On one of the threads in here, someone said that the USA conducted tests where they tried to intercept the B29 with the P51, P47 and I think also the P38. I remember they said that even the P47 was going into high speed stalls at altitudes above 30,000 feet while trying to make gun runs. Can someone post those tests for me? Or at least elaborate on the findings.
USAF tests: Intercepting the B29 with the P51, P47 and P38
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Jabberwocky
Staff Sergeant
I don't have the USAF tests, but here are the RAF tests of Vampires and Meteors against the B-29.
View: https://www.youtube.com/watch?v=-dMog3T3CAc
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As I recall, the person said they were high speed stalls. I assume that they were trying to maneuver sharply in the thin air at high altitude in order to dodge "return fire", but, this is why I would like to read the actual USAF tests if someone has them.
drgondog
Major
It is discussed in The Report on the Patuxent River Fighter Conference - Oct 1944. The stalls occurred when the P-51s were attempting high G pursuit curves in beam attacks on the B-29. Apparently the B-29 was flying close to 340 TAS at 30,000 and higher.
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drgondog
Major
Nope - you'll have to read the report. IIRC it is discussed around pag 171 - but I will look it up.
I think I saw a claim somewhere that testing of the stripped bombers configured to carry atomic bombs demonstrated that the P-47s had trouble keeping up due to engine overheating.
It may be that the high altitude performance of the P-47 was a little over-rated. Certainly, its engine had a much better high altitude performance than the single stage supercharged engines of its German contemporaries. However, this was somewhat offset by the low aspect ratio of the wing and the relatively high wing loading compared to most other allied fighters.
It may be that the high altitude performance of the P-47 was a little over-rated. Certainly, its engine had a much better high altitude performance than the single stage supercharged engines of its German contemporaries. However, this was somewhat offset by the low aspect ratio of the wing and the relatively high wing loading compared to most other allied fighters.
Matt308
Glock Perfection
You sometimes amaze me.
GregP
Major
You've heard of the "coffin corner?"
The early Lears, at max ceiling, were only 3-5 knots from stall on the low end and 3-5 knots from Mach tuck if they went any faster.
In the P-47, as in any normal aircraft, the stall speed goes up with decreasing air density and it is probable that if the service ceiling was 43,000 feet, then the stall margin at 30,000 feet was smaller than appreciated. He may only have had 3 g available or perhpas even less, so a mild pull on the stick at sea level could easily tunr ino a stall at high altitude. Nobody was dogfighting at 35,000 feet in WWII ... they were making gentle turns and trying to get a good sight picture.
I have read about encounters between Grumman Panthers and Soviet MiGs at high altitude and all it took to spoil the MiG's aim was a slight turn into the path of the MiG ... and there was simply not eough g-available for the MiG to get a firing solution, so he'd go around again and make another try. They played cat and mouse for several passes and the MiGs got low on fuel and departed for home base as the Panther withdrew.
The early Lears, at max ceiling, were only 3-5 knots from stall on the low end and 3-5 knots from Mach tuck if they went any faster.
In the P-47, as in any normal aircraft, the stall speed goes up with decreasing air density and it is probable that if the service ceiling was 43,000 feet, then the stall margin at 30,000 feet was smaller than appreciated. He may only have had 3 g available or perhpas even less, so a mild pull on the stick at sea level could easily tunr ino a stall at high altitude. Nobody was dogfighting at 35,000 feet in WWII ... they were making gentle turns and trying to get a good sight picture.
I have read about encounters between Grumman Panthers and Soviet MiGs at high altitude and all it took to spoil the MiG's aim was a slight turn into the path of the MiG ... and there was simply not eough g-available for the MiG to get a firing solution, so he'd go around again and make another try. They played cat and mouse for several passes and the MiGs got low on fuel and departed for home base as the Panther withdrew.
drgondog
Major
I dunno why pg 171 stuck but there it was. BTW there is as good a monologue regarding Stability and Control Issues and design approaches as I have ever seen by NACA's Mel Gough starting on page 32. For those that are curious but so much so as to dive into the math this is as good as it gets...
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