XP-39 and the Claims

You too. Cheers.

Thanks, Shortround. You summed it up nicely. The claim is that the Bell XP-39 hit 390 mph at 20,000 feet in 1939 in the original test configuration.

We can't prove it happened and we can't prove it didn't happen at this time. It seems unlikely to me that it did, but neither you nor I can say for sure as you say plainly above. There ARE reports it did exactly that originate from what I would say are widely-accepted sources for other data as well as suppositions that it didn't from other widely-accepted sources.

In summary, as stated many times before: It can't be proven either way at this point, but the preponderance of evidence points in the direction of about 375 mph at best and perhaps 357 mph at worst at 20,000 feet in the configuration in which it was supposedly flown in 1939, before it went to the NACA wind tunnel.

That's about as certain as I can say it, and it seems like a reasonable summary to me. Perhaps you think you know better with some certainty? That would require evidence (proof) of same which I have been unable to locate. If you have it, for heaven's sake present it. I'd love to see it. If you don't then, as much as it seems unlikely, we basically agree that it LIKELY didn't go that fast.

If there WAS a test flight (seems like there was to me), there IS a report somewhere on it, assuming it survives in some form. So, it still may surface at some point, maybe not because it is lost. If not, then nobody knows what it says other than speculation.

And it only took 10+ years to come to that. I'd have thought we'd agree on that much in our first exchange on the subject, but it seems like we don't agree on much very often ... or maybe we actually do, and just disagree on the things we go back and forth about, which seems more likely.

Hey admiral Beez,

The original claim I saw came from "American Combat Planes by Ray Wagner. My original copy was dated 1960, but I lost that in a Tornado in Indiana when I was Purdue University in the late 1960's / early 1970's. My current copy is dated 1982 and the list of sources is not all THAT long; some 3 1/2 pages in something like 12-point font.

Since you asked, I looked at Ray Wagner's sources. Among them is "U.S. Army Aircraft (Heavier Than Air) 1908 - 1946 by James C. Fahey, copyright 1946, published by Ships and AIrcraft, P.O. Box 48, Falls Church, Virginia." Library of Congress card number 46-7791.

As luck would have it, I have a pristine copy that I have not looked at for more than 20 years, but I took it out to check on this. On page 33, it lists the Bell XP-39 at 390 mph, aircraft ordered in FY 38, delivered in FY39. It lists the gross weight at 6,204 lbs. and says the Allison was a V-1710-17 of 1,150 HP. It doesn't state an altitude or rpm. Among Mr. Fahey's sources are many U.S. Government agencies including Officers and Personnel of the Technical Data, Still Photo, and other sections of the "The Air Technical Service Command, Wright Field." No single source is mentioned for the XP-39 or any other data. He seems to have about 20 U.S. Government sources and only a few civilian ones.

Perhaps Mr. Fahey started this can of worms based on Wright Field information, I can't say for sure.

GregP said:

In summary, as stated many times before: It can't be proven either way at this point, but the preponderance of evidence points in the direction of about 375 mph at best and perhaps 357 mph at worst at 20,000 feet in the configuration in which it was supposedly flown in 1939, before it went to the NACA wind tunnel.

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It does?

What evidence is that?

wuzak said:

It does?

What evidence is that?

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NACA estimated the XP-39 would have a top speed of 340mph @ 20,000ft in its original configuration. Which strongly suggests that the top speed achieved before it went to NACA was less than 340mph.

NACA also estimated that a cleaned up turbocharged XP-39 would have a top speed of 392mph @ 20,000ft. Could this be the source of the XP-39 managing 390mph?

See XP-39 and the Claims

Enough trolling, Wayne. Read the thread.

It isn't fun anymore.

Here Wagner writes 365 mph at 20,000 ft ?!

P-39 by Ray Wagner - Page 1

P-39 Expert said:

And I still don't consider escort missions to Holland, Belgium and a sliver of France to be meaningful. Not when your main target is Berlin.

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Thank heaven you weren't planning air raids during the war, then. Your tenure as strategic planner would be very short indeed.

Reluctant Poster said:

Which in turn reminds me of Monty Pythons philosophers soccer match

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Where would the world be without Monty Python to put it all into context?

pbehn said:

Well yes, but you do what you can with what you've got, the Spitfire Mk IX was only castigated because of its range when aircraft with similar performance and longer range were available, up to that point it was used to B-17s on raids. If you take airforces out of it, there was a learning process by all involved, improving bombers and fighters, range and load and defence and function. Even if you just want to bomb Germany you have to drive air defence out of North France Belgium and Netherlands to maximise the number of routes into Germany, but as per my previous post the Ruhr area was a centre of German heavy industry and actually has more people than Berlin.

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Actually the 8th Airforce thought just the opposite. The theory was that the since the defenses were supposedly concentrated near the coast, once they broke through the strong defense the opposition would be much weaker in the interior. This would allow the unescorted bombers to reach the target without prohibitive losses. This theory was tried in the August 1943 with the first Schweinfurt raid. At that point the theory must have seem a bit suspect, but it took a few more catastrophic raids to finally put an end to the unescorted bomber theory.

This is an excerpt from the attached paper

It's my experience that if you read long enough you can find somebody who made some statement sometime ago that agrees with your position. And some that don't.

And a whole lot of it is hearsay passed down from some sage from way back who isn't around anymore. After a while these hearsay arguments are taken as fact. And a lot of them contradict each other.

Then wwiiaircraftperformance.org somehow materializes in 2006 and now we have the actual govt/military performance tests. Updated through 2015 these are actual test documents from the US, GB, Germany and Japan (no Soviet section?). Now all is revealed. As fact, not some opinion from '42 that may be grounded in fact but then again may not, made by someone who may have an ax to grind, or not. How the hell can we know? No matter, now we have the actual facts from the original tests.

Back to wwiiaircraftperformance.org. I understand the owner/founder is a gentleman named Mike Williams who is a member of this chat board. I have seen his name periodically at the bottom of the page under "Users who are viewing this thread". Now I don't know Mr. Williams personally as apparently some on here do. I had in the past emailed him asking about information on (you guessed it) the P-39 among others. I never got an answer to my emails (no problem, I'm sure Mr. Williams is plenty busy with other duties) but then shortly after the P-39 information began to appear. Thanks so much Mr. Williams. Just a few questions below?

1. The latest additions to your excellent site are from 2015. Will there be more posts? Is there more information waiting to be put on the site?
2. Regarding specifically the P-39N, your performance tests offer information that I as a voracious reader for the last 65 years had not seen before. Previously all I ever saw regarding the N was "Top speed 399mph. Service ceiling 38500ft". Just asking, but are you the only person with this information? Do you have the only copy of those specific tests? Only reason I am asking is your site is the only place I have ever seen that information. And, yes, do you have any more information on the P-39?

Mr. Williams, thanks for you site and all the valuable (and until now somewhat secret) information it provides. Hope I am not invading your privacy with these questions.

Thanks again.

I have to say you hit the nail on the head, P-39 Expert.

Thank you Mike Williams for coming up with such a great website.

Reluctant Poster said:

Actually the 8th Airforce thought just the opposite. The theory was that the since the defenses were supposedly concentrated near the coast, once they broke through the strong defense the opposition would be much weaker in the interior. This would allow the unescorted bombers to reach the target without prohibitive losses. This theory was tried in the August 1943 with the first Schweinfurt raid. At that point the theory must have seem a bit suspect, but it took a few more catastrophic raids to finally put an end to the unescorted bomber theory.View attachment 579310

This is an excerpt from the attached paper

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There were many theories. The bomber will always get through. The bomber box can defend itself. Long range escort was impossible. Long range escort was vital. Bombing can win the war alone. Bombing Germanys ball bearing plants can end the war early. As far as I can see the theory of a "fighter belt" was put forward by someone whose fighters can only reach that fighter belt. Any discussion with RAF recon pilots, with RAF bomber command and look at the Battle of Britain would show it is a convenient fantasy. Any Me110 is an effective fighter against unescorted bombers and Germany obviously had them as night fighters. RAF recon could tell them there were fighters behind any "fighter belt". In Jan 1943 in the famous raid on Goerings radio transmission one Mosquito was shot down south of Berlin. Dowding and Park didnt have a "fighter screen" so why would anyone suppose the Germans had, and why would anyone suppose it wouldnt be moved back out of range of enemy fighters. If you amble into central Germany at 180mph the fighters who met you on the way there have time to land re fuel and re arm and meet you on the way back and fighters from well off the line of the mission can be called into the battle.

pbehn said:

There were many theories. The bomber will always get through. The bomber box can defend itself. Long range escort was impossible. Long range escort was vital. Bombing can win the war alone. Bombing Germanys ball bearing plants can end the war early. As far as I can see the theory of a "fighter belt" was put forward by someone whose fighters can only reach that fighter belt. Any discussion with RAF recon pilots, with RAF bomber command and look at the Battle of Britain would show it is a convenient fantasy. Any Me110 is an effective fighter against unescorted bombers and Germany obviously had them as night fighters. RAF recon could tell them there were fighters behind any "fighter belt". In Jan 1943 in the famous raid on Goerings radio transmission one Mosquito was shot down south of Berlin. Dowding and Park didnt have a "fighter screen" so why would anyone suppose the Germans had, and why would anyone suppose it wouldnt be moved back out of range of enemy fighters. If you amble into central Germany at 180mph the fighters who met you on the way there have time to land re fuel and re arm and meet you on the way back and fighters from well off the line of the mission can be called into the battle.

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I would put your original post in the same category.

Reluctant Poster said:

I would put your original post in the same category.

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In what way.

I've skipped around this thread while eating popcorn. Has anyone brought up Mike Williams page on the P-39?

P-39 Performance Tests

It has been alluded to but the production P-39s, as you know, are not representative of the XP-39 in either of its forms.

Thanks for the link above, it always takes me awhile to find the aircraft I want to look up, but it's also well worth the time. Mike surely has a great website.

GregP said:

It has been alluded to but the production P-39s, as you know, are not representative of the XP-39 in either of its forms.

Thanks for the link above, it always takes me awhile to find the aircraft I want to look up, but it's also well worth the time. Mike surely has a great website.

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There's info on the XP-39B but it's shown that it has put on some weight since April 6, 1939.

FLYBOYJ said:

There's info on the XP-39B but it's shown that it has put on some weight since April 6, 1939.

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So, we're twelve pages into this topic, talking about the XP-39s top speed, the P-39's external tank capacity and range and the P-39N's performance to a point where minutia has been exhausted. After all that, so what? The P-39 had a dismal record in air combat in AMERICAN service. Woulda coulda shoulda aside, the P-39 was deemed unsuitable for AMERICAN use, which is why it was purchased by the AAF. It wasn't designed as an export fighter for the Russians.