher numbers than shown if it had the special wing work done. this is very important in how the airflow sticks to the wing as well as the leading edge is also critically important.
you were also very correct in stating this thread is very long :)
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bolillo_loco,
The limiting factor for WER (60", 7k, 10k with RAM) in the case of the P-38H is intercooling capacity with both possible turbo versions (B13 and B-33). But for MIL (54") critical altitude for the P-38H depends on turbo being around 22k with RAM for the B-13 and between 23-25k depending on RAM for B-33 (manual I have claims ratings exactly just for the B-33, 24900ft with RAM and 22k without RAM). But it should be noted that after early problems with WER most P-38Hs were limited to 54" WER (see Whitney: Vee's for Victory).
Those weights you claimed can be confirmed from the AHT and actually I have claimed them too. But we are interested about typical combat weights which are those I claimed above and relevant comparison for the ETO is P-51B vs P-38J. BTW your earlier claim 8lbs fuel burn for the P-51D when it climbs to the 30k...
About finish of the P-51B it should be noted that smooth finish was a standard for wing. The P-38F had also standard finish and some problems with surface but it was also around 1200lbs lighter than the P-38J at typical combat weight while the P-51B weighed about that P-51B used to in combat. I see no reason to believe that results are not valid nor that test favors P-51B. And as noted earlier the P-38J needed higher Clmax for same turning performance as the P-51, so we can see that the P-51 has clear advantage at hole speed range at high altitude. BTW wind tunnel tests also support results.
Well, IMHO the main reason for long thread appears to be that someone can't accept documented tests, weights and engine ratings.
gripen
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Isn't this thread dead yet? let it die , jeez 170+ posts.
Start another for Cod's sake it takes over a min to load even with DSL
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Hi Bolillo_loco,
>correct me if I am wrong on the weights for the P-38J/L and P-51D. full internal fuel and ammo and oil with external hard points, but not external stores with a pilot.
>as stated in americas hundred thousand
>P-51D 10,208lbs
>P-38J/L 17,699lbs
The P-38J as tested for comparison with the XF4U-4 weighed 16415 lbs with 300 gallons of fuel.
The P-51B as tested for comparison with the XF4U-4 weighed 9300 lbs with 180 gallons of fuel.
These are the operational meaningful numbers to compare.
Since you're insisting on a full internal fuel load: The P-51B with 85 gallons of internal fuel would weigh 9840 lbs. The P-51D in similar conditions would weigh 10090 lbs.
Be careful what you do with these numbers though: The internal tank was only full when the Mustang was still carrying its droptanks, so operationally, the weight of the fuel in the fuselage tank was meaningless. If you use these numbers as basis for a comparison of combat capabilities, I'll have to assume you're merely interested to make the P-38 look better.
>with the link you posted grippen for Cl max, I just wanted to point out it clearly states the P-51's wing was sanded and filled and waxed and that the 38F had dull paint and suface condition was rough (the poorest of the 7 types tested) and had holes in it.
>I feel this is not a fair compairison. I am not however saying that the Cl max for a 38 is higher than a P-51 at speeds above mach .6 tas.
The results of the NACA report were carefully double-checked wind tunnel tests of aircraft models in the Ames and the Langley 16 ft wind tunnels which confirmed the findings. The Ames 1 by 3.5 ft wind tunnel tests of wing sections however matched the other test results closely except for those for the P-38F. This confirms that the P-38 not only had the same wing section compressiblity problem as the other fighters with conventional airfoils, but that the rest of the airframe contributed to the compressiblity problem as well.
Here's the comparison of the Mach-induced drop of the P-38F's and the P-51B's lift capabilities:
Mach - IAS - P-38F - P-51B
0.3 - 138 mph - 100% - 100%
0.4 - 184 mph - 88% - 93%
0.5 - 230 mph - 74% - 92%
0.6 - 276 mph - 58% - 94%
In other words, the P-38F loses significant amounts of lift through the entire speed range, while the P-51B loses only a very small amount.
The NACA report leaves no room for the assumption that the observed Clmax drop is the result of poor surface condition.
Have a look at the numbers for the F6F (which uses a similar wing to the P-38F but is not affected by its airframe-induced compressiblity problems) and the P-63A which had a similar surface condition (data for 25000 ft):
Mach - IAS - F6F - P-63A
0.4 - 194 mph - 100% - 100%
0.5 - 243 mph - 82% - 96%
0.6 - 291 mph - 63% - 109%
>I am not however saying that the Cl max for a 38 is higher than a P-51 at speeds above mach .6 tas.
The NACA report clearly shows that at high altitude the maximum lift coefficient of the P-38 drops quickly with increasing speed - starting right at the stall. This is not a phenomenon limited to high speeds, it affects the entire speed range.
Regards,
Henning (HoHun)
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thanks for the explanation hohun and grippen
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I have to go now, my mummy is calling for me :(