Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: BBGunn on January 25, 2001, 05:18:00 PM
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In a small test I dove the AH P38 at 1/2 fuel, no bombs or rockets, trimmed level, IAS 225mph, 40" manifold and prop pitch at max from 15,000ft: three times with dive flaps and three times without and I could not tell any difference. Pilot comments from Martin Caidins book P38 Fork-tailed Devil indicate that the P38L should be safe to dive from 15,000ft especially with dive flaps deployed and was able to chase split S'ers. In AH the ship accelerates rapidly and when passed 450mph the elevator response quits and up trim may get you out of the dive if there is enough alt left. IMO the flaps in AH should have more of an effect on speed and turn. The 38 would also not likely experience any compressablilty at low altitudes like 15K and below.
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ive done some reserch of my own, or you could call it lookin for info, anyway as some of you may know Evergreen (that cargo company) has a musiem, one of the aircraft on dispay the P38-L sound familer, well on the info sheet it says its maxmum speed is 415 ias, and they also have a 109-g10, its max. speed is 428 ias and i dont think it gave a alt that the speeds would be acheved at.
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(http://www.user.shentel.net/vonz/jato.JPG)
[This message has been edited by jato757 (edited 01-25-2001).]
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I've done some research of my own, or you could call it looking for info, anyway as some of you may know Evergreen (that cargo company) has a museum, one of the aircraft on display the P38-L sound familiar, well on the info sheet it says its maximum speed is 415 ias, and they also have a 109-g10, its max. speed is 428 ias and I don't think it gave a alt that the speeds would be achieved at.
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(http://www.user.shentel.net/vonz/jato.JPG)
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The dive flaps installed a later P-38s did several things.
1) They prevented the scenter of lift from moving towards the trailing edge of the wing, thus inducing the dreaded 'tuck under'. This could cause the aircraft to do an outside loop, with G levels exceeding 8 gs. Like the wing flaps, the dive flaps induced some pitch-up.
2) The flaps added drag, which reduced both dive acceleration, and ultimately, peak velocity.
The P-38 would pull out of a high Mach dive at a steady 3 gs, hands-off. Having downloaded the AH software, I noticed that the maximum speed for the P-38 is limited to 450 mph. This is accurate for if at 25,000 feet. However, the P-38 is placarded for considerably higher at lower levels. I have duplicated the redline airspeed chart from the Pilot Training Manual and have posted it here for everyone to use.
Perhaps, the designers will consider this data the next time they look at thier P-38L modeling.
[img]http://home.att.net/~ww2aviation/RedLine.html [/img
My regards,
Widewing
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Let me try posting the chart again.
[img]http://home.att.net/~ww2aviation/RedLine.JPG [/img
My regards,
Widewing
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Maybe someone could explain what I'm doing incorrectly....
Or, perhaps someone would spare me further humiliation and post the &%$*#%&%@$!&% chart for me. :-(
My regards,
Widewing
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Originally posted by Widewing:
Maybe someone could explain what I'm doing incorrectly....
Or, perhaps someone would spare me further humiliation and post the &%$*#%&%@$!&% chart for me. :-(
My regards,
Widewing
My pleasure... The syntax has to be 100% and is case sensitive.
(http://home.att.net/~ww2aviation/RedLine.JPG)
Leon "Badboy" Smith
[This message has been edited by Badboy (edited 01-25-2001).]
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Widewing,
Here you go. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
(http://home.att.net/~ww2aviation/RedLine.JPG)
BTW, you had a space between the "JPG" and the "[". Thats why it wasn't working.
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We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother
Sisu
-Karnak
[This message has been edited by Karnak (edited 01-25-2001).]
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(http://home.att.net/~ww2aviation/RedLine.JPG)
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Posted by Karnak:
"Widewing, Here you go. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)"
"BTW, you had a space between the "JPG" and the "[". Thats why it wasn't working."
Thank you, and thank's to BADBOY too. I figured it out while you guys were posting the chart. So, now we have three copies!
Again, thanks for your help.
Widewing
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I see three charts above me, I find it hard not to post a 4th one. hehehe. ok wide wing. I have seen 3 different placard type dive charts from the usaaf. I am going to assume that the 1 that says 420 mph ias is an early chart, the one that says 440 was a chart around 1945 and the chart you posted is a post war dive chart. or are the three different due to errors in airspeed indicators and the usaaf or lockheed changing them or calibrating them differently? can somebody explain the 3 different charts? I have seen the above one in its official form.
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sorry I mean the speed after the ias one for 10,000ft. some have 440, 460, and 480. what gives? the first number is always the same while the second changes.
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The early charts may not have been averaged for all climates.
The temperature aloft will vary according to the temperature as sea level. Using the basic calculation for a Standard Air Column, we find that under Standard conditions (Barametric pressure of 29.92 in/Hg @ 59 degrees F), the temperature of the air will decrease by 3.5 degrees per 1,000 ft. increase in altitude.
I do know that the Manual for the P-38L says of the redline chart:
Note: This chart has been designed for standard atmospheric temperature and pressure and the TAS has been corrected for average pitot location error.
I should also mention that early P-38s had the pitot located under the nose, with later models having it under the left wing. During the course of the war, the pitot tube changed slightly in length and the static system was revised several times. In all likelihood, this will account for the differences.
Other than the above, I cannot offer a better explanation.
My regards,
Widewing
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ok and if I am reading the dive limit chart right for the P-38 in the pilots manual, the 420 mph ias is for a 3g pull out. cause it looks like it goes down to 390 mph ias for 6gs. and lastly how does the CAS and IAS differ here and throw off the speed?
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Originally posted by bolillo_loco:
ok and if I am reading the dive limit chart right for the P-38 in the pilots manual, the 420 mph ias is for a 3g pull out. cause it looks like it goes down to 390 mph ias for 6gs. and lastly how does the CAS and IAS differ here and throw off the speed?
Aircraft of that era did not have the most accurate technology, especially in measuring airspeed. Several things could distort the normal relationship between indicated airspeed and true airspeed. High angles of attack is one. An aeronautical engineer could answer your question better than I.
Another oddity occurs during high speed dives. The pressure change in the static system can lag well behind the airplane. In other words, in a high speed dive, possibly at rates above 35,000 ft/min, the pressure in the system cannot increase as fast as the aircraft descends. The altimeter may be at 25,000 ft, while the aircraft is passing 20,000 feet. This leads to the pilot believing that his speed is greater than it actually is. Lockheed began installing a simple machmeter in their test aircraft in mid 1944. This eventually worked into the production line with later run P-38Ls. Unlike a static pressure system, the machmeter was apparently not effected by rapid barametric pressure changes.
My regards,
Widewing
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I KNEW my baby could fly faster and turn better.
Keep the data coming Widewing, thanks for your efforts! You too Badboy! Lets get the P-38 right in AH (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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It'll still just be a target... a very BIG target (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
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Vermillion
**MOL**, Men of Leisure
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Thanks for taking time to post the charts: I took a second look at Martin Caidins book and there is one reference to an IAS of 445 as being the max safe speed at 36,000 (mach number .675). Thats fairly close to the chart. Since the speed of sound is about 765mph near sea level at 60degrees F and is approx 105mph slower at 36,000 feet this makes sense. In a nutshell I believe that HiTech should consider giving the P38L another 50mph of speed before it looses elevator control at 15-16K and below. That would give it about 500mph before the elevator control gets weak. I think that would be good in AH. As far as the rate of turn increase when dive flaps are deployed-I have no idea other than that it was mentioned by American pilots who fought against Me109's and FW190's to increase turn rate for both offensive and defensive combat.
[This message has been edited by BBGunn (edited 01-26-2001).]
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I found a minute to search through my Lockheed data and turned this up.
(http://www.netcomuk.co.uk/~badboy/PDF/P-38-Dive2.jpg)
Chart was signed and dated April 1942. I have one other dated 1940, but it was estimated and quite optimistic.
Leon "Badboy" Smith
[This message has been edited by Badboy (edited 01-27-2001).]
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The 1940 dive curves, while only estimates, show a curve for anticipated compression effects. I find that interesting because it shows that they were considering the problem quite early on, but that they were actually quite far off the mark. Just saying.
Leon "Badboy" Smith
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Historical note: I think it may have been Kelly Johnson at Lockheed who predicted compressibility sensitivity with the P38 early on.
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<punt> for you know who
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Just because I'm an idiot with a dream...
xBAT
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I love you westy! you a true pal.
Oh..he meant HT.. of course...
Ht.. git on it! (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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Forgive my foolsome ignorance, but I fail to comprehend why the P-38 is just a target in the arena. I mean, we don't freeze our butts off in the cockpit because of ill fitting gun cowlings. We don't need to worry about engine problems, control complexity, or anything else that prevented it from going down in history as a truly excellent plane.
So shouldn't the P-38L be a damned competent airplane in AH? Seems to me like a twin engined paper airplane that broadcasts an "Attack me, I'm in a P-38" to everyone in the sector...
P-38s were anything but paper airplanes.
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Okies... I'm throwing this stuff up tp bring attention to a percieved FM problem. I wish to remain civil and to give HTC the chance to respond? I've heard that several FM's are unfinished... is this what the 38 is?
xBAT
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Well guys, I can tell you this frommy experiences ctually working on a 38. The dive flap, is actually not a flap, but instead is actually a spoiler. This spoiler, disrupts airflow, increases drag, Tremendously, and should have an IMMEDIATE effect on slowing the aircraft. Yet, even though I have worked on it, I do know that actual flight info is golden, so I do ask 38 pilots, when you can actually find one, about that system, and they generally say that it kept the aircraft under control.
So, who knows, to me, it seems that the effectiveness of the flap is under modeled.
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Actually Bodhi, I think it is non-existent. I trim the elev full up to pull out of a compression, when compressed the dive flaps do zilch, when initiating a power dive, they do zilch.
The do turn on a yellow light in the cockpit though... (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
I have a scanned copy of some pages of HANGAR FLYING, a magazine issued to P-38 pilots that was used to give the pilots more info, directly from the test pilots trying out new stuff in the US as well as stuff from vet pilots. 6 pages are dedicated to dive flaps and they say that if the dive flaps were extended BEFORE the dive, you could keep the aircraft under control when you hit compression (under control meaning without the "tuck under" and without a "nose up" effect mentioned next-> ) , and if they were deployed AFTER the dive, when at or when near compression, the flaps would then produce an inmediate nose up lift that would pull the 38 by itself...the test pilot in the magazine even said that it would pull a neat loop all by itself if you let it.
Another thing that amazes me is the accel..or drag..or prop drag or whatchamacallit that makes a 25% fuel 38, at 10k and 100mph dive with full military power and gain 400mph (watching the white tick marker, not the red real speed one) at 5k, then trying it again at 10k, starting with 100mph.. turn engine OFF, wait for props to stop..diving same angle.. and get to 360 mph at 5k. So what, the engine only pulls 40 mph in 5k of diving? I would love if someone else tried this, im astonished.
HT, I think you should look at these P-38 magazines, i'll try and get as many as possible for ya if ye want them, a fellow AH'r was a lucky tard and got them on E-bay (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif) . Where can I submit them (5megs what I have now)?
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OK OK Badboy I supplied that 38 info to ya man.. Tfs#1 here
badz it been a while man.. ( i think)i hoped that stuff would help ya outr some time :) I got all kinds of stuff on the 38.. old airpower mags fight manuals stuff from lockheed from my dad and uncles etc. etc. :)
I'm gonna give ya a link to look up something thast migh help this some more..
http://www.p-38online.com/cmprs.html
anyway i'm gonna try to post some stuff on turnin the 38 and some other tactics.. Badz should have that stuff to its out of a air power mag.
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Dont want to know why a thread a year old came up, but any info on the 38 , not matter how old, is always welcome :)
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Oh so my 2 cents worthg anit worth nothin :) hehehehhe Just wanted to help out with this.
CW