Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: 1K3 on April 25, 2007, 01:52:17 PM
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Which of these planes can reach the deck faster at a 45 degree angle dive?
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Without looking it up I'd bet it is the P-47.
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Interestingly the Fw 190 has a higher critical Mach number than the P-47, so if both aircraft dived steeply enough to reach such speed the Fw 190 would pull away from the P-47. I don’t know what angle the dive would be however.
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i think the p47 would win.
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I need numbers!
(I'm @ school right now, can't do this Fw 190 vs P-47 test)
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Interestingly the Fw 190 has a higher critical Mach number than the P-47, so if both aircraft dived steeply enough to reach such speed the Fw 190 would pull away from the P-47. I don’t know what angle the dive would be however.
The dive restriction on the P-47 is much higher than that of the FW190A series. The P-47 is restriction is over 500MPH at 10K while the FW190 is limited to 466MPH (Luftwaffe restriction listed in cockpit).
The P-47 will out dive a Mustang. Check out Neil and Mike's webpage for comparitive dive performance here
Dive performance (http://www.wwiiaircraftperformance.org/wade-dive.jpg)
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now how about in-game...
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In the game my money is on the 190.
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Hi,
some weeks ago i made such tests(in a very simply way).
I took a 190A8 and a P47D-25, climbed to 25000ft(here the A8 have a wep climb of around 1800ft/min, the P47 around 2000ft/min w/o wep and around 2900ft/min with wep). Then i accelerated to 200mph and started a dive. While looking to the right sight initially the horizon fog started in the upper left corner of my screens(dont know exact what dive angle this was, no WEP but full throttle), now i enabled the "flight autopilot angle mode", what keeps the current flight angle constant(as long as the flight physics allow it).
The 190 accelerated rather fast under hard bufferings to 600mph, here the trim wasnt enough to keep the dive angle, so the plane raised slowly the nose, and after around 45sec, in around 3k alt, the plane was in a level flight starting a slow climb.
The P47D-25 had a suprising slow acceleration, the buffering did start more early and it never did reach 600mph, but it also leveled out alone in around 5k alt after around 55sec.
Since the P47D have a MUCH better climb in 25k alt, it also should have a much faster dive acceleration up there as result it should dive much faster.
But here, imho, the wrong FW190A8 FM show up.
The FW190A8 imho have to few drag(specialy parasite drag), but it miss power. As result the plane is realistic fast, have a realistic climb(both rather on the lower end of the scale) but on the other side it dive to good and it bleed to much energy while turning with full power.
But of course it could also be the other way around: Then the P47 would be to powerfull and would have to much drag, resulting in a realistic Vmax, but a to bad dive.
I often fly a FW190A8 and without engine(no power) it need ages to slow this plane down, the Sp16 for example decelerate MUCH faster, if both planes have the trottle on zero.
BUT, if both planes turn with full power, the 190A8 decelerate much faster, althought it have some hundret HP more power(it looks like we have the 2050HP 190A8).
I see a big discrepancy here!! Also while a full power highspeed upzoom the FW190A8 is one of the badest planes in game, although the powerload and inertia are rather good(at least in low level). Even the 109F4 own the FW190A8 in a highspeed upzoom, although the FW190A8 has a better powerload and keep MUCH more inertia.
My conclusion:
The 190´s need more drag, but more power in relation to the other planes.
Greetings,
Knegel
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Calling Widewing to the front Widewing please ......:D
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well, the way it *should* be is thus...
the 190 may have a higher critical mach number, but no plane in the ETO short of the -38 could match the Jug's initial dive acceleration. Several 56th pilots informed me that the aircraft would hit compression within seconds after unloading it and firewalling the throttle.
Best way to dive- unload. 0G's. No match angles, no autopilot tricks. Keep the acceleratometer at 0, then see how quick and how fast you go. The 190 may win the top speed race, but the -47 will get to it's top speed long before the 190 will.
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25,000 feet? I'm too scared of spacemonkeys to go that high... :O
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Originally posted by Rebel
well, the way it *should* be is thus...
the 190 may have a higher critical mach number, but no plane in the ETO short of the -38 could match the Jug's initial dive acceleration. Several 56th pilots informed me that the aircraft would hit compression within seconds after unloading it and firewalling the throttle.
Best way to dive- unload. 0G's. No match angles, no autopilot tricks. Keep the acceleratometer at 0, then see how quick and how fast you go. The 190 may win the top speed race, but the -47 will get to it's top speed long before the 190 will.
Hi,
actually dive tests did show a better intial dive acceleration for the 190A, while the P47 did gain a good advanatage afterward!!
This is probably related to the higher dragload of the FW190A, while the P47 keep more power + more weight.
Initially the weight is a handycap, cause it need to get accelerated, once fast the weight worklike thrust itself in a dive, so the P47 could dive faster.
I also doubt that the FW190 had a higher critical mach!!
Afaik the early P47 got a heavy elevator, but not the compression problems like the P38.
The wing aspect ratio of the P47 was very low, this in general is very good for a high critical mach. Also some dive tests did show rather good results and also the pilots in war (german and US) tell about the good P47 dive speed.
Greetings,
Knegel
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190A what? 5 or 8?
P-47D what? 11, 25 or 40?
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yes,
Judge: The defendant calls Widewing to the stand
I'd say the P-47 only because of its ability to not compress :O
the A8 seems to compress easily..or at least to me.
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Originally posted by Knegel
I also doubt that the FW190 had a higher critical mach!!
According to Eric Brown they actually did. See the videos I posted.
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The P-47's critical mach number was .82 at altitudes above 25,000 feet....and corresponded to 601 mph TAS.
I doubt seriously that the Fw-190A had the horsepower or the weight to match the Jug in a dive from extremely high altitudes where the Jug's turbo-supercharger gave it a tremendous advantage.
Which Fw-190 was Capt. Brown talking about? If he was talking about the D9 that might be a different matter....at least at medium altitudes.
Regards, Shuckins
P.S. Corky Meyer related a tale in a Flight Journal article about a radio-controlled Hellcat reaching .81 mach in a dive from high altitude. He believes the people controlling the Hellcat didn't understand the effects that such a high near mach speed had on piston-engined aircraft....the controls set in concrete, the tucking under of the nose.....and as a consequence flew it into the ground in the near-vertical dive.
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He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.
In Aces High the effects of compressibility is not modeled realistically; it is “easy mode” compared to real life. It would perhaps be difficult to model it accurately as the effects were individual to each plane. The P-38 for instance would nose over into an inverted almost vertical dive that was unrecoverable without dive flaps (that were later added to the design). Unfortunately for the P-38 pilots in Europe, their P-38s were never equipped with dive flaps and many plunged to their deaths trying to follow diving Germans.
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Early model P-47 would often break up in compressibility dives, and late model P-47 were given dive flaps (like on the P-38) to help pilots recover. Prior to the addition of dive flaps the P-47 pilots were trained in how to recover from compressibility dives, but it was a harrowing experience that would leave them bruised and battered at 2000 feet over enemy territory, often with structural damage to the control surfaces.
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Originally posted by Viking
He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.
In Aces High the effects of compressibility is not modeled realistically; it is “easy mode” compared to real life. It would perhaps be difficult to model it accurately as the effects were individual to each plane. The P-38 for instance would nose over into an inverted almost vertical dive that was unrecoverable without dive flaps (that were later added to the design). Unfortunately for the P-38 pilots in Europe, their P-38s were never equipped with dive flaps and many plunged to their deaths trying to follow diving Germans.
Brown is off a bit about the critical Mach of the P-47. Republic states that it is Mach .74 rather than .71. Placarded maximum permitted dive speeds at 10k are as follows:
P-47D: 500 mph IAS
P-51D: 500 mph IAS
P-38L: 440 mph IAS
F4U-1D 443 mph IAS
F6F-5: 449 mph IAS
Inasmuch as the Fw 190 uses the same wing section as the F4U (NACA 23015), I doubt that the 190 had a critical Mach greater than the P-47.
My regards,
Widewing
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Originally posted by Widewing
Brown is off a bit about the critical Mach of the P-47.
Brown was talking about tactical Mach number not critical (or limiting Mach number as he called it). Tactical Mach is the maximum speed you can still fight the aircraft. Critical/limiting Mach is the speed where you lose all control of the aircraft.
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Originally posted by Widewing
Inasmuch as the Fw 190 uses the same wing section as the F4U (NACA 23015), I doubt that the 190 had a critical Mach greater than the P-47.
Why would that be relevant? The Spitfire had the highest limiting Mach number of all piston engine fighters and still holds the record for highest Mach attained by a piston engined aircraft: Mach 0.891. Now, the Spitfire had an elliptical wing, but its wing section was nothing special.
The Me 109 was dived to Mach 0.79 in instrumented tests. Slightly modified, it was even dived to Mach 0.80, and the problems experimented there weren't due to compressibility, but due to aileron overbalancing. P-51 and Fw 190 achieved about Mach 0.80. The P-47 had the lowest permissible Mach number of these aircraft. Eric Brown observed it became uncontrollable at Mach 0.73, and "analysis showed that a dive to Mach 0.74 would almost certainly be a 'graveyard dive'".
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I'm confused......:confused: . Another thing why'd the P-38 have such a low mach number, i always assumed it was because of that long beautiful wing and those two propellors. I once heard that the most drag inducing part of a prop plane was the prop and that eliminating it would usually cause an increase of about 100mph. I think the Jug would win if someone sees me in TA one day ask me and i'll try it. :D
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The P-38s wing had a higher critical Mach number, but interference from the cockpit and engine nacelles reduced the planes overall critical Mach.
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Originally posted by Viking
Brown was talking about tactical Mach number not critical (or limiting Mach number as he called it). Tactical Mach is the maximum speed you can still fight the aircraft. Critical/limiting Mach is the speed where you lose all control of the aircraft.
Inasmuch as Brown never flew the P-47 in combat, I'd lean towards those who did.
Bob Johnson, with whom I had many long conversations, would dispute Brown's assertion that the P-47 was "useless" at 30,000 feet.
You will find that the RAF disagrees with Brown's opinion (as does much of the Flight Test Community on many issues) as well.
Read the RAF's P-47 Tactical Trials report. (http://www.wwiiaircraftperformance.org/p-47/p-47c-afdu.html)
Brown has had many detractors, not the least of which was Roland (Bee) Beaumont.
I would not hang my hat on Eric Brown's veracity.
My regards,
Widewing
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Originally posted by Viking
Why would that be relevant? The Spitfire had the highest limiting Mach number of all piston engine fighters and still holds the record for highest Mach attained by a piston engined aircraft: Mach 0.891. Now, the Spitfire had an elliptical wing, but its wing section was nothing special.
The Me 109 was dived to Mach 0.79 in instrumented tests. Slightly modified, it was even dived to Mach 0.80, and the problems experimented there weren't due to compressibility, but due to aileron overbalancing. P-51 and Fw 190 achieved about Mach 0.80. The P-47 had the lowest permissible Mach number of these aircraft. Eric Brown observed it became uncontrollable at Mach 0.73, and "analysis showed that a dive to Mach 0.74 would almost certainly be a 'graveyard dive'".
Herb Fisher performed over 200 high Mach dives in the P-47D-30, routinely exceeding Mach 0.80, with no issues whatsoever. Brown is an idiot. Here's a sample of actual test data at Mach 0.79, which according to Brown, would be a Graveyard dive. I have the original chart.
(http://home.att.net/~Historyzone/DiveChart.JPG)
(http://home.att.net/~c.c.jordan/Fisher-F-47D.JPG)
I have several more of Herb's charts and access to his log book. Fisher reached Mach 0.83 on several occasions. He thought the aircraft so safe, he took his 3 year-old son, Herb jr. along for a dive at Mach 0.80. I have photos of the event if you are interested... Here's one:
(http://home.att.net/~c.c.jordan/P-47JrAndSr.jpg)
From Herb Fisher Jr, via e-mail:
"Do not know if you have seen the “fastest toddler” picture, well the story is true. Also, in your article about my Dad, I saw drawings/sketches but not the actual PE219 P-47…here you go." Fisher had a special O2 mask rigged for his son. They hit 575 miles per hour during the dive.
Brown states that a dive at Mach 0.74 would certainly kill you, but a 3 year-old survived Mach 0.80..... :rolleyes:
My regards,
Widewing
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Originally posted by Widewing
Herb Fisher performed over 200 high Mach dives in the P-47D-30, routinely exceeding Mach 0.80, with no issues whatsoever. Brown is an idiot. Here's a sample of actual test data at Mach 0.79, which according to Brown, would be a Graveyard dive. I have the original chart.
The P-47D-30 was the first P-47 that could do that since among other structural improvements it had new blunt-nosed ailerons to improve controllability at high speeds, and to help in dive recovery at these high speeds, electrically-operated dive recovery flaps fitted on the undersurfaces of each wing. All P-47B, C and previous P-47D’s were deathtraps above Mach 0.73.
I could call you an idiot for not knowing that, but I won’t.
Originally posted by Widewing
Brown is an idiot
Eric M. Brown is undisputedly the world’s most experienced test pilot, and having flown all major types of allied and axis aircraft is in a unique position to comment on their relative performance. General Doolittle came to Farnborough to recruit the aid of RAE, and they specifically tested the P-38s and P-47 in service at that time (1943) against the captured 109s and 190s they had available. Calling this man an idiot is a grave insult and what respect I had for you is now gone.
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Hi,
wasnt the initial question, which plane reach faster the ground from 25k alt??
Although the P47 may have had some problems at highspeed, i dont think it was wing compression related. And although it might got stiff controlls, this should stop in lower altitudes, where the air got more thick and the planes dont reach that high mach numbers.
AND, i have no doubt that the P47 did dive faster to the deck, no matter how manouverable it was.
HP + weight should do the job by easy, and thats what the tests also show and what the pilots also are/was telling.
In Ah its the other way around.
(i already did offer my guess, why it is so).
Greetings,
Knegel
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P-51 could only dive to mach .80 ?
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Originally posted by Knegel
Although the P47 may have had some problems at highspeed, i dont think it was wing compression related.
It was very much wing compression related. When the plane approached compression speeds the wing would lose lift due to the forming of supersonic shockwaves at the leading edge. This loss of lift resulted in an uncontrolled nose down into a vertical dive. Before the installation of new ailerons and dive flaps with the D-30 model the only thing the pilots could do was throttle back and ride it out. Those that survived managed to pull out at very low altitudes. They were beaten and bruised by the heavy buffeting, and the control stick had beaten their legs black and blue. Early B and C model P-47s could also simply disintegrate in mid air.
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And yet 8th AF jug pilots considered diving away to escape from the jug, a futile attempt. I'll check Johnson's book again to see how many kills he got in a dive. I remember he commented on one of these kills: "They never learn".
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If we get back to the initial debate; let’s look at the physics involved and set up an experiment.
Let’s say we have two planes: Plane A and plane B.
Plane A
Weight: 1000kg
Thrust: 1000kg
Plane B
Weight: 2000kg
Thrust: 1000kg
Both planes are otherwise identical (size, shape, drag).
Now … if both planes are lifted up to altitude by balloon and dropped at zero speed, we can ask two questions:
1. Which plane will accelerate quickest initially?
2. Which plane will achieve the greatest terminal velocity?
The answer to the first question is Plane A. Initial acceleration is determined by the thrust to weight ratio. Plane A gets 1G of acceleration from Earth’s gravity, and another 1G of acceleration from its thrust (being equal to its weight). Plane B also gets 1G acceleration from gravity, but only 0.5G from its engine thrust (being only half of its weight).
The answer to the second question is Plane B. As speed increase the thrust to weight ratio becomes secondary to the weight+thrust to drag ratio. Plane B has 2000kg of weight and 1000kg of thrust and will therefore stop accelerating at a speed where the total drag is equal to 3000kg. Plane A having only a total of 2000kg of weight and thrust will stop accelerating when drag is 2000kg.
This is of course very simplified. When we are comparing two different planes with different aerodynamics and propulsion systems it becomes very complicated. One interesting thing that the RAE people found out dive testing Spitfires was that of the speed they achieved only 1% was due to propeller thrust. 3% was from exhaust thrust, and the rest was due to gravity. With propeller driven planes the thrust does not remain constant at different speeds. The propeller loses efficiency as speed increases, and thus the weight to drag ratio of the plane becomes even more important.
So which plane dives better, the Fw 190 or the P-47? I don’t think there is an easy answer to that question.
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Originally posted by bozon
And yet 8th AF jug pilots considered diving away to escape from the jug, a futile attempt. I'll check Johnson's book again to see how many kills he got in a dive. I remember he commented on one of these kills: "They never learn".
Which model P-47 did he score his kills in?
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Originally posted by Viking
The P-47D-30 was the first P-47 that could do that since among other structural improvements it had new blunt-nosed ailerons to improve controllability at high speeds, and to help in dive recovery at these high speeds, electrically-operated dive recovery flaps fitted on the undersurfaces of each wing. All P-47B, C and previous P-47D’s were deathtraps above Mach 0.73.
I could call you an idiot for not knowing that, but I won’t.
Eric M. Brown is undisputedly the world’s most experienced test pilot, and having flown all major types of allied and axis aircraft is in a unique position to comment on their relative performance. General Doolittle came to Farnborough to recruit the aid of RAE, and they specifically tested the P-38s and P-47 in service at that time (1943) against the captured 109s and 190s they had available. Calling this man an idiot is a grave insult and what respect I had for you is now gone.
Fisher's P-47 was specifically NOT fitted with the dive recovery flaps, nor was his P-47D-26-RA that he began the test program with. The D-26 was retired after cracks were discovered in engine A frame mountings. Dive recovery flaps generated too much drag and positive pitch-up. Fisher was testing transonic propellers and needed to exceed Mach 0.75, which the P-47 would not do with the recovery flaps deployed. Fisher used trim to initiate pull-out, just like every P-47 pilot was instructed to do.
I'll bet you think Yeager is another distinguished test pilot of great reputation too, right?
Brown has a long-time reputation within the Flight Test community of being a wind bag and has been frequently accused of misstatements. Many of his evaluations were diametrically opposed to those of other test pilots and his combat evaluation of the Fw 190D was literally laughed at Langley Field.
As it is, Brown's P-47 comments are not supported by the operational record, nor do they agree with many other test pilots who have vastly greater experience testing the Jug. Fewer P-47s were lost in dive related accidents than P-51s.
I came to the conclusion many, many years ago that Brown was not a reliable source for objective flight reports as he was remarkably opinionated and could not keep his personal opinion from contaminating his data. His feuds with fellow test pilots were well known and some persist to this very day.
Just because Brown says so, that doesn't make it true or accurate.
My regards,
Widewing
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"Inasmuch as the Fw 190 uses the same wing section as the F4U (NACA 23015), I doubt that the 190 had a critical Mach greater than the P-47."
I'd say that the wing area, aspect ratio and planform design (sweep angle) are as relevant as wing profile as far as the thickness values stay at reasonable levels when critical mach is concerned. In fact the sweep angle helps in getting higher mach than would be possible with straight leading edge with given thickness ratio.
P47 300 sq ft
Inner: Seversky S-3, outer: Seversky S-3 (thickness ratio??)
FW190 197 sq ft
Inner: NACA 23015.3, outer:NACA 23009
-C+
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Originally posted by Viking
Which model P-47 did he score his kills in?
21 of his kills came in a P-47D-5, two more in a P-47C-5... Brown's death trap. His last kills were in a D-21, I believe:rolleyes:
I will reiterate: Brown is an idiot.
My regards,
Widewing
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Quite arrogant of you to post such insults of an older gentleman on a public board.
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Originally posted by BlauK
Quite arrogant of you to post such insults of an older gentleman on a public board.
Based on WW's research and interviews, I'm not sure you could consider them insults.
Thanks for the information, WW, very informative as usual.
- oldman
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Well, Kurfy once called Carson an idiot and eventually got booted. Any bets? :D
-C+
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Originally posted by Viking
Early B and C model P-47s could also simply disintegrate in mid air.
Reference???
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“Two days later, as I lay on my bunk listening to the King Cole Trio, my reverie was rudely interrupted by a loud, eerie, whining drone. Suddenly, a loud thud punctuated the drone, followed by stark silence. I knew one of our planes had gone down. I prayed that the pilot had bailed out. I ran outside and climbed into my Jeep, along with a couple of fellow pilots. We could see the tell-tale plume of black smoke rising swiftly into the beautiful, sun-drenched sky. The beautiful sky gave us hope that our friend might be alright. As I plunged through the woods and rough terrain, it was impossible to see if a parachute was floating down. We finally reached a clearing in a clearing made by the Jug. Fallen trees, tree limbs, and loose dirt surrounded a crater in the earth twenty-odd feet deep and fifty-odd feet across. The plane had dived into the ground nose first and vertically!”
William M. Wheeler
Tuskegee Airman
332nd Fighter Group
302nd Fighter Squadron
“I was interested in evaluating three developments now in the P-47M. It had the new 360-degree-vision bubble canopy; it could climb to 40,000 feet without stopping to "rest" above 30,000 feet; and it had dive-recovery flaps to cure its former uncontrollable compressibility diving with no recovery possibility.”
Corky Meyer
Test pilot
“Gradually, the Group learned how to manage the Thunderbolt. Still, there was a new problem beginning to appear. Powerful fighters such as the P-47 and P-38 were encountering something relatively new to aviation; compressibility. This new generation of high-speed aircraft were capable of incredible speeds in a dive. Compressibility is a term used to describe what happens when localized airflow across a wing approaches transonic velocity. The resulting shock wave could lock the elevators as if in a vise. Pilots were running up against compressibility and they were dying. P-47’s and P-38’s were being flown straight into the ground, or even breaking up in flight. The learning curve was far steeper than it had ever been before. Pilots now had to learn how to deal with this new, terrifying phenomena. Testing showed that the Thunderbolt could be flown out of a terminal velocity dive as it descended into warmer air at lower altitudes. This is because as the plane continues down, the relative speed of sound goes up. Eventually, the aircraft’s Mach number will drop (although its actual airspeed does not) and the shock wave will dissipate, allowing the pilot to regain control again. Pilots were instructed to pull off the throttle, and avoid using too much up elevator trim. Too much trim, or too much back pressure on the stick could over-stress the airframe when the fighter began to respond to control inputs. Pilots who had flown the P-47 into compressibility came away with bruises to verify their adventure. The Thunderbolt’s ailerons would flutter as it exceeded its critical Mach limits, causing the stick to move violently from side to side; pummeling the inside of the pilot’s thighs black and blue.”
Warren M. Bodie, by the pen of Corey C. Jordan.
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P-47C Thunderbolt 41-6628 of the 495th Fighter Training Group USAAF crashed at Thorncliffe on the 3rd October 1944.
Crew / Passengers
Rank - if applicable
Service Number Position e.g. Pilot
Status
Quentin J Sella
2nd Lieutenant
O-710189 Pilot
Killed
Above is a photograph of Quentin J. Sella shortly after receiving his commission in February 1944, this appeared with his obituary in the Grand Rapids Press (one of the newspapers from the city he was from in Michigan) on the 30th October 1944. He had joined the USAAF as an officer cadet in 1942 being commissioned in early 1944. From April to September he served with the 33rd Fighter Squadron in Iceland, in June he was involved in a minor ground accident when the P-47 he was in ground looped when one brake failed. He arrived in England only a month before he was killed.
Mark stood by where the P-47 dived into the ground, being a natural spring the ground is very soft.
The aircraft had been flying as part of a 4 ship formation on a formation flying exercise, this aircraft was in the number 4 position. On entering cloud the formation became split up with the number 1 and 3 aircraft staying together and number 2 and 4 becoming separated. They were directed onto diverging courses by the flight leader to avoid the possibility of midair collisions. In the crash report it is assumed that 2nd Lt Sella became disorientated as his instruments may have been giving false reading. Because of this he lost control and the aircraft entered either a dive or spin, the aircraft fell into the ground in a vertical dive hitting very soft ground and deeply burying itself.
This photo showed the aircrafts canopy which had been jettisoned and fell some 400 yards from the crash site, 2nd Lt Sella obviously tried to bale out of his aircraft but due to the high-speed dive would have been unable to exit the cockpit due to the slipstream.
This photo shows the seen at the crash site, all that can be seen is the massive hole filled with mud and water.
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Originally posted by Widewing
I will reiterate: Brown is an idiot.
Brown is not, but you clearly are.
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Dive flaps have been mentioned a few times so far. The P-47D-40 has them, but the P-47N we have doesn't seem to have them. Why is this?
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Originally posted by Oldman731
Based on WW's research and interviews, I'm not sure you could consider them insults.
I suppose I can also call you one without it being an insult, because I disagree with you but I have worked as a researcher for several years?
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Originally posted by BlauK
I suppose I can also call you one without it being an insult, because I disagree with you but I have worked as a researcher for several years?
Truth is a defense, dude. If I were making things up and telling you they were real, particularly if they were things that I should expect other people to rely on, you might justifiably call me an idiot when you found out about it. My age, experience and rugged good looks don't really enter into the analysis.
- oldman (btw, you would not be the first to call me an idiot, either!)
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From Wikipedia:
Captain Eric Melrose "Winkle" Brown, CBE, DSC, AFC, FRAeS, RN is a former Royal Navy officer and test pilot who has flown more types of aircraft than anyone else in history. He is also the Fleet Air Arm’s most decorated pilot.,
Born in January 1919, he first flew when he was 18.
After World War II‚ Brown commanded Enemy Aircraft Flight, an elite group of pilots who test-flew captured German aircraft. That experience makes Brown one of the few men qualified to compare both Allied and Axis "warbirds" as they actually flew during the war. He flight-tested 53 German aircraft, including the Me 163 rocket plane and the Messerschmitt Me 262 jet plane.
On December 3, 1945, Brown made the world's first landing of a jet aircraft on an aircraft carrier. He landed a de Havilland Sea Vampire on the Royal Navy carrier HMS Ocean.
He flew aircraft from Britain, America, Germany, Italy and Japan, and is listed in the Guinness Book of World Records as holding the record for flying the greatest number of different aircraft. The official record is 487, but only includes basic types. For example Captain Brown flew several versions of the Spitfire and Seafire, and although these versions are very different they only appear once in the list.
He was the first to land a jet aircraft on a carrier, and also holds the world's record for the most carrier landings, 2,407.
He finally gave up his wings at 70 years old, but still lectures. He is a regular attendee of British Rocketry Oral History Programme (BROHP).
As we can all see he must have been a complete idiot (and British, a damn foreigner at that).
And then we have a real smart guy, who takes a three year old in the cockpit and dives an airplane to its limits testing experimental propellers, because only idiots would think that something could go wrong. But real pilots know that is NOT possible.
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:)
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Just to clarify.
It is quite possible that Mr. Brown is wrong in this particular topic. When you hear enough pilots testimonials of about any plane, you will find that they cannot probably agree about anything. The "Joint Fighter Conference" -report is a good example.
But starting to sling insults at these respectable veterans because of this is pretty low, IMO.
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Inexcusable is the word I would choose. I had a lot of respect for Widewing’s opinions; they seemed levelheaded and fairly well researched, and always polite. None of that matters now. He has shown his true nature.
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Originally posted by BlauK
Quite arrogant of you to post such insults of an older gentleman on a public board.
I must agree that I have been harsh. For that I apologize. However, Brown has made repeated statements over the years that have been disputed as not being true or accurate. I'll say it again, he is not held in wide regard within the Flight Test Community. He is regarded highly by aviation buffs who often believe everything they read in print.
Brown's opinions are often not supported by any documentation. If fact, the documentation often shows that his opinion is just that, an opinion, purely anecdotal in nature.
When challenged, as he was by former Flying Tiger and Republic test pilot Ken Jernstedt over his published assertions against the P-47, Brown replied that he (Jernstedt) was entitled to his opinion. Jernstedt was lead test pilot on the P-47N and XP-72 programs... Ken Jernstedt logged thousands of flight hours testing and wringing out P-47s. If I wanted an opinion on the P-47, I would have gone to Jernstedt, certainly not Brown.
My regards,
Widewing
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Originally posted by TimRas
From Wikipedia:
C
On December 3, 1945, Brown made the world's first landing of a jet aircraft on an aircraft carrier. He landed a de Havilland Sea Vampire on the Royal Navy carrier HMS Ocean.
As we can all see he must have been a complete idiot (and British, a damn foreigner at that).
TimRas, using wikipedia as a source is not a good idea.
Brown was not the first man to land a jet powered fighter on a carrier...
On November 6, 1945, Marine Lt. J.C. West made the first carrier landing in an aircraft powered only by a jet engine. His Ryan FR-1 suffered a failure of the R-1820 radial. He feathered the propeller and proceeded to fly to and land the Ryan aboard the USS Wake Island flying only on its GE J31 turbojet. This is common knowledge and undisputed fact.
Ryans were often flown on jet power only.
(http://www.centennialofflight.gov/essay/Aerospace/Ryan/Aero34G6.jpg)
If Eric Brown claims he was first, he does so in the face of the truth.
My regards,
Widewing
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:aok Ww.
I certainly know not to trust any single source alone. Actually Mr. Brown's testflights with a captured Bf109G (with wing cannons) have e.g. been the source for a commonly repeated (in several "average" books) misquote of the max speed of any 109G. Not likely his fault (the misquotes), but I did not know that when I first heard of the man, and built a prejudice pretty much on wrong assumptions.
I have not yet read his latest book, Wings on my Sleeve, and cannot therefore have much of an opinion of his opinions. However, I met him in Duxford last summer, and found him a very friendly and polite gentleman.
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Generally the RAE results on dive testing of the P-47 are quite similar as tested (http://mitglied.lycos.de/luftwaffe1/flight/compressibllity/flight_compress.html) by Republic. There is minor differences in the mach number values (probably due to measurement errors) but the phenomena and the effects are pretty much the same.
BTW I do think that we don't need name calling etc. here.
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Originally posted by Viking
It was very much wing compression related. When the plane approached compression speeds the wing would lose lift due to the forming of supersonic shockwaves at the leading edge. This loss of lift resulted in an uncontrolled nose down into a vertical dive. Before the installation of new ailerons and dive flaps with the D-30 model the only thing the pilots could do was throttle back and ride it out. Those that survived managed to pull out at very low altitudes. They were beaten and bruised by the heavy buffeting, and the control stick had beaten their legs black and blue. Early B and C model P-47s could also simply disintegrate in mid air.
Hi,
afaik the P47 could get recovered as long as it got trimmed up. The main problem imho was the to heavy forces.
Of course all normal wings got compression related problems around mach 0.75, but if i look to the max dive speeds of the P47 i only can conclude that the wing compressions wasnt the main problem, rather the not very effective elevator at this speed.
Thats rather similar to the 109, if it was trimmed for level flight and the trim system got frozzen, the pilot also couldnt recover, on the other side, if the 109G pilot raised the trim with power at highspeed, the g forces could rip of the wing.
Steep dives around mach 0,75 was dangerus for every WWII plane, but not many got to this speed by easy.
After all reading i got the conclusion that the P47´s dive acceleration at higher speeds in combination with the needed missing pilot experience was the cause of the P47 crashs, not the in general absolut dangerus plane. Same count for the 109!
Actually i still doubt the RAE results on the Spitfire, thats abosut again the war experiences, where the 109´s and FW190´s could leave the Spits behind by easy. I still think they had bad measurement mistakes, what was rather normal at that time.
btw, was the pilot able to trim the P47 at highspeed, like the 109 and 190 pilot could(as long as the trim wasnt frozen due to wrong lubricant)??
Ww, to call a pilot like Brown a idiot in a public forum is not very honourable!! Many pilots tend to overstate and dont have a good sence for scientific work, but it looks to me thats in the nature of many fighter pilots.
Carson made even more bad statements, specialy regarding the 109, and that in a attempt to proof the bad design of the 109 in a "scientific" layout. Such articels are way more bad than the obvious opinion like statements of Mr. Brown.
Greetings,
Knegel
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Originally posted by Knegel
Ww, to call a pilot like Brown a idiot in a public forum is not very honourable!! Many pilots tend to overstate and dont have a good sence for scientific work, but it looks to me thats in the nature of many fighter pilots.
Carson made even more bad statements, specialy regarding the 109, and that in a attempt to proof the bad design of the 109 in a "scientific" layout. Such articels are way more bad than the obvious opinion like statements of Mr. Brown.
Greetings,
Knegel
I agree... I should have simply bitten my tongue. Brown is certainly not an idiot.
He is in my opinion, however, a shameless self-promoter. In that regard, he reminds me of Thomas Lanphier and his obsession with his claim of shooting down Yamamato. To this day, many still repeat this as the gospel truth, despite the fact that it was known from the day it happened that Lanphier's claim was false, as was his claim of shooting down a Zero as well.
Brown insinuates that he was the impetus to the installation of dive recovery flaps on the P-47. Naturally, he ignores the fact that NACA was working on this years before his test flight in the P-47.
In point of fact, NACA suggested the solution to Lockheed in the autumn of 1942. Lockheed developed the flaps in their own wind tunnel and was flying a P-38G fitted with dive recovery flaps in February of 1943. That was a full year before Brown flew the P-47. The AAF told Lockheed to share their data with all manufacturers. In January of 1944, a modified P-47D-22-RE was flown with Republic's dive recovery flaps installed. This was STILL before Brown had flown the P-47.
It is things like this that cause me to take many of Brown's comments with a grain of salt. It also irritates me when people accept what he says as the holy grail without question.
Thus, my over-reaction....
My regards,
Widewing
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viking, non of these quotes really say that P47 were breaking in mid air. The only place something such as this is mention is in the line:
"P-47’s and P-38’s were being flown straight into the ground, or even breaking up in flight."
It is not even clear if this relates to P38 or P47 and if this was a one-case or a common phenomenon. It is also not clear whether they were being flown into the ground because compressibility was a "new phenomenon" and pilots did not know how to respond (or were careless), or because it was impossible to recover. If the critical mach was 0.9 and they could reach it, would have they not compressed and crashed? The quote clearly relates to the period when these planes were being introduced into service.
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Originally posted by Knegel
Hi,
afaik the P47 could get recovered as long as it got trimmed up. The main problem imho was the to heavy forces.
No the P-47 could not be trimmed out of a compressibility dive. The controls and trim tabs were completely ineffective until the Mach number was reduced to less than 0.73. Trying to trim out of dives killed many pilots by overloading the airframe when the controls became responsive again.
Originally posted by Knegel
Of course all normal wings got compression related problems around mach 0.75, but if i look to the max dive speeds of the P47 i only can conclude that the wing compressions wasnt the main problem, rather the not very effective elevator at this speed.
Thats rather similar to the 109, if it was trimmed for level flight and the trim system got frozzen, the pilot also couldnt recover, on the other side, if the 109G pilot raised the trim with power at highspeed, the g forces could rip of the wing.
It is completely different than the 109. The 109 had a “flying tail” trim before the term was even invented. The whole tail plane would move with trim and thus remained effective at any and all speeds (theoretically even supersonic speeds). Trimming too much would of course overload the airframe. The P-47 had trim tabs that were totally ineffective during compressibility dives. Losing control of the aircraft at Mach 0.73 and having no option than “riding it out” down to less than 10,000 feet where control was reestablished is totally unacceptable in a high-speed high-altitude fighter as Brown and the RAE found out. The problem was not as bad as with the P-38s that often lost their tail section in dives, but bad enough.
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Originally posted by bozon
viking, non of these quotes really say that P47 were breaking in mid air. The only place something such as this is mention is in the line:
"P-47’s and P-38’s were being flown straight into the ground, or even breaking up in flight."
It is not even clear if this relates to P38 or P47 and if this was a one-case or a common phenomenon. It is also not clear whether they were being flown into the ground because compressibility was a "new phenomenon" and pilots did not know how to respond (or were careless), or because it was impossible to recover. If the critical mach was 0.9 and they could reach it, would have they not compressed and crashed? The quote clearly relates to the period when these planes were being introduced into service.
The early P-47s (B series and perhaps the very early C series) had fabric covered control surfaces. These would often fly apart during compressibility dives dooming the plane and pilot. Also before a recovery procedure was worked out pilots would try to trim out of the dive resulting in overloading the airframe when the plane reached lower altitudes where the controls became effective again. Or in the words of Warren Bodie (a man I believe Widewing respects greatly): “Pilots were running up against compressibility and they were dying.”
Eric Brown test flew the P-47 with a Mach meter installed and found that the speed at where control was lost was Mach 0.73. This is INDISPUTABLE, and totally unacceptable in a high-speed high-altitude fighter. And I’ll take the word of an accomplished test pilot like Eric Brown who actually test flew the plane in question over some armature internet historian who’s peeved that his pet warbird got a bad rep.
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Originally posted by Viking
The early P-47s (B series and perhaps the very early C series) had fabric covered control surfaces. These would often fly apart during compressibility dives dooming the plane and pilot.
As far as I remember, B series never saw combat and C was replaced by D very early on.
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Originally posted by Viking
Eric Brown test flew the P-47 with a Mach meter installed and found that the speed at where control was lost was Mach 0.73. This is INDISPUTABLE, and totally unacceptable in a high-speed high-altitude fighter.
The C model had metal covered control surfaces as a result of the flaws found in the B model, which as Bozon said, never saw combat. And, for you to say that Mach .73 was where the P-47 lost control is indisputable, is well...disputable, as there are many other credible sources in the aviation history world that counter it.
Personally, I don't understand why you're so dug in on this one--unless you've got some sort of agenda.
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The B-series, indeed, did NOT see combat....being mainly test aircraft. One of the early dog-ships in this series shed its tail during a test dive. This was at a time when the effects of compressibility were first being encountered and engineers in nearly every company producing modern fighters for the military were at a loss as to its causes.
Corky Meyer flew one of these early P-47Bs in 1943, and was cautioned by Republics people to not exceed the dive limit speed. That the Jug was capable of getting rid of an appalling amount of altitude in a short amount of time was evidenced in the warning not to attempt a split-s at less than 15,000 feet of altitude.
The Jugs tail structure was strengthened, and the aircraft went into combat. Statements made previously that suggest the P-47 pilots routinely dove their aircraft past their German foes and into the ground are gross exaggeration.
While I admire Capt. Eric Brown and have enjoyed reading "Duels in the Sky" and some of his aviation articles, I take some of his statements with a grain of salt. While he has flown literally hundreds of aircraft his time in some of them is not extensive. The statements of test and combat pilots who were intimately familiar with the aircraft and all of its foibles should have more weight.
Corky Meyer flew a P-47M in 1944. Republic's engineers told him that test pilot Parker Dupouy had dived the Jug vertically to its maximum Mach number of .868 and made a very successful dive recovery-flap pullout. This was 61mph faster than the P-47s compressibility entry Mach number. Corky took the P-47M to 30,000 feet and pushed over into a 60-degree dive and ran the combined Mach number/airspeed indicator up to .80 - well past its compressibility limit Mach number. He extended the dive recovery flaps which provided a stick-free 4G pullout that brought the fighter back below its airspeed limit within a "few easy seconds."
Macky Steinhoff has stated that German pilots feared the Thunderbolt because of its "extraordinary ability to attack in a nose dive." Robert Johnson and every pilot who went to war in the Jug states the same thing.
If a Jug was close to a Luftwaffe fighter, neither pilot would give a fig for its chances of escaping the Thunderbolt in a dive.
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Who's on first?
190A5 & p47 are both close enough in dive ability, and speed that it makes more difference who gets nose down & unloaded first, than which is faster.
I know, I helped a player test exactly this about 3 years back.
So, the guy in the lead (the one being shot at) has the advantage.
Lag time, reaction time, will put him out of the other guys guns long enough to accelerate to top speed at which point the other plane can't close the range.
Now, when they come OUT of the dive is another story.
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Originally posted by Stoney74
Personally, I don't understand why you're so dug in on this one--unless you've got some sort of agenda.
He has always had an agenda, albeit he has never been strident about it like some others. He likes the Luftwaffe aircraft. Just like those who like American, British, Japanese or Italian aircraft, he doesn't like to see them bashed. I can sympathize. I think that the Antons in AH2 need some adjustments to the flight models to improve their turn radius. I think the 109's flaps are now TOO good. I can agree with some of the things the Luftwaffe fans are asking for, and disagree on some others.
What bothers me is his reliance on Brown. I'd wager that Brown had less than 10 hours in P-47s. Guys like Parker Dupouy and Ken Jernstedt had thousands of test hours in Jugs. Both of these guys were veterans of the AVG, with vastly more combat experience than Brown. Then there's Lowery Brabham who is without peer when it comes to knowledge of the Thunderbolt.
Viking is arguing that the P-47 was a death trap. He uses Brown's figure of Mach 0.73 like God etched it on a tablet. Brown is wrong. He's wrong in many ways.
You can look at the paper gripen provided a link to. You can examine the test data from the XP-47J which attained 493 mph at 33,350 feet early in the flight test program (Mach 0.737 in level flight) and 507 mph at 34,300 feet later (Mach 0.76 in level flight). Test pilot Mike Richie reported moderate buffeting and increasingly strong lateral stick oscillation at that speed. Nothing I've looked at comes close to showing the P-47 at Mach 0.73 being out of control. Note that the XP-47J used the same wing as the P-47D-15. This fighter was designed and engineered to defeat the Fw 190. The prototype demonstrated that this goal had been easily exceeded. However, the issue of range dogged the XP-47J and the AAF was already changing their image of what they wanted. Republic responded to this with the superlative XP-72, which still used the efficient Michael Gregor (another ex patriot Russian) designed Seversky S3 wing.
Viking just sat through a seminar by Brown and was impressed with him. I've sat down with many distinguished pilots, some of them extremely experienced test pilots. All were impressive. Nonetheless, I would not hang my hat on their word alone. One fellow insisted that his P-47 had gone supersonic in a dive. I gently mentioned that this was not really the case, but a common instrument error associated with shock wave formation at the pitot tube orifice. He would have none of it, he went supersonic and that was that... There was no point in explaining that the propeller drag alone made his claim impossible. This guy had made up his mind and wasn't about to let anyone confuse him with facts. So be it. His comments on operational matters were spot-on. Separate the wheat from the chaff, that's the purpose of historians.
P-47s suffered no more from compressibility than did any other modern fighter of the era. The fact that it operated at extreme altitudes made encountering compressibility more common place. The F4U and F6F were placarded with lower max speed limitations. The fact that these fighters rarely operated above 25,000 feet meant that they had much fewer opportunities to get into long, high-speed dives. Still, there were fatalities from diving these fighters too fast as well. There are documented crashes of P-40s where compressibility was ruled the cause. It was not uncommon for 109s and 190s to go straight into the ground as well. Some were captured on gun camera film.
After all is said and done, Viking was simply stating that he believes that HTC should model a lower critical Mach for the P-47 so that his beloved 109s and 190s don't get their backsides handed to them when Combat Tour debuts.
My regards,
Widewing
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Why Viking/Gsholz is hanging it all on Brown is simple.
Here is 1 (one) allied test pilot who backs up his belief about the 47.
So now he'll hang on to it like a pit bull.
Bronk
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Originally posted by Viking
No the P-47 could not be trimmed out of a compressibility dive. The controls and trim tabs were completely ineffective until the Mach number was reduced to less than 0.73. Trying to trim out of dives killed many pilots by overloading the airframe when the controls became responsive again.
It is completely different than the 109. The 109 had a “flying tail” trim before the term was even invented. The whole tail plane would move with trim and thus remained effective at any and all speeds (theoretically even supersonic speeds). Trimming too much would of course overload the airframe. The P-47 had trim tabs that were totally ineffective during compressibility dives. Losing control of the aircraft at Mach 0.73 and having no option than “riding it out” down to less than 10,000 feet where control was reestablished is totally unacceptable in a high-speed high-altitude fighter as Brown and the RAE found out. The problem was not as bad as with the P-38s that often lost their tail section in dives, but bad enough.
Hi,
what i meant is: Every experienced pilot could have trimmed the plane a bit upward before a dive!!!
As you can see in my question regarding the trim, i know about the 109/190 trim system.
The P47B never saw combat, therefor the statements are absolut not valid, otherwise we also could use the 109F prototypes, where the wings felt off a bit early to make statements about the 109G and K.
Actually the 109´s had problems to get trimmed, specialy in high alt, where the system froze, until they found that a special lubricant was needed to prevent the freezing.
Originally posted by Widewing
I think the 109's flaps are now TOO good. I can agree with some of the things the Luftwaffe fans are asking for, and disagree on some others.
Hi,
Not the 109 flaps are too good, almost ALL flaps are too good!!
The current flaps are so far outside of the physical law, they damage the realism of AH much and imho make it almost to an arcade game.
If i see a Spitfire using its flaps to turn like mad, i could get crazy. The Spitfire only had one step and it was made to slow the plane down and this flaps, same like ALL full extended flaps, dont help while turning!!
In AH the flaps work more like big ballons, even the vertical "hoovering" work better with extended flaps, thats a joke. And i can bank a plane almost 80% close to stall speed without to lose altitude, if i use full flaps. I also can roll the plane at this speed with rather smal alt lost. Do flaps novadays create sideward lift and -g lift, depending to the bank angle??
The turnradius of the FW190 seems to be ok to me!! Imho it have to much lift at slow speed, resulting in the very strange landing behaviour, where the plane tend to lift up again and again, even below 100mph.
Reduce the lift a bit, increase the drag a bit and specialy increase the power!!
Then we get the highspeed power plane, that live by its high cruise speed and high stage of energy/power.
The 190A5-8 couldnt turn sustained with the 109s, but it should be able to outzoom the 109F-109G6, Spit5-16 and HurriIIc out of highspeed. The inertia advantage of around 1000kg + the power advantage of up to 300hp should do the job!!
Curently the 190A´s, but also the D9, miss the outstanding initial acceleration, while the the acceleration above 400mph is too good.
More drag = less high speed accceleration
More power = better slow speed acceleration/climb, better upzoom behaviour.
Much less airfoil related lift= bringing the climb back to the realistic values and stopping the much to good slow speed handling.
A more big max AoA with flaps= Stopping the strange landing bahaviour.
Greetings,
Knegel
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Anybody have any data on Seversky S-3 wing profile?
-C+
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Originally posted by Charge
Anybody have any data on Seversky S-3 wing profile?
-C+
No data, but a cross section...
(http://www.ae.uiuc.edu/m-selig/ads/afplots/s3.gif)
My regards,
Widewing
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Originally posted by Stoney74
And, for you to say that Mach .73 was where the P-47 lost control is indisputable, is well...disputable, as there are many other credible sources in the aviation history world that counter it.
Then please provide these “other credible sources”.
Originally posted by Shuckins
Corky Meyer flew a P-47M in 1944. Republic's engineers told him that test pilot Parker Dupouy had dived the Jug vertically to its maximum Mach number of .868 and made a very successful dive recovery-flap pullout. This was 61mph faster than the P-47s compressibility entry Mach number. Corky took the P-47M to 30,000 feet and pushed over into a 60-degree dive and ran the combined Mach number/airspeed indicator up to .80 - well past its compressibility limit Mach number. He extended the dive recovery flaps which provided a stick-free 4G pullout that brought the fighter back below its airspeed limit within a "few easy seconds."
The P-47M had a completely redesigned semi-laminar flow wing that had a much higher critical Mach than earlier P-47 wings. Speed and dive figures for the (X)P-47M, N or J are not representative of the P-47C or D series.
Originally posted by Widewing
You can examine the test data from the XP-47J which attained 493 mph at 33,350 feet early in the flight test program (Mach 0.737 in level flight) and 507 mph at 34,300 feet later (Mach 0.76 in level flight). Test pilot Mike Richie reported moderate buffeting and increasingly strong lateral stick oscillation at that speed. Nothing I've looked at comes close to showing the P-47 at Mach 0.73 being out of control. Note that the XP-47J used the same wing as the P-47D-15.
Your “note” is inaccurate or an outright lie. The XP-47J wing was redesigned. So much in fact that they had to reduce armament to only six guns. The whole airframe was in fact redesigned. Speed and dive figures for the (X)P-47M, N or J are not representative of the P-47C or D series.
Now, is there is a reason why you and others here only present Mach figures for the P-47M and the experimental J (of course neglecting to include that they were completely redesigned and nothing like the C or D)? Perhaps you have an agenda? Or perhaps Brown is correct in that the RAE were the only ones to actually DO Mach speed test that early in the war.
Originally posted by Widewing
After all is said and done, Viking was simply stating that he believes that HTC should model a lower critical Mach for the P-47 so that his beloved 109s and 190s don't get their backsides handed to them when Combat Tour debuts.
Please quote where I was “stating” that. You can’t, because you’re lying through your teeth. I’ve stated that the effects of compressibility is “easy mode” in Aces High … for ALL aircraft, so critical Mach is not so “critical” as to even be important in AH. Of course some aircraft benefit from this more than others, but such is life. We will have to wait and see what sort of threat the P-47 will pose to the LW in CT … and indeed if CT will be an accurate recreation of the European theatre. In R/L the LW would for the most part wait until the P-47s RTB’ed before attacking the bombers. If this option is made available to the LW I’m afraid the P-47 will take a backseat to the P-38 and P-51. However if CT is more a recreation of Hollywood the whole issue is irrelevant to me since such a game will hold little interest for me.
Originally posted by Knegel
what i meant is: Every experienced pilot could have trimmed the plane a bit upward before a dive!!!
What good would that do except perhaps preventing the plane from driving too fast by forcing the nose up?
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Originally posted by Viking
The P-47M had a completely redesigned semi-laminar flow wing that had a much higher critical Mach than earlier P-47 wings. Speed and dive figures for the (X)P-47M, N or J are not representative of the P-47C or D series.
Utter nonsense. The YP-47Ms were built as re-engined P-47D-27-RE types. There was no XP-47M. Production Ms were built from P-47D-30-RE airframes, having the same wing. All Ms have P-47D-30 serial numbers and were from the group built to the same contract (contact #W535-AC-29279-17). The J used the same wing as all other Jugs. Gun reduction was done per AAF specification. The P-47N was fitted with wing extensions that included fuel tanks. The wingtips were squared off, but the airfoil is still the Seversky S3.
Your “note” is inaccurate or an outright lie. The XP-47J wing was redesigned. So much in fact that they had to reduce armament to only six guns. The whole airframe was in fact redesigned. Speed and dive figures for the (X)P-47M, N or J are not representative of the P-47C or D series.
Now, is there is a reason why you and others here only present Mach figures for the P-47M and the experimental J (of course neglecting to include that they were completely redesigned and nothing like the C or D)? Perhaps you have an agenda? Or perhaps Brown is correct in that the RAE were the only ones to actually DO Mach speed test that early in the war.[/B]
Please, stop working so hard at being wrong. All production P-47s employed the Seversky S3 wing. The XP-47J used the S3 wing, lightened structure, but the same airfoil. Don't believe me? Do some research.... I spent many hours in the Republic Aviation archives housed at the Cradle of Aviation Museum researching the piece I wrote for their website (found here) (http://www.cradleofaviation.org/history/aircraft/index.html)
The only P-47 to fly with a laminar flow wing was a modified P-47B, the XP-47F.
Better yet, please provide a source that shows any production P-47 employing anything other than the S3 wing.
"Please quote where I was “stating” that. You can’t, because you’re lying through your teeth. I’ve stated that the effects of compressibility is “easy mode” in Aces High … for ALL aircraft, so critical Mach is not so “critical” as to even be important in AH. Of course some aircraft benefit from this more than others, but such is life. We will have to wait and see what sort of threat the P-47 will pose to the LW in CT … and indeed if CT will be an accurate recreation of the European theatre. In R/L the LW would for the most part wait until the P-47s RTB’ed before attacking the bombers. If this option is made available to the LW I’m afraid the P-47 will take a backseat to the P-38 and P-51. However if CT is more a recreation of Hollywood the whole issue is irrelevant to me since such a game will hold little interest for me.
[/B]
Come on Viking, we can read between the lines... If you were not trying to influence things, why even start this debate?
By the way, with the arrival of the P-47D-25, Jugs had the range to reach the western outskirts of Berlin from Britain. As it is, by mid 1943, with the fitting of 108 gallon belly tanks and plumbing, the P-47s could fly as far east as the Rhine. With the coming of the P-47D-25 and later models, they had adequate, if not spectacular range. By August of 1944, range was moot as most P-47s were all based in France.
My regards,
Widewing
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Widewing-
I don't mean to get in the middle of this but you state that "there was no XP-47M" but yet on that article from the Cradle of Aviation Museum website states:
This is the only existing photo of the "unofficial" XP-47M test mule.
Ok, so it says "unofficial" but does that mean it didn't exist? I guess what I am saying is I don't follow what you were trying to say.
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Originally posted by DiabloTX
Widewing-
I don't mean to get in the middle of this but you state that "there was no XP-47M" but yet on that article from the Cradle of Aviation Museum website states:
This is the only existing photo of the "unofficial" XP-47M test mule.
Ok, so it says "unofficial" but does that mean it didn't exist? I guess what I am saying is I don't follow what you were trying to say.
You have to remember that this aircraft was an in-house project, paid for out of Republic's R&D budget. It was constructed from a P-47C-5-RE and began flying months before the requirement for the P-47M came down from the AAF. Chief test pilot Carl Bellinger said that the XP-47M tag was applied in retrospect, and unofficially. When the AAF layed out their specification, Republic rolled out the factory hotrod P-47C. After the AAF reviewed the flight data, Republic was given the task of building three fighters with the same R2800 C series engine as installed in the P-47C. These were built from P-47D-27s taken right from the production line and designated YP-47Ms. So, there never was a sanctioned XP-47M, just a super fast P-47C.
By the way, that same P-47C was later the early testbed for the extended wet wing that was eventually used on the XP-47N.
My regards,
Widewing
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Thanks Widewing, I just didn't understand what you were implying. I love the P-47 and that article will make for some great late-night reading when I have nothing to do here at work. Thanks for the clearification and the great posts you do here!
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Originally posted by Viking
Then please provide these “other credible sources”.
Widewing, do you have a copy of Hoerner's book, "Fluid Dynamic of Drag"? I think it has a table listing WWII critical mach numbers that include the P-47, and since it's a textbook used by almost every aerodynamic engineer in the world, it may satisfy Vikings definition of "credible".
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Originally posted by Stoney74
Widewing, do you have a copy of Hoerner's book, "Fluid Dynamic of Drag"? I think it has a table listing WWII critical mach numbers that include the P-47, and since it's a textbook used by almost every aerodynamic engineer in the world, it may satisfy Vikings definition of "credible".
I don't have a copy Stoney, but I'll bet it's an interesting read.
My regards,
Widewing
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Originally posted by Viking
What good would that do except perhaps preventing the plane from driving too fast by forcing the nose up?
Is that a joke question??
The pilot could push the stick until he notice compressibility effects, then its much more easy to get out of the dive. Stick forces are a major factor while getting out of a high speed dive. The FW190 and Bf109 trimsystem(used in all modern jets as well) was a good solution to overcome this, a up trimmed plane in a highspeed dive would have a very simmilar result.
But of course it also would help not to get into the critical mach.
Anyway, the P47 did proof its high alt escort abilitys, history have proofen the RAE wrong, so there is not much left to argue.
If the P47C was not combat worthy in high alt, the LW wouldnt have waited until the P47´s had to return to base. The P47s was a very good escort planes, specialy in high alt, where their super charger gave them a real advantage.
History tell us this: FW´s and 109´s was able to disengage Spits and Hurris in a dive, but not P47´s. Of course, at speeds around mach 0,75 no pilot had to fear a attack, cause at this speeds it was rather difficult for every piston engined WWII plane to manouver. Even the P51 and Spitfire was nothing more than stiff, specialy while rolling, at this speeds.
Greetings,
Knegel
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"No data, but a cross section..."
Thx! It is hard to come by any info of those older wing profiles. It would also be interesting to find a cross section picture of the wing profile used in Bf109: NACA 2R1 14.2/ NACA 2R1 11.35. The books I have do not tell what kind of form 2R1 actually is.
Looking the S-3 profile it seems that the pressure build-up is very much different between upper and lower side and would therefore induce pretty much different shock waves between upper and lower side which may cause either up or down pitch of wing depending of how evenly the pressure changes between the upper and lower sides. That depends of the placing of maximum thicknesses and their relation to chord centerline.
http://upload.wikimedia.org/wikipedia/en/1/1c/FAA-8083-3A_Fig_15-9.PNG
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Originally posted by Widewing
After all is said and done, ...
Widewing [/B]
... a hell lot more is said than done!
:rofl :D :rofl
Sorry Widening could not resist.
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This topic went for 50-something pages over on the IL-2 board.
The final conclusion was, JFK was killed by a conspiracy.
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Fnord!
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Originally posted by Widewing
Come on Viking, we can read between the lines... If you were not trying to influence things, why even start this debate?
I did not start this debate. There are people debating on this forum that no longer play the game … some never played the game. Are you saying these people also try to “influence things” by debating here? What you “read between the lines” is your own preconceptions and bias.
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Originally posted by Knegel
Is that a joke question??
The pilot could push the stick until he notice compressibility effects, then its much more easy to get out of the dive. Stick forces are a major factor while getting out of a high speed dive. The FW190 and Bf109 trimsystem(used in all modern jets as well) was a good solution to overcome this, a up trimmed plane in a highspeed dive would have a very simmilar result.
No it wouldn’t. Normal trim-tabs are also rendered useless by compressibility so when the elevators are affected so are the trim-tabs. Remember that while IAS remains relatively low at 30k, even in a high speed dive, if the plane enters a compressibility dive the IAS will increase drastically as the plane descends. When the plane comes out of compressibility and the trim-tabs suddenly work again in the now much more powerful airstream they can over-G the plane beyond the pilot’s ability to compensate due to the heavy stick forces. The recovery procedure developed for the P-47 reflects this; before diving the trim was to be set to neutral.
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Hi,
afaik the tailwing in general compress after the main wing(the P38 is rather a exception due to its unique design)!!
Therefor i think the problem is rather stickforce related.
The problem is, the compressing wings start to produce a downward movement, to counter this, the pilot would need a rather big elevator variation, but this need a to high force. If the plane is already trimmed upward, the plane would move up by itself if it get to fast.
But anyway, i dont know any combat report that describ similar problems like the P38 had, and regarding the P38 they also wrote that the problem wasnt the critical mach in general, but the extreme acceleration, which brought the P38 suprising fast into its critical mach. This still would have happen if the critical mach would have been mach 0,78.
And even the P38´s didnt crash, if they got into this situation, they simply lost a lot altitude, until they reached more thick air, where they slowed down and recovered.
The only WWII planes i know, which had a real death trap behaviour was the 262 and 163(the arado probably as well). The missing propeller drag and advanced aerodynamic couldnt help to slow the plane down, even in thick air, as result this planes was very limited regarding the dive, though their critical mach was rather high.
Some 262 got lost due to this, but also regarding the 163 this behaviour was known.
Greetings,
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Originally posted by Knegel
Hi,
afaik the tailwing in general compress after the main wing
That would depend on the relative thickness of the tailplane vs. the wing.
Originally posted by Knegel
If the plane is already trimmed upward, the plane would move up by itself if it get to fast.
Isn’t that what I said earlier that you protested against by calling it a “joke question”?
Originally posted by Viking
What good would that do except perhaps preventing the plane from driving too fast by forcing the nose up?
Certainly looks that way to me. :)
Originally posted by Knegel
But anyway, i dont know any combat report that describ similar problems like the P38 had, and regarding the P38 they also wrote that the problem wasnt the critical mach in general, but the extreme acceleration, which brought the P38 suprising fast into its critical mach. This still would have happen if the critical mach would have been mach 0,78.
And even the P38´s didnt crash, if they got into this situation, they simply lost a lot altitude, until they reached more thick air, where they slowed down and recovered.
The P-38s would often lose their tails in compressibility dives. Even while testing the new dive flaps the Lockheed test pilot lost the tail section of his P-38 and had to bail out. And even with the flaps extended the P-38 could suffer structural damage in dives. The P-38 was a fragile plane compared to most other fighters, often coming home with bent wings or tail sections after combat.
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Originally posted by Viking
The P-38 was a fragile plane compared to most other fighters, often coming home with bent wings or tail sections after combat.
More unsubstantiated baloney...
You know, if you keep posting nonsensical garbage,like the above, you are going to get reamed so much that you'll be able to pass a watermelon without so much as squinting... BOHICA!
My regards,
Widewing
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Originally posted by Widewing
More unsubstantiated baloney...
P-38 was limited to only 6 G. Of course you know this because we have had this discussion before:
http://forums.hitechcreations.com/forums/showthread.php?threadid=101459
Of course you skulked away without answering my question “So a P-38 would not survive 8 G's?” It was fragile.
From p-38online.com:
“After extensive testing, the answer to the problem was the use of a dive flap (or brakes). These flaps would be attached to the main spar under the wing. This would offset the loss in lift while in high-speed dives, and would allow the pilot to remain in control throughout the dive. Test pilots Tony Levier and Milo Bircham began a series of dive tests with the flaps. Lt. Benjamin Kelsey was sent by the Air Corps to evaluate the progress of the dive flaps. He took the modified P-38 and proceeded to enter the dive. He had problems engaging the flap as he was beginning his dive. While in the dive, he experienced normal compressibility problems because the flaps were not activated, and the violent thrusts sheared the tail off from the main structure. Kelsey was able to bail out and only sustained a broken ankle. The aircraft was totally destroyed. Another test P-38 would not be fitted with dive flaps for a few months.
Finally, another test P-38 was fitted with the dive flaps and testing was resumed. The Air Corps wanted Lockheed to test the aircraft with 2,000 lbs. of more weight and to start dives at 35,000 ft. The extra weight would cause additional acceleration of the aircraft during its dive, and would approach the critical Mach number sooner. This would be even more hazardous than before. Levier and Bircham resumed testing and would start at a 45-degree dive, and increase each test dive an additional 5-degree until they encountered problems. Levier was the first to encounter problem while using the dive flap. He was in a 60-degree dive, and began having problems when we reached 31,000 ft. The aircraft began to get away from him, even with the flaps deployed. Levier was fighting the aircraft to prevent it from tucking under itself as if it were in a regular dive. He decided to ride it out to see what would happen. He began his recovery at 20,000 ft., but he would not really begin to regain control until he was at 13,000 ft. The instruments registering the strain on the airframe were all over the 100% limit load. Bircham eased it back to the base without putting further stress on the aircraft. This was the evidence they needed to prove the flaps would hold up under an extreme dive, and not lead to disaster like many P-38s prior.”
And at least Ack-Ack agrees with me:
Originally posted by Ack-Ack
McGuire was famous for bring back planes with wings bent from stress and IIRC, it was common to see P-38s return home in such conditions.
Originally posted by Widewing
You know, if you keep posting nonsensical garbage,like the above, you are going to get reamed so much that you'll be able to pass a watermelon without so much as squinting... BOHICA!
Sorry, I’m straight. I am kind of flattered though.
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Originally posted by Viking
That would depend on the relative thickness of the tailplane vs. the wing.
Isn’t that what I said earlier that you protested against by calling it a “joke question”?
Certainly looks that way to me. :)
Actually i did call it a joke question, cause it is a major aspect NOT to prevent the plane to get into its critical mach.
A uptrimmed plane would remind the pilot, by raising the nose, not to get faster, but also offer forces where the pilot wouldnt be able to pull them.
With a uptrimmed plane you can dive faster, without to lose controll, thats my assumtion and thats what the 109 and 190 pilots did use, but they could trim even at highspeed.
btw, the relative thickness of the wing isnt a factor for the compression relatted downward movement, its the asymetrical airfoil, while the tailwing miss this.
And the compression related downward movement, that every plane with a asymetrical airfoil encounter(also the 262 and 163), dont have to do with shockwaves, which would damage the plane. The P38 tail got problems due to shockwaves comming from the middle fuselage, afaik the P47 dont got this problems.
Originally posted by Viking
The P-38s would often lose their tails in compressibility dives. Even while testing the new dive flaps the Lockheed test pilot lost the tail section of his P-38 and had to bail out. And even with the flaps extended the P-38 could suffer structural damage in dives. The P-38 was a fragile plane compared to most other fighters, often coming home with bent wings or tail sections after combat.
The question is at what speed did the P38 lose the tail??
Afaik the main problem remain the extreme dive acceleration of the P38. due to its smal wing surface in relation to its weight(high wingload), it had relative smal drag. This lead to high accelerations in dives.
The dive flaps keept the plane manouverable, but they didnt stop the plane to accelerate.
So the question is, at what mach did the tail fall appart??
I doubt this did happen very often in combat, at least not more often than a 109 dont got out of a dive, due to a frozzen trim system. I dont know many combat reports of lost P38´s due to dives. As long as the pilot did know the problem he always could prevent it, this of course is a handycap, on the other side the P38 and specialy the P47 had some very important advantages in high alt. ADVANCED POWER, SPEED, CLIMB and SERVICE CEILING.
This alone made them to very good escort planes, though the P38 had the known engine problems, what i consider as main problem for this plane in high altitude.
The 109A´s and 109G´s pilots maybe was happy to have their dive advantage, but in 7-8000m they had problems to get to the bombers at all, cause they had a big speed disadvantage(the few GM1 109´s are a exception, but they couldnt deal with the bombers anyway).
Although the P38´s wasnt able to follow a diving 109/190 for long time, they was able to protect the bombers, at least the was able to destroy the german attking formation, so the bombers was better able to protect themself!! Thats what history show, also here is not much to argue.
According to many combat reports the P47 driver dont got into bad trouble when he followed a german plane into a dive.
This is confirmed also by german pilots!!
Greetings,
Knegel
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Originally posted by Viking
From p-38online.com:
“After extensive testing, the answer to the problem was the use of a dive flap (or brakes). These flaps would be attached to the main spar under the wing. This would offset the loss in lift while in high-speed dives, and would allow the pilot to remain in control throughout the dive. Test pilots Tony Levier and Milo Bircham began a series of dive tests with the flaps. Lt. Benjamin Kelsey was sent by the Air Corps to evaluate the progress of the dive flaps. He took the modified P-38 and proceeded to enter the dive. He had problems engaging the flap as he was beginning his dive. While in the dive, he experienced normal compressibility problems because the flaps were not activated, and the violent thrusts sheared the tail off from the main structure. Kelsey was able to bail out and only sustained a broken ankle. The aircraft was totally destroyed. Another test P-38 would not be fitted with dive flaps for a few months.
Finally, another test P-38 was fitted with the dive flaps and testing was resumed. The Air Corps wanted Lockheed to test the aircraft with 2,000 lbs. of more weight and to start dives at 35,000 ft. The extra weight would cause additional acceleration of the aircraft during its dive, and would approach the critical Mach number sooner. This would be even more hazardous than before. Levier and Bircham resumed testing and would start at a 45-degree dive, and increase each test dive an additional 5-degree until they encountered problems. Levier was the first to encounter problem while using the dive flap. He was in a 60-degree dive, and began having problems when we reached 31,000 ft. The aircraft began to get away from him, even with the flaps deployed. Levier was fighting the aircraft to prevent it from tucking under itself as if it were in a regular dive. He decided to ride it out to see what would happen. He began his recovery at 20,000 ft., but he would not really begin to regain control until he was at 13,000 ft. The instruments registering the strain on the airframe were all over the 100% limit load. Bircham eased it back to the base without putting further stress on the aircraft. This was the evidence they needed to prove the flaps would hold up under an extreme dive, and not lead to disaster like many P-38s prior.”
LeVier validated the effectiveness of the flaps, with G loads up to 7.5 before Kelsey's flight. Kelsey in fact had never flown the P-38 in a critical mach dive before that flight. Even though the flaps had been extensively dive tested by LeVier, Beltz, Salmon, and Burcham, Kelsey wanted to see the results of deploying flaps after compressability was reached.
When he was already compressing, he tried to deploy the dive flaps to no effect, he tried again and broke the flap deployment handle off. His pratical inexpereince compressability, along with his decision to do this over the foothills of the Santa Monica Mountians (instead of over the ocean), lead him in desparation to apply full rudder, and full ailerons simultainiously while in a critical dive. That is when the **** hit the fan for the modified P-38G. The plane did not break up do to "normal" dive recoverly loads. It broke up due to pilot inexperience for those conditions.
Usually the individual's physical and mental limitations - not the plane's limitations - are factors that govern combat maneuverability. In many cases the plane will "take" a lot more than you as the pilot can stand; therefore, recognize your own limitations-know how many G's you can stand, and for how long; be so familiar with your plane that .you automatically react to a situation despite the gray haze that creeps before your eyes in a sharp pull out.
Ray Meskimen, Lockheed test pilot in a Lockheed publication
As you know, this (accelerated stall) can happen in sharp turns, pull-outs or other severe maneuvers. The '38 is designed to take the buffeting of the stall and has no tendency to fall off on either wing at any altitude. If combat necessitates, you can hold it in the accelerated stall as long as you can take the buffeting -- the ship will take it much longer.
Tony Levier, in another issue of the same publication
This "fragile" bird has been documented to shear off antenna masts, and a telephone poll with its wing, and survived the encounters to rtb.
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I don't think many would describe the P-38 as fragile. As with Mudr, there are cases I've read about where P-38's survived hitting telephone poles with a wing and in one case surviving a wingroot-to-wingroot headon collision with a Bf 109 in combat.
It did have its share of compressibility problems, but that is not the same as the plane being fragile.
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..................there is a fat "NOT" in one of the 1st sentences in my last post, that shouldnt be there!!
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Originally posted by Murdr
LeVier validated the effectiveness of the flaps, with G loads up to 7.5 before Kelsey's flight. Kelsey in fact had never flown the P-38 in a critical mach dive before that flight. Even though the flaps had been extensively dive tested by LeVier, Beltz, Salmon, and Burcham, Kelsey wanted to see the results of deploying flaps after compressability was reached.
It should also be noted that this P-38G was inspected after LeVier's dive and found to be undamaged by the prolonged exposure to at least 7.5 g.
Viking/GSholz is simply trolling to change topics after his outstanding demonstration of ignorance concerning the P-47. He's at the bottom of the hole and figures it's time to dig sideways.
I'm just gonna ignore him.
My regards,
Widewing
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Some thoughts: The size of the aircraft makes the limits of its sustainable Gs. A long wing acts as a better "leverage" than a shorter wing and thus it needs to be stronger and heavier if it is to withstand the same stress as a shorter wing.
The P38's engines and thus most weight is IN the wing and not in the center fuselage so the leverage point is somewhere in the inner part of the wing close to the engine.
That means also, e.g., that the TA152 cannot be pulled into as tight turn as the 190A or D without risking a wing failure.
Curious detail: The wing of the F8F was originally planned as "breakable" to allow it to make tighter high speed turns without risking overstressing the wings. The idea was later scrapped and it wasn't implemented to production machines. Dunno if this is actually true, though...
The slender booms of P38 are a potential place for oscillations to develop. Even Tiffie and Bf109 suffered for such effects. It is enough if certain engine revs vibrating the airframe find a sympathitetic vibration of airframe thus increasing it until the airframe starts to flutter and eventually fail. I think it is possible that some airframe could develop such behaviour without it necessarily being a specific feature of that particular type.
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In addition to the rest of "Viking's" falacies already addressed by Widewing and others, P-38's did not "often" lose their tails in compressibility, contrary to "Viking's" claim. As far as I know it happened a grand total of once, to Ralph Virden who was test flying an early model. He almost certainly tried to trim out of it, thus pulling too many gees once he reached denser air and ceased compressing.
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A note on what Murdr said about Kelsey - the P-38 normally recovered from compressibity at lower altitudes where the air was denser. It would begin to be controllable again at about fifteen thousand feet, and the pilot would be able to pull out with several thousand feet to spare. As Murdr said, however, Kelsey was over mountains. He was short several thousand feet, and knew this. He did not break up from compressibilty, he broke up from trying too hard to pull out early.
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Originally posted by Knegel
Actually i did call it a joke question, cause it is a major aspect NOT to prevent the plane to get into its critical mach.
A uptrimmed plane would remind the pilot, by raising the nose, not to get faster, but also offer forces where the pilot wouldnt be able to pull them.
I asked “What good would that do except perhaps preventing the plane from driving too fast by forcing the nose up?” because having the nose of your plane involuntarily raise out of control of the pilot does not help you catch and kill that German. Trimming the plane up would do nothing to make the plane a better diver, only prevent it from killing you. Of course if you fight it and enter a compressibility dive with the elevators trimmed up the plane is even more likely to kill you which is why P-47 pilots were ordered to trim neutral before diving.
Originally posted by Knegel
btw, the relative thickness of the wing isnt a factor for the compression relatted downward movement, its the asymetrical airfoil, while the tailwing miss this.
The relative thickness of the wing is the major determining factor of the wing’s critical Mach number. Only after the wing has reached its critical mach would the effects of asymmetric curvature be relevant. The relative thickness of the wing and tailplane determines which of the two first experience the effects of compressibility.
Originally posted by Murdr
When he was already compressing, he tried to deploy the dive flaps to no effect, he tried again and broke the flap deployment handle off. His pratical inexpereince compressability, along with his decision to do this over the foothills of the Santa Monica Mountians (instead of over the ocean), lead him in desparation to apply full rudder, and full ailerons simultainiously while in a critical dive. That is when the **** hit the fan for the modified P-38G
So you’re saying that the ailerons and rudders were still effective while in a compression dive? I doubt this very much; it is aerodynamically impossible. More likely that Knegel is right that supersonic shockwaves were the culprit.
Originally posted by Murdr
This "fragile" bird has been documented to shear off antenna masts, and a telephone poll with its wing, and survived the encounters to rtb.
It was a big and heavy plane that could withstand a good deal of damage, but its size and weight was also a liability since the P-38 was limited to 6 G’s. The Spitfire, 109 and 190 had a full one third higher G-limit. At 8 G’s the Spitfire wouldn’t even over-G, but the P-38 would start falling apart. Widewing indirectly confirmed this (much to his annoyance I can imagine) when he stated:
Originally posted by Widewing
Typically, American fighers were rated about 2 G below failure loading. Except that is, Grumman aircraft which repeated demonstrated the ability to survive tremendous loads without failure.
It was fragile.
Originally posted by Widewing
I'm just gonna ignore him.
Yes of course you will skulk away like you did last time. I expected nothing more from you.
Originally posted by Benny Moore
He did not break up from compressibilty, he broke up from trying too hard to pull out early.
The tail was sheared off while he was still in a compressibility dive. You show a complete lack of understanding the effects of compressibility if you think he managed to pull any G’s at all.
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Ignore him guys... He's still fishing in the dead sea.
My regards,
Widewing
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Evade all you want Corey, but it won’t change the fact that YOU wrote this:
“Gradually, the Group learned how to manage the Thunderbolt. Still, there was a new problem beginning to appear. Powerful fighters such as the P-47 and P-38 were encountering something relatively new to aviation; compressibility. This new generation of high-speed aircraft were capable of incredible speeds in a dive. Compressibility is a term used to describe what happens when localized airflow across a wing approaches transonic velocity. The resulting shock wave could lock the elevators as if in a vise. Pilots were running up against compressibility and they were dying. P-47’s and P-38’s were being flown straight into the ground, or even breaking up in flight.”
Infuriating isn’t it? How can you be so anti-American?! :lol
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Clearly P-38 and P-47 suffered so from this all-American phenomenon.
Incidentally, to those wondering, it is possible to have only one control surface locked up in a compressibilty dive. Much like in a stall, airflow does not affect all control surfaces equally. The P-38's problem was elevator; trans-sonic shockwaves immobilized it. Trim could overcome it (at risk of breaking up, as did Virden), although under some conditions the wing might not have lift even at very high speed.
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Originally posted by Viking
So you’re saying that the ailerons and rudders were still effective while in a compression dive? I doubt this very much; it is aerodynamically impossible. More likely that Knegel is right that supersonic shockwaves were the culprit.
I related what Kelsey's AAR of the event was. He input full ailerons and rudders, something immediately broke on the plane, and he found himself in an inverted flat spin, and was stuck there momentarily with the canopy pinned shut until G force direction changed and pitched him out of the cockpit.
If you didn't want further details from the incident, I guess you shouldn't have brought it up.
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Originally posted by Viking
I asked “What good would that do except perhaps preventing the plane from driving too fast by forcing the nose up?” because having the nose of your plane involuntarily raise out of control of the pilot does not help you catch and kill that German. Trimming the plane up would do nothing to make the plane a better diver, only prevent it from killing you. Of course if you fight it and enter a compressibility dive with the elevators trimmed up the plane is even more likely to kill you which is why P-47 pilots were ordered to trim neutral before diving.
You realy think they shot each other down at mach 0,73 in 1943?? The 109´s got stiff even more early, there was nothing to fear at this speed than the speed.
Originally posted by Viking
The relative thickness of the wing is the major determining factor of the wing’s critical Mach number. Only after the wing has reached its critical mach would the effects of asymmetric curvature be relevant. The relative thickness of the wing and tailplane determines which of the two first experience the effects of compressibility.
The its not only the relative thickness, the aspecratio and airfoil is a majorfactor here. But as i wrote before, the main wing in general had a greater relative thickness anyway, as result the planes started to tuck down before they got absolutly stiff, a uptrimmed plane or a early reaction of the pilot would stop the plane to get into the real stiffness. But in general the P47´s could get recovered in lower alts anyway, in general they didnt felt appart.
Originally posted by Viking
So you’re saying that the ailerons and rudders were still effective while in a compression dive? I doubt this very much; it is aerodynamically impossible. More likely that Knegel is right that supersonic shockwaves were the culprit.
Nowhere i wrote that shockwaves ripped off the tail, the shockwaves made the P38 stiff and i wrote that even the P38 normaly could get recovered in lower alts!!
Originally posted by Viking
It was a big and heavy plane that could withstand a good deal of damage, but its size and weight was also a liability since the P-38 was limited to 6 G’s. The Spitfire, 109 and 190 had a full one third higher G-limit. At 8 G’s the Spitfire wouldn’t even over-G, but the P-38 would start falling apart. Widewing indirectly confirmed this (much to his annoyance I can imagine) when he stated:
It was fragile.
I would say the results in war show that it wasnt fragile, but of course fragile is relative!
The P38 was very successfull in the war and you dont will find many combat reports where it crashed due to structural limits. In my book fragile is a plane that get damaged dangerus easy, while normal combat flight manouvers. The P38 was not in this class.
Originally posted by Viking
The tail was sheared off while he was still in a compressibility dive. You show a complete lack of understanding the effects of compressibility if you think he managed to pull any G’s at all.
How you know this? At what alt the plane felt appart?? Below 5000m every WWII piston engined plane with reduced power has problems to stay inside its critical mach. The assumption the pilot had to overstress the plane, cause he was over hills, is rather logical.
Also the 109´s got damaged then(some ripped off their wings cause the trimsystem didnt work smooth, cause it froze).
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What seems to elude our friend is that every modern fighter (by mid 1940s standards) suffered from compressibility. Germans died, Russians died, Brits died and Americans died due to diving too fast and having little to no experience on how to recover. I have a photo of a P-40E a split second before it crashed into the ground in a full compressibility dive. There's many accounts of Bf 109 and Fw 190 pilots dying when they failed to extricate their fighters from a dive while being pursued by P-47s. I know of similar incidents with the F6F and F4U. It was a problem common to all high performance fighters, regardless of manufacturer. The fact that this seems to escape certain people is deliberate....
What amazes me is that despite being dragged over the coals for gross inaccuracies, our friend plods along oblivious to the fact that he no longer has any credibility. Things like the comment, "The P-47M had a completely redesigned semi-laminar flow wing that had a much higher critical Mach than earlier P-47 wings." is complete nonsense. Pure balderdash. When asked for a citation... Silence.
Now, let's see if he can produce a technical document that shows that the P-38 was "fragile". He won't, because no such document exists. On the contrary, test pilot reports say just the opposite. All you have to do is read LeVier's book to see this.
What he will do is search the internet, copy, cut and paste from what he finds regardless of the context to support his argument. Not one iota of technical data has been offered. Just opinion or material extracted from its context. When cornered (as he has been from the outset), he'll attempt a strawman argument or try to change the focus of the debate, as if this were not readily transparent. If nothing else works, he'll merely conjure up something from thin air (like that "semi-laminar flow wing" thing he invented previously).
I'd rather not waste my time responding to trolling. He's lost every argument that he's started and I don't see him suddenly getting smart. Nonetheless, that won't shut him up, will it?
My regards,
Widewing
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stop feeding the troll :p
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Originally posted by Benny Moore
Clearly P-38 and P-47 suffered so from this all-American phenomenon.
I’m sure you can get an ointment to help relieve that bruised national pride of yours. The P-38 and P-47 did suffer from compressibility effects, and so do every other plane. However several other fighters, including American, were better suited to deal with the effects. The Spitfire had the highest critical Mach number of any WWII piston-engine fighter, much higher than the P-38 and P-47. The 109 and 190 both had higher critical Mach (but not by as much as the Spit) and a “flying-tail” trim system that allowed them to trim out of dives. The P-51’s laminar-flow wing and high critical Mach number made it an excellent diver.
Originally posted by Benny Moore
Incidentally, to those wondering, it is possible to have only one control surface locked up in a compressibilty dive. Much like in a stall, airflow does not affect all control surfaces equally. The P-38's problem was elevator; trans-sonic shockwaves immobilized it. Trim could overcome it (at risk of breaking up, as did Virden), although under some conditions the wing might not have lift even at very high speed.
Again you show little knowledge of the effects of compressibility and local supersonic airflow. When the airflow gets close to transonic speeds the leading edge of a thick wing (like those found on WWII fighters) acts almost as a snow-plow deflecting the air away from the wing and disrupting the normal flow of air over the wing.
(http://www.onpoi.net/ah/pics/users/1022_1178665902_compeff.gif)
Behind the shock wave the air flow is turbulent, including the boundary layer, and thus renders conventional control surfaces ineffective. The turbulent air flow can cause the control surfaces to vibrate or even oscillate between its extremes of deflection like the ailerons on the P-47 and 109. However, the important fact is that since conventional ailerons and elevators work by changing the curvature of the whole airfoil (wing) they don’t work when the airflow is separated and turbulent. For all intents and purposes the wing is stalled behind the region where the shock impinges on the surface of the wing. You can move the control surfaces to their maximum deflection and they will do nothing. On some planes the controls become lighter after the wing airflow enters compressibility, still the controls remain ineffective.
Originally posted by Murdr
I related what Kelsey's AAR of the event was. He input full ailerons and rudders, something immediately broke on the plane, and he found himself in an inverted flat spin, and was stuck there momentarily with the canopy pinned shut until G force direction changed and pitched him out of the cockpit.
If you didn't want further details from the incident, I guess you shouldn't have brought it up.
If you have this AAR I’d appreciate if you could post it in its entirety. Right now we have one source that says the tail was sheared off by compressibility effects, two guys that assume and speculate that the pilot simply pulled too many G’s pulling out of the dive, and you that say the pilot broke the plane by applying full rudder and ailerons.
Originally posted by Knegel
You realy think they shot each other down at mach 0,73 in 1943?? The 109´s got stiff even more early, there was nothing to fear at this speed than the speed.
At Mach 0.73 there was nothing to be afraid of in a Spitfire, 109 or several other fighters. The controls were heavy in the 109 yes, but not beyond what a normal man could pull with two hands. Like I’ve explained to Benny above the problem with compressibility effects is not that controls get heavy, it’s that the controls become ineffective regardless of control input. The 109 would only be trying to get away from the P-47; the P-47 was the plane that was trying to shoot. To answer your question: no I do not think they shot each other down at Mach 0.73 in 1943. Not often anyway. The shoot-downs would occur at significantly lower speeds where a higher P-47 uses its great mass and HP to out accelerate the 109 and catch it before speed increased too much.
Originally posted by Knegel
The its not only the relative thickness, the aspecratio and airfoil is a majorfactor here. But as i wrote before, the main wing in general had a greater relative thickness anyway, as result the planes started to tuck down before they got absolutly stiff, a uptrimmed plane or a early reaction of the pilot would stop the plane to get into the real stiffness.
Aspect ratio and airfoil are very minor factors in determining the speed at which the effects of compressibility start. However airfoil is a major factor in the severity and nature of the compressibility effects. And again you speak about “stiffness” … as I’ve explained above the problem was not “stiffness”, and now your argument has turned into a “just don’t fly that fast” solution to the P-47’s dive problems.
Originally posted by Knegel
Nowhere i wrote that shockwaves ripped off the tail, the shockwaves made the P38 stiff and i wrote that even the P38 normaly could get recovered in lower alts!!
My mistake, I misread you.
Originally posted by Knegel
I would say the results in war show that it wasnt fragile, but of course fragile is relative!
The P38 was very successfull in the war and you dont will find many combat reports where it crashed due to structural limits. In my book fragile is a plane that get damaged dangerus easy, while normal combat flight manouvers. The P38 was not in this class.
I agree that “fragile” is a relative and subjective term. However I do agree with NASA’s point of view (from NASA Facts):
“The need for transonic research airplanes grew out of two conditions that existed in the early 1940s. One was the absence of accurate wind tunnel data for the speed range from roughly Mach 0.8 to 1.2. The other was the fact that fighter aircraft like the P-38 "Lightning" were approaching these speeds in dives and breaking apart from the effects of compressibility—increased density and disturbed airflow as the speed approached that of sound, creating shock waves.”
Also from p-38online:
“A typical dive of the P-38 from high altitudes would always experience compressibility. Starting from 36,000 ft., the P-38 would rapidly approach the Mach .675 (445 mph true airspeed). At this point, the airflow going over the wing exceeds Mach 1. A shockwave is created, thus breaking up the airflow equaling a loss of lift. The shockwave destroys the pressure difference between the upper and lower wing, and disrupts the ability for the aircraft to sustain flight. As the lift decreases, the airflow moving back from the wing also changes in its form and pattern. Normal downwash aft of the wing towards the tail begins to deteriorate. The airflow across the tail shifts from normal to a condition where there is now a greater upload, of lifting force, on the tail itself. With the greater uploading force applied to the tail, the nose of the aircraft wants to nose down even more, which creates a steeper and faster dive. As the aircraft approaches the vertical line, it begins to tuck under and starts a high-speed outside loop. At this point, the airframe is at the greatest point of structural failure. When the angle of attack increases during the dive, it also increases for the tail. The resulting effect is that the pilot cannot move the controls because tremendous force is required to operate the aircraft. The pilot is simply a passenger during this period. Shockwaves become shock fronts, which decrease the lift no matter what the pilot tries to do. Instead of smooth airflow over the wing, it is extremely turbulent, and strikes the tail with great force. The aircraft can only recover when it enters lower, denser atmosphere lower to the ground.
The solution to the problem was in understanding that the speed of sound changes with the altitude. At sea level, it is 764 mph, while at 36,000 ft. it is 660 mph. An aircraft moving at 540 mph at 36,000 ft. is much higher in the compressibility zone. The same speed at sea level results in the aircraft being exposed to lower effects of compressibility, and will respond to pilot controls. The dive recovery flap was a solution to this problem. In the ETO, German pilots would dive out of trouble because they knew the P-38 pilots would not follow. This greatly reduced the effectiveness of the aircraft in normal battle conditions. The NACA tested the flaps in high-speed wind tunnels at the Ames Laboratory. They tried several locations before discovering that when the flaps were positioned just aft of the trailing edge of the wings, it showed definite improvements. The flaps were finally positioned beneath the wings outboard of the booms, and just aft of the main structural beam. The pilots had a button on the yoke, and would simply activate the flap just prior to entering a dive.”
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Originally posted by Knegel
How you know this? At what alt the plane felt appart?? Below 5000m every WWII piston engined plane with reduced power has problems to stay inside its critical mach. The assumption the pilot had to overstress the plane, cause he was over hills, is rather logical.
Me not knowing the altitude does not mean it didn’t happen. I only know what the document from p-38online.com stated:
“After extensive testing, the answer to the problem was the use of a dive flap (or brakes). These flaps would be attached to the main spar under the wing. This would offset the loss in lift while in high-speed dives, and would allow the pilot to remain in control throughout the dive. Test pilots Tony Levier and Milo Bircham began a series of dive tests with the flaps. Lt. Benjamin Kelsey was sent by the Air Corps to evaluate the progress of the dive flaps. He took the modified P-38 and proceeded to enter the dive. He had problems engaging the flap as he was beginning his dive. While in the dive, he experienced normal compressibility problems because the flaps were not activated, and the violent thrusts sheared the tail off from the main structure. Kelsey was able to bail out and only sustained a broken ankle. The aircraft was totally destroyed. Another test P-38 would not be fitted with dive flaps for a few months.”
It does not mention anything about pilot control inputs or over-G during pull-out. It simply states that while in the dive he experienced compressibility effects and that the “violent thrusts” sheared the tail off. You may make assumptions to the contrary to your heart’s content, but it won’t change what was written.
Originally posted by Widewing
What seems to elude our friend is that every modern fighter (by mid 1940s standards) suffered from compressibility. Germans died, Russians died, Brits died and Americans died due to diving too fast and having little to no experience on how to recover. [snip] The fact that this seems to escape certain people is deliberate....
Nice switch Corey, you and others in this thread are arguing that the P-47 and P-38 did not. I am not the person religiously defending his favorite planes here. I know 109 and 190 pilots fell to their deaths just like their American opponents, and I have never said anything to the contrary. If you think I have then please quote me, the forum’s search function is at your disposal.
Originally posted by Widewing
What amazes me is that despite being dragged over the coals for gross inaccuracies, our friend plods along oblivious to the fact that he no longer has any credibility. Things like the comment, "The P-47M had a completely redesigned semi-laminar flow wing that had a much higher critical Mach than earlier P-47 wings." is complete nonsense. Pure balderdash. When asked for a citation... Silence.
I was wrong about the P-47M having a laminar-flow wing. I must have misread that somewhere. However the XP-47F did have a laminar-flow wing. Ironically it too crashed.
Originally posted by Widewing
What he will do is search the internet, copy, cut and paste from what he finds regardless of the context to support his argument. Not one iota of technical data has been offered. Just opinion or material extracted from its context.
Actually I’ve presented the opinions and material from people infinitely your superior in the matter at hand. Your word is insignificant by comparison.
Originally posted by Widewing
I'd rather not waste my time responding to trolling. He's lost every argument that he's started and I don't see him suddenly getting smart. Nonetheless, that won't shut him up, will it?
Again with the insults, and calling me a troll is rather ironic. I may be mistaken about certain things … many things even … but at least I have not shown myself to be such a disrespecting zealot that resorts to name calling against people infinitely your superior.
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Guys, it's the internet.
You're coming off as one that can't sleep until their argument is won. Which we all know on the internet is impossible no matter what evidence and annecdotes are produced.
BTW, my vote's for the P-47 beating the 190. But that's not based on scientific data, just my humble opinion. Either way it doesn't matter which one would actually win; it's just a game in a make believe world.
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Originally posted by Viking
. The recovery procedure developed for the P-47 reflects this; before diving the trim was to be set to neutral.
P-47 POH states that the aircraft shall be trimmed tail heavy before a dive to reduce the pressures necessary for pullout.
Nice switch Corey, you and others in this thread are arguing that the P-47 and P-38 did not. I am not the person religiously defending his favorite planes here. I know 109 and 190 pilots fell to their deaths just like their American opponents, and I have never said anything to the contrary. If you think I have then please quote me, the forum’s search function is at your disposal.
I think the original genesis of the argument was your tenacity in defending Brown's stated .73 critical mach of the P-47, a speed that is only defended by one source, and contradicted by many others.
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Originally posted by Viking
Right now we have one source that says the tail was sheared off by compressibility effects, two guys that assume and speculate that the pilot simply pulled too many G’s pulling out of the dive, and you that say the pilot broke the plane by applying full rudder and ailerons.
Bibliography for p-38online
Bodie, Warren M. The Lockheed P-38 Lightning. Widewing Publications, Georgia. 1991.
Caidin, Martin. Fork-Tailed Devil: The P-38. iBooks, Icn. New York. 1971, 2001.
Davis, Larry. P-38 Lightning in Action #109. Squadron/Signal Publications, Inc, Texas. 1990.
O'Leary, Michael. Thunderbolt and Lightning. Osprey Publishing, London. 1996.
Stanaway, John. Peter Three Eight, The Pilots Story. Pictorial Histories Publishing Company, Missoula, Montana. 1986.
Source that I paraphrased: Bodie, Warren M. The Lockheed P-38 Lightning. Widewing Publications, Georgia. 1991
Bodies sources, among many, were Kelly Johnson (who wrote the forward), Gen Ben Kelsey, Tonly LeVier, Arthur Heiden...actually the acknowledgements are two full pages. I guess if a former Lockheed engineer/supervisor who had first hand access to internal documents and people isn't a good enough source, nothing is.
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Nothing that does not discredit the P-38 is a good enough source for GScholz.
By the way Benny, Virden did NOT compress. Kelly Johnson said he was pretty sure a trim tab on the elevator broke, and allowed the elevator to move too far and he felt the P-38 reached well over 12G before the tail snapped. Virden was already out of the dive and flying level at high speed after the pullout. The test wasn't even a regular sanctioned dive test.
You aren't helping your argument by using McGuire bending P-38's as an example, GScholz. Most of McGuire's squadron, and his crew, figure McGuire was exceeding 9G on a regular basis. the guys in his squad couldn't follow him,. and would not have if they could. Your premise that P-38's were fragile is completely baseless. No one is surprised by that though.
If you REALLY check into the reports real well, you'll find that MOST of the planes, ESPECIALLY P-38's and P-47's, that were lost in terminal dives were lost when inexperienced pilots decided to "see what happened" if you exceeded the placarded speeds and angles.
And GScholz, if you REALLY want to learn about the P-38, try reading Bodie's book, as opposed to a P-38 website.
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Originally posted by Captain Virgil Hilts
Nothing that does not discredit the P-38 is a good enough source for GScholz.
Actually I was being sarcastic since he seemed to be giving equal weight to 4th hand interpretations "two guys that assume and speculate that the pilot simply pulled too many G’s pulling out of the dive", 3rd hand interpretation (a website publisher that was somewhat obligated to substantially reword his sources), and two of us simply paraphrasing the same source.
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Originally posted by Viking
At Mach 0.73 there was nothing to be afraid of in a Spitfire, 109 or several other fighters. The controls were heavy in the 109 yes, but not beyond what a normal man could pull with two hands. Like I’ve explained to Benny above the problem with compressibility effects is not that controls get heavy, it’s that the controls become ineffective regardless of control input. The 109 would only be trying to get away from the P-47; the P-47 was the plane that was trying to shoot. To answer your question: no I do not think they shot each other down at Mach 0.73 in 1943. Not often anyway. The shoot-downs would occur at significantly lower speeds where a higher P-47 uses its great mass and HP to out accelerate the 109 and catch it before speed increased too much.
Aspect ratio and airfoil are very minor factors in determining the speed at which the effects of compressibility start. However airfoil is a major factor in the severity and nature of the compressibility effects. And again you speak about “stiffness” … as I’ve explained above the problem was not “stiffness”, and now your argument has turned into a “just don’t fly that fast” solution to the P-47’s dive problems.
Hi,
The controlls not always get ineffective, they turn to work in the oposide way, while the elevator in general remain effective for a longer time, but the stickvariations and therefor forces, to counter the beginning "tuck down" was to be to much!
Afaik the main ptoblem for the P38 was early shockwaves around the middle fuselage section(very high relative thickness), which did hit the tailwing and did lead to the rather early loss of manouverability. This in combination with the extreme acceleration did need a experienced pilot, similar like in the german jets, but at a lower speed. This dont make the plane not combat worthy as a escor plane. The escort planes dont had to follow the enemy down, they had to stay high anyway to drag other enemys away and thats what the P38´s did rather successfull, despite their ugly engine problems in cold air.
Aspectratio is a major aspect for compressibility and airfoil as well!!
Most planes with +1mach speed have a very smal aspectratio! This is so, cause while compressibility appear, the airmasses need to get shifted sideard to the wingtip. A smal aspectratio can do this better than a high aspectratio wing.
A high lift airfoil(extreme asymetic) will have the "tuck down" much more than a symetrical airfoil. And the laminar airfoil also work better than a high lift airfoil.
It dont matter why a plane get stiff, it only matter than the pilot cant fight under this conditions. The Me109 got stiff around the roll axe good below compressibility did happen.
And actually i dont wanna say the P47 had a higher critical mach, i only wanna say that the RAE conclusions got proven as wrong!!
The RAE also fount to be the Hurri a better fighter than the 109 and their conclusion was the 109 was obsolete in 1943.
Originally posted by Viking
I agree that “fragile” is a relative and subjective term. However I do agree with NASA’s point of view (from NASA Facts):
“The need for transonic research airplanes grew out of two conditions that existed in the early 1940s. One was the absence of accurate wind tunnel data for the speed range from roughly Mach 0.8 to 1.2. The other was the fact that fighter aircraft like the P-38 "Lightning" were approaching these speeds in dives and breaking apart from the effects of compressibility—increased density and disturbed airflow as the speed approached that of sound, creating shock waves.”
Nothing special here, the 109 and FW190 also was planes like the P38. The different to other planes was: They was by easy able to reach +mach 0,75.
I remember a story of a finnish pilot, who couldnt understand why someone create a plane, that can dive so fast without to make it strong enough and manouverable enough and he was talking about the 109 after a +700km/h IAS dive.
The germans also worked on better airfoils and specialy wingforms(shifted wing and/or extreme smal wing aspectratio in the 262, 163 and he162) cause they did encounter exact the same problems, maybe a bit later and with a less fast acceleration, so more time to react.
Originally posted by Viking
Also from p-38online:
“A typical dive of the P-38 from high altitudes would always experience compressibility. Starting from 36,000 ft., the P-38 would rapidly approach the Mach .675 (445 mph true airspeed). At this point, the airflow going over the wing exceeds Mach 1. A shockwave is created, thus breaking up the airflow equaling a loss of lift. The shockwave destroys the pressure difference between the upper and lower wing, and disrupts the ability for the aircraft to sustain flight. As the lift decreases, the airflow moving back from the wing also changes in its form and pattern. Normal downwash aft of the wing towards the tail begins to deteriorate. The airflow across the tail shifts from normal to a condition where there is now a greater upload, of lifting force, on the tail itself. With the greater uploading force applied to the tail, the nose of the aircraft wants to nose down even more, which creates a steeper and faster dive. As the aircraft approaches the vertical line, it begins to tuck under and starts a high-speed outside loop. At this point, the airframe is at the greatest point of structural failure. When the angle of attack increases during the dive, it also increases for the tail. The resulting effect is that the pilot cannot move the controls because tremendous force is required to operate the aircraft. The pilot is simply a passenger during this period. Shockwaves become shock fronts, which decrease the lift no matter what the pilot tries to do. Instead of smooth airflow over the wing, it is extremely turbulent, and strikes the tail with great force. The aircraft can only recover when it enters lower, denser atmosphere lower to the ground.
This is well known, but the interesting thing is that the P38 in the vertical dive have a much greater mach than 0,7, probably rather mach 0,85, and although its not manouverable anymore, it generally dont break appart.
Originally posted by Viking
The solution to the problem was in understanding that the speed of sound changes with the altitude. At sea level, it is 764 mph, while at 36,000 ft. it is 660 mph. An aircraft moving at 540 mph at 36,000 ft. is much higher in the compressibility zone. The same speed at sea level results in the aircraft being exposed to lower effects of compressibility, and will respond to pilot controls. The dive recovery flap was a solution to this problem. In the ETO, German pilots would dive out of trouble because they knew the P-38 pilots would not follow. This greatly reduced the effectiveness of the aircraft in normal battle conditions. The NACA tested the flaps in high-speed wind tunnels at the Ames Laboratory. They tried several locations before discovering that when the flaps were positioned just aft of the trailing edge of the wings, it showed definite improvements. The flaps were finally positioned beneath the wings outboard of the booms, and just aft of the main structural beam. The pilots had a button on the yoke, and would simply activate the flap just prior to entering a dive.”
Yes, the different mach with different temperature is known, intersting is, 36000ft is roundabout the service ceiling of the 109G and 190A in 1943 and while a escort mission the planes rarely did fly above 30000ft.
My conclusion still remain:
The P47C/D was a very good high alt fighter in 1943, the problem of a relative low critical mach number was nothing special and was only one (not very) weak point, otherwise it did outperform the 109G and specialy 190A in 30k by easy.
The P38 wasnt that good in high alt in 1943, but mainly due to the engine problems, not cause the low critical mach, which still is good above the Vmax. History show, it was still good enough as a escort plane, to drag the enemy away, while its engine problems and extreme mach limitation dont made it to an air superiority fighter in this altitude(at least not in europe) in 1943.
Greetings,
Knegel
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Originally posted by Knegel
And actually i dont wanna say the P47 had a higher critical mach, i only wanna say that the RAE conclusions got proven as wrong!!
Perhaps you should stop shouting and instead actually read the RAE reports and also the article on the Republic tests. The phenomena is described exactly same in the both cases; heavy and uneffective elevaror control, uneffective trim, buffeting etc. The only (minor) difference between the results is about 0,03-0,05 unit difference in the measured Mach numbers which is probably caused by measurement errors. The RAE results are probably more accurate because they were doing quite a lot high speed research that time.
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The spitfire had the highest mach number, but was widely considered as a poor diver compared to its contemporaries. What does that mean?
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It means that its wing, as big as it is, is relatively thin but compared to weight of the a/c the drag is rather big too. So the Spit can be flown quite safely in high speed without compression effects but the problem is to get into those speeds. I guess that Spit is rather slow to reach its critical mach. More weight would have helped but that is a trade off.
Spit has inner NACA 2213, outer NACA 2209.4 profiles, compare it to thicker wing of FW190 with inner NACA 23015.3, and outer NACA 23009. So the Spit's wing thickness is 13% of the profile chord and FW has 15% meaning that FW profile reaches the compression earlier, although the wing sweep delays this some.
-C+
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Also remember when considering the compression effects that the rules that apply to main wing do not apply to elevator as elevator has different profile and it generally compresses later than the main wing and its hinge configuration and other factors determine how "set in concrete" it becomes in high speed dives.
-C+
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Originally posted by gripen
The RAE results are probably more accurate because they were doing quite a lot high speed research that time.
So the flight test results (using planes that were instrumented to test exactly how compressibility affected them) that occurred later in the war (or after) are less accurate than tests conducted using production aircraft on loan from 8th AF?
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Originally posted by Stoney74
So the flight test results (using planes that were instrumented to test exactly how compressibility affected them) that occurred later in the war (or after) are less accurate than tests conducted using production aircraft on loan from 8th AF?
I don't think that there is somekind of accurate/exact/final truth on this kind of issue. It can be said that at least in the tested configuration (both tests, RAE and Republic) the P-47 had some undesirable characters at high mach numbers. Anyway, they certainly had a good reason to add the dive recovery flaps.
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lol Charge, you missed my point. I know all too well what compression and shockwaves are.
My point was that whatever mach limit was for the spit it didn't make it a great diver in combat. The argument about the precision in the measurements of diving mach number is meaningless in terms of real life tactical opperations. P47 held through compression good enough and accelerated fast enough after the diving 109s, that by the time those few percent did make a difference, the 109 was already torn by 8*0.5s... and same goes for the 190s.
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Originally posted by gripen
Perhaps you should stop shouting and instead actually read the RAE reports and also the article on the Republic tests. The phenomena is described exactly same in the both cases; heavy and uneffective elevaror control, uneffective trim, buffeting etc. The only (minor) difference between the results is about 0,03-0,05 unit difference in the measured Mach numbers which is probably caused by measurement errors. The RAE results are probably more accurate because they were doing quite a lot high speed research that time.
Perhaps you should read before writing??
I dont wrote the RAE datas are wrong, but their (Browns) conclusion the P47 is useless as a high alt fighter.
This conclusion got proven as wrong(by history), not the datas.
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Originally posted by Knegel
..their (Browns) conclusion the P47 is useless as a high alt fighter.
This conclusion got proven as wrong(by history), not the datas.
Your reply is a perfect example of a straw man argument. (Except if you can prove the "useless as a high alt fighter" -quote.)
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Originally posted by TimRas
Your reply is a perfect example of a straw man argument. (Except if you can prove the "useless as a high alt fighter" -quote.)
I think you misread what Knegel was trying to say.
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Originally posted by TimRas
Your reply is a perfect example of a straw man argument. (Except if you can prove the "useless as a high alt fighter" -quote.)
Reread the theatre, Viking did quote Eric Braun(testpilot of the RAE), where he found the P47 to be useless in high alt.
If Brown didnt say this and if noone else in the RAE is/was this opinion, Vikings complete argumentation miss any base.
Greetings,
Knegel
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Originally posted by Knegel
Perhaps you should read before writing??
I dont wrote the RAE datas are wrong, but their (Browns) conclusion the P47 is useless as a high alt fighter.
This conclusion got proven as wrong(by history), not the datas.
Let's quote your (shouting) posting from above:
"And actually i dont wanna say the P47 had a higher critical mach, i only wanna say that the RAE conclusions got proven as wrong!!
The RAE also fount to be the Hurri a better fighter than the 109 and their conclusion was the 109 was obsolete in 1943."
There is nothing about Brown and infact you add more arguments against RAE.
The history part is that P-47 was mostly doing ground attack tasks in the ETO once there were enough P-51s.
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You still dont seems to understand that i dont dont say anything against the testdatas. Same like the other heavy and powerfull planes, the P47 got into speeds where compressions occur and it may be the P47 had a rather low tactical critical mach, i never told something different.
This whole discussion started cause someone used the RAE datas in combination with Eric Browns(RAE testpilot) statement as argument against the P47´s high alt qualitys, despite even the germans found the P47 to be a pretty good plane, specialy in the dive!!
Here is what Viking wrote again: "RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k."
So it sounds to me the RAE had this conclusion, at least Brown, who did work for the RAE had this conclusion(according to Viking).
Actually its not realy important who had this conlusion, its important that history proof this conclusion as wrong and so its not a valid argument.
In 1943/44 the P47C/D was a good high alt fighter in comparison to its common oponents, the P47C/D didnt felt appart when it got into speeds above its tactical critical mach and the P47C/D in general dont got into a death trap, if it got above its critical tactical mach.
The P47 made mostly ground attacks not cause it was bad in high alt, rather cause the P51 was not that good in low alt(couldnt take much groundfire and couldnt carry as much loadout) and cause the P51 simply was a better fighter in general.
Nevertheless the P47 made a very good job in 1943 and early 44 in high alt, the only bad limitaion was the short range of the early models, not the low critical mach. When the P47 dissapeared from the escort role, the LW already was pretty much down.
If the hint, the P47 got used most in low level, was meant as an argument against its high alt qualitys, also the Ta152H must have been a bad high alt fighter, cause it ONLY got used in low/medium level. :rofl
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Originally posted by Knegel
You still dont seems to understand that i dont dont say anything against the testdatas.
Well, I do understand when you shout that "the RAE conclusions got proven as wrong!!".
Originally posted by Knegel
So it sounds to me the RAE had this conclusion, at least Brown, who did work for the RAE had this conclusion(according to Viking).
That is your poor iterpration (and probably also Viking's); generally people have opinions but that does not mean that opinion of a person presents opinion of the organisation where he/she works (has worked).
Besides, presenting an opinion (founded or not) does not justify public name calling seen in this thread nor bashing of the organisation.
Originally posted by Knegel
Actually its not realy important who had this conlusion, its important that history proof this conclusion as wrong and so its not a valid argument.
Well, the true history is that the P-47 got the dive recovery flaps. Certainly for a good reason.
Originally posted by Knegel
In 1943/44 the P47C/D was a good high alt fighter in comparison to its common oponents, the P47C/D didnt felt appart when it got into speeds above its tactical critical mach and the P47C/D in general dont got into a death trap, if it got above its critical tactical mach.
RAE and Republic data is quite clear on this; the pilot was more or less a passenger at high mach numbers.
Originally posted by Knegel
Nevertheless the P47 made a very good job in 1943 and early 44 in high alt, the only bad limitaion was the short range of the early models, not the low critical mach. When the P47 dissapeared from the escort role, the LW already was pretty much down.
The P-47 was a good performer at altitude and the critical mach number difference is small if compared to German fighters (couple %). But that does not mean that there was no compressibility related problems; 8th AF certainly had a reason to sent a P-47 to the RAE for the tests.
Originally posted by Knegel
...even the germans found the P47 to be a pretty good plane, specialy in the dive!!
The dive acceleration is not the same thing as the critical mach number and other compressibility related issues.
BTW there is no reason to shout all the time.
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Originally posted by gripen
Well, I do understand when you shout that "the RAE conclusions got proven as wrong!!".
You clearly dont! Cause like so often you take smal things out of the whole contex!
Originally posted by gripen
That is your poor iterpration (and probably also Viking's); generally people have opinions but that does not mean that opinion of a person presents opinion of the organisation where he/she works (has worked).
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The datas in combination with Browns statement, who was a member of the RAE, simply came around like its the RAE conclusion. But as i wrote, its not important here, important is that its wrong.
Originally posted by gripen
Besides, presenting an opinion (founded or not) does not justify public name calling seen in this thread nor bashing of the organisation.
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I didnt bash the RAE, i only wrote they was wrong before, with their conclusions. Conclusions out of datas, to be used in future often are wrong, i did offer the Hurri/109 example to show this, not to bash the RAE in general.
If the RAE dont had Browns opinion, someone of them should clarify this, cause Brown is probably the best known member of the RAE and his words always will stay tight with the RAE.
Originally posted by gripen
Well, the true history is that the P-47 got the dive recovery flaps. Certainly for a good reason.
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What have this to do with the statement "the P47 was useless as high alt fighter"??
btw, the true history is, the dive recovery flaps rarely got used in war and the P47 did perform good without this flaps.
True history is, at a time when no mach1 airframes was available, every modern fighter would have needed dive recovery flaps to prevent accidents.
True histoy show that also Typhoons, La´s, 109´s and 190´s, 262´s and P51´s crashed cause the pilot wasnt able to get out of the dive.
Originally posted by gripen
RAE and Republic data is quite clear on this; the pilot was more or less a passenger at high mach numbers.
The P-47 was a good performer at altitude and the critical mach number difference is small if compared to German fighters (couple %). But that does not mean that there was no compressibility related problems; 8th AF certainly had a reason to sent a P-47 to the RAE for the tests.
The dive acceleration is not the same thing as the critical mach number and other compressibility related issues.
[/B]
This clearly show that you still dont understand that i dont argue against the RAE results, but against the "its useless statement"!!
The P47 got into compression like most modern fighters and it got send to the RAE cause this was rather new. As i wrote before, the problem wasnt a to low critical mach, the problem was the autstanding diveacceleration, which brought the P47, same like the P38, very fast into this critical mach. Of course it would have been nice, if the critical mach would have been Mach 0,9, but as the problems with the 262 and 163 show(both had a rather high critical mach), its not the value, its how fast the plane reach this speed. The P47, same like the P38, 163 and 262 had a outstanding thrust(weight + power)/drag relation, specialy in high alt, where the the normal drag dont count that much, this result into a extreme dive acceleration, which brought this planes suprising fast into their critical mach. And its this suprising factor which need a experienced pilot and made the diveflaps to a welcome addition.
For sure the P51 did a better job regarding this, but to call the P47 "useless in high alt" is a "bit" overdone.
Originally posted by gripen
BTW there is no reason to shout all the time. [/B]
I ALWAYS THOUGH THIS IS SHOUTING. Otherwise i dont know what you want.
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Originally posted by Knegel
You clearly dont! Cause like so often you take smal things out of the whole contex!
...
The datas in combination with Browns statement, who was a member of the RAE, simply came around like its the RAE conclusion. But as i wrote, its not important here, important is that its wrong.
Well, you take a second hand quote of a person and claim it as a conclusion of the organisation. Perhaps you should actually read the reports instead rely on second hand quotes.
Originally posted by Knegel
I didnt bash the RAE, i only wrote they was wrong before, with their conclusions. Conclusions out of datas, to be used in future often are wrong, i did offer the Hurri/109 example to show this, not to bash the RAE in general.
I can't follow your logic here, basicly you make statements about the RAE conclusions without actually reading the reports. If you actually read the RAE report on the Bf 109E, you will find out that they claim Hurricane superior only in the high speed handling and the turning circles, in practically all other performance areas the Bf 109 is claimed to be better (speed, climb, dive acceleration etc.). They just over rated close range dog fighting that time.
There is nearly allways some error in the measurements and the conclusions. However, I don't see any reason to nitpick them. And in this case it's obivious that you have not even read the reports.
Originally posted by Knegel
What have this to do with the statement "the P47 was useless as high alt fighter"??
That quote is not coming from the RAE, but a second hand opinion from a person. I have no problem to live with such opinions but apparently you have.
And the connection with the RAE tests (and Republic tests as well) is that with the dive recovery flaps the pilot could regain the control and recover from the dive.
Originally posted by Knegel
This clearly show that you still dont understand that i dont argue against the RAE results, but against the "its useless statement"!!
Perhaps you (and Viking) should leave the RAE (and actually Brown too) out of discussion then.
Besides, I don't see any reason to argue about the opinion of a person. Brown is one of the great aviators of our time and IMHO deserves some respect despite what ever you think about his opinions.
Originally posted by Knegel
I ALWAYS THOUGH THIS IS SHOUTING. Otherwise i dont know what you want.
Well, you can shout with "!" as well and if you want to be loud, then "!!" as you do.
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Originally posted by gripen
Well, you take a second hand quote of a person and claim it as a conclusion of the organisation. Perhaps you should actually read the reports instead rely on second hand quotes.
Maybe you should argue with Viking, i didnt took anything than what he posted here and due to the way he posted it, i simply got the impression that was the RAE conclusion, if the RAE dont had this conclusion its even better for my argumentation. Actually i dont need to read anything than the combat reports and countless statements regarding the P47 high alt performence to disagree to the "its worthless" statement.
Originally posted by gripen
I can't follow your logic here, basicly you make statements about the RAE conclusions without actually reading the reports. If you actually read the RAE report on the Bf 109E, you will find out that they claim Hurricane superior only in the high speed handling and the turning circles, in practically all other performance areas the Bf 109 is claimed to be better (speed, climb, dive acceleration etc.). They just over rated close range dog fighting that time.
Yes, logic isnt your stron point. Basically i disagree with the "its useless statement" and similar conclusions regarding the P47´s high alt performence. And again you mix up tested datas with conclusions.
This is a RAE statement: "The Me 109 is inferior as a fighter to the Hurricane or Spitfire."
Maybe you should read more?
Originally posted by gripen
There is nearly allways some error in the measurements and the conclusions. However, I don't see any reason to nitpick them. And in this case it's obivious that you have not even read the reports.
It seems to me you realy dont get that i dont say anthing about the tested datas and the quote above show that you didnt read it.
Originally posted by gripen
That quote is not coming from the RAE, but a second hand opinion from a person. I have no problem to live with such opinions but apparently you have.
I have a problem, if such opinions get offered in a way that make belive they are RAE statements and a fact in general.
Originally posted by gripen
And the connection with the RAE tests (and Republic tests as well) is that with the dive recovery flaps the pilot could regain the control and recover from the dive.
Oh great, applaus, thats realy something new. lol
Originally posted by gripen
Perhaps you (and Viking) should leave the RAE (and actually Brown too) out of discussion then.
Besides, I don't see any reason to argue about the opinion of a person. Brown is one of the great aviators of our time and IMHO deserves some respect despite what ever you think about his opinions.
Of course Brown need respect, but if he made such a statement, it must be allowed to disagree. No??
Originally posted by gripen
Well, you can shout with "!" as well and if you want to be loud, then "!!" as you do.
Actually a "!" is made to show the reader that this sentence is more important, in his(writer) opinion. What you do is what i call nitpicking! Its realy new to me that people feel offended cause someone use a "!". :noid
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Originally posted by Knegel
Maybe you should argue with Viking...
I don't see any reason or sense to argue about an opinion of a person here.
There is errors in Viking's postings but the others have pointed them out allready.
However, you present this subjective opinion as a conclusion of the RAE, which is not true.
Originally posted by Knegel
This is a RAE statement: "The Me 109 is inferior as a fighter to the Hurricane or Spitfire."
Maybe you should read more?
Well, I have read the entire report and you should too before you make claims. That statement entirely based on turning circles and high speed handling, practically in all other performance areas the Bf 109 is claimed to be better. They just overestimated value of the close range dog fighting that time. Same way the the Zero can be claimed to be superior to the American fighters if compared only in slow speed close range dogfighting. In both cases the statement is correct in that particular context (in the case Hurricane also the high speed handling statement is correct).
Originally posted by Knegel
It seems to me you realy dont get that i dont say anthing about the tested datas and the quote above show that you didnt read it.
Well, you have continously claimed an opinion of a person as conclusion of the RAE.
Originally posted by Knegel
I have a problem, if such opinions get offered in a way that make belive they are RAE statements and a fact in general.
...
Of course Brown need respect, but if he made such a statement, it must be allowed to disagree. No??
I think that you should write to Mr. Brown and tell your opinion to him instead.
If you want argue about the RAE data, please dug up the reports first and read what actually is written there before you make claims.
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This thread has turned into a garbage bin.
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Originally posted by gripen
I don't see any reason or sense to argue about an opinion of a person here.
There is errors in Viking's postings but the others have pointed them out allready.
However, you present this subjective opinion as a conclusion of the RAE, which is not true.
I already wrote that i had the impression its a RAE statement, not only Browns opinion, i got this impression cause it was offered by Viking in one contex with the RAE testresults. I so sorry that i got this impression, realy iam so sorry.
Originally posted by gripen
Well, I have read the entire report and you should too before you make claims. That statement entirely based on turning circles and high speed handling, practically in all other performance areas the Bf 109 is claimed to be better. They just overestimated value of the close range dog fighting that time. Same way the the Zero can be claimed to be superior to the American fighters if compared only in slow speed close range dogfighting. In both cases the statement is correct in that particular context (in the case Hurricane also the high speed handling statement is correct).
I would say you be wrong!! The statement dont base only on turning circles. Its was their conclusions regarding the potential of the 109 vs Spit/Hurri as fighter. They made more strange statement in this conclusion. For example they blame the 109´s roll ratio at 400mph, while the Spitfires rollratio was same bad.
You still dont seems to understand the different between tested datas and a conclusion.
Originally posted by gripen
Well, you have continously claimed an opinion of a person as conclusion of the RAE.
Only until i got informned that my impression that Browns statement was also the RAE conclusion is wrong, but again this wasnt important for this discussion.
Originally posted by gripen
I think that you should write to Mr. Brown and tell your opinion to him instead.
The RAE should do this, cause he is/was their man, if they dont, they shouldnt wonder that people mix up opinions of their boys with official opinions.
Originally posted by gripen
If you want argue about the RAE data, please dug up the reports first and read what actually is written there before you make claims.
How often i need to tell you that i didnt argued the RAE datas of the P47 test. You even dont seems to see that its not important for this discussion who made this statement, neighter you seems to undertsnd that i already did understand that the RAE dont made such a statement and why i got the impression the RAE had this conclusion.
Anyway, the P47 discussion found an end, no good arguments against its high alt performence got offered(i was interested if there are more), so i dont will reply here anymore.
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Originally posted by Knegel
I would say you be wrong!! The statement dont base only on turning circles. Its was their conclusions regarding the potential of the 109 vs Spit/Hurri as fighter.
Let's quote the whole sentence, only the high speed handling and turning circles are mentioned in that case (some details after that):
"The Me. 109 is inferior as a fighter to the Hurricane and Spitfire. Its manouverability at high airspeeds is seriously curtailed by the heaviness of the controls, while it's high wing loading causes it to stall readily under high normal accelerations and results in a poor turning circle"
Originally posted by Knegel
They made more strange statement in this conclusion. For example they blame the 109´s roll ratio at 400mph, while the Spitfires rollratio was same bad.
I don't see anything strange there; both planes were about equally bad laterally at high speed and that was confirmed by the measurements.
Originally posted by Knegel
The RAE should do this, cause he is/was their man, if they dont, they shouldnt wonder that people mix up opinions of their boys with official opinions.
Hm... have you ever consider such remote possibility that the problem here is your (and some others) unability to tolerate different opinions.
After all Mr. Brown is one most experienced aviators around and I think that it's truly great that he still writes and travels around doing lectures etc.
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The problem is that pilots with far more experience with the P-47 than Brown disagreed with him about the dive. Brown's no idiot, but then neither was he a P-47 ace or a Republic test pilot.
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"Hm... have you ever consider such remote possibility that the problem here is your (and some others) unability to tolerate different opinions."
:D
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Well, Brown writes in the "Testing for Combat" that he did not fly much with the P-47:
"My own experience of the Thunderbolt was too short to make a thorough assessment of it, but I certainly remember it as one of the aircraft that made my adrenalin flow faster than usual."
Regarding the altitude performance Brown writes following:
"I did some general handling at 5,000 and 20,000 ft before going on up to 30,000 ft for a level speed run. It was obvious that this aeroplane was not at it's best at low level,but came into its own at high altitude. With combat emergency power I computed that after a 3 min run the true airspeed was 425 mph."
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Hmm, that definitely sounds "useless" at high altitude. I think I'm going to let you guys think what you want to think. Krusty, I thank you for your objectivity and your support of this fine fighter. By the way, I'd like to point out that no U.S.A.A.F. fighter had a better kill ratio than the Thunderbolt.
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I think you mean somebody else? :D
EDIT: Don't sweat it, I been thinking 1 name and typing another quite often, as of late.
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Originally posted by Knegel
I already wrote that i had the impression its a RAE statement, not only Browns opinion, i got this impression cause it was offered by Viking in one contex with the RAE testresults. I so sorry that i got this impression, realy iam so sorry.
You seem to have a problem understanding my posts or you simply remember wrong and don’t take the time to re-read my post before referring to them.
Here are my posts pertaining to Brown or RAE from page one:
Originally posted by Viking
Interestingly the Fw 190 has a higher critical Mach number than the P-47, so if both aircraft dived steeply enough to reach such speed the Fw 190 would pull away from the P-47. I don’t know what angle the dive would be however.
Originally posted by Viking
According to Eric Brown they actually did. See the videos I posted.
Originally posted by Viking
He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.
Nowhere do I mention RAE reports or findings except what Brown told me at the lecture.
Originally posted by gripen
Perhaps you should stop shouting and instead actually read the RAE reports and also the article on the Republic tests. The phenomena is described exactly same in the both cases; heavy and uneffective elevaror control, uneffective trim, buffeting etc. The only (minor) difference between the results is about 0,03-0,05 unit difference in the measured Mach numbers which is probably caused by measurement errors. The RAE results are probably more accurate because they were doing quite a lot high speed research that time.
Originally posted by gripen
I don't think that there is somekind of accurate/exact/final truth on this kind of issue. It can be said that at least in the tested configuration (both tests, RAE and Republic) the P-47 had some undesirable characters at high mach numbers. Anyway, they certainly had a good reason to add the dive recovery flaps.
A voice of reason, how refreshing. Of all the fighters of WWII to my knowledge only two had to have dive flaps mounted to alleviate dangerous dive characteristics: P-38 and P-47.
As always people will have to draw their own conclusion, but I think this thread is done.
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Gripen,
I think your Brown quotes don't deal with diving tests, right?
The same man writes in his book 'Wings On My Sleeve' (pp.70-72): "The big job in Aerodynamics Department when I arrived was the exploration of high-speed flight problems. It was te first full-scale research in the country on the compressibility of airflow causing loss of control at transonic speeds - the first probing of the sound barrier. Chasing higher and higher Mach number decimals we dived our machines from high altitude until they began to go out of control.
This transonic flight testing took a new emphasis after a visit to RAE early in 1944 by Lt.Gen. Jimmy Doolittle, who had just taken over command of the 8th USAAF. This American air force had started worrying fighter losses when the fighters on high cover over Flying Fortresses dived down to intercept German fighters attacking the bombers and lost contreol before they could engage the enemy in combat.
Americans needed urgent help, and RAE was the world leader in transonic flight testing. There was no time to set up normal instrumented research programme, but what was wanted was a hands-on series of tests on three USAAF escort fighters - the P-38H Lightning, P-47C Thunderbolt and P-51B Mustang. The requirement was for detailed description of the handling behaviour of these aircraft at high speeds up to their tactical (manoeuvring) and critical (loss of control) Mach number, so that the operational pilots could recognize they were near these limits without reference to instruments in the cockpit."
"We knew from tests at RAE on captured German fighters that the Me109 and Fw190 both had tactical Mach number of 0.75, so that figure was the name of combat game at 30,000 feet. The tests we conducted on the American fighters revealed that the Lightning and Thunderbolt fell well short of that figure, with tactical Mach numbers of 0.68 and 0.71 respectively. However, the Mustang with its laminar-flow wing achieved 0.78 tactically, and soon after receiving these results Doolittle asked that his Force be supplied with only P-51Bs."
I suppose this might not have been the only reason for requesting Mustangs, but Brown does not discuss any other reasons (e.g. range) in this text. I think he might be jumping into a conclusion or at least making a pretty big shortcut.
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Here is the diving part from the "Testing for Combat" (p.145-146):
"Before next flight a Machmeter was fitted to the aircraft, and as intructed I climbed to 35,000 ft, carried out a 2 min level run at full power and trimmed the aircraft before pushing over into a 30 degree dive. At Mach=0.72 the aircraft began to buffet slightly and pitch nose down, requiring a strong pull force to maintain the dive angle. At Mach=0.73 the buffeting increased severely and the nose-down pitch was so strong that I needed a full-blooded two-handed pull to keep the dive angle constant. I had to hang on grimly in this situation, unable to throttle back until Mach number decreased as altitude was lost. The pull-out was not effected until 8,000 ft. Analysis showed that a dive to M=0.74 would almost certainly be a 'graveyard dive'.
I have only subsequently experienced such severe compressibility nose-down pitch effects in two other aircraft, the Messerschmitt 163B and the Grumman F8F Bearcat. Anyway, the RAE recommendation was to fit a dive recovery flap on the underside of the wing which when activated would give a nose-up pitch to counter the compressibility nose-down pitch. This was eventually fitted to all Thuderbolt models."
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Hi Viking,
this made me believe it was also a RAE conclusion:
Originally posted by Viking
He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.
As i wrote before, i got this impression and obvious it was a mistake, but it have nothing to do with the fakt that history did proof the P47 to be a very good high alt fighter also without the flaps.
And it looks like even Brown wasnt the opinion the P47 was useless as high alt fighter, therefor it dont matter even more who made this statement.
The low critical mach was a disadvantage, nothing to argue, but the P47 had otherwise huge advantages in 30k alt. And actually the critical mach problems in 30k isnt that a problem for the headline question of this theatre anyway.
In a dive from 25k downward, we get a absolut different picture.
Greetings,
Knegel