P-39 Turbo - Here We Go Again

[MIflyer]

Just got an e-mail from Flight Journal that provided a nice picture and repeated this hoary old claim:

"Although the Bell P-39 Airacobra was designed as a front-line fighter, one loaded with a lethal combination of both cannon and machine guns, its high-altitude dueling attributes were nonexistent. The original design called for a turbo-supercharger that would have taken the P-39 to new heights, but to save weight, Bell decided to take it out."

Uh, no. The turbo actually gave LOWER performance than the V-1710 without one. You could not fit one in an aircraft as small as a P-39. It caused more drag than it was worth. Note that what would have been the pilot's position in a P-38 boom was taken up by the turbo. And on the XP-37 the cockpit had to be put absurdly far in the back, like a Gee Bee.

 

[wuzak]

The XP-37/YP-37 had to have the cockpit so far back because the coolers (radiator and intercooler) were placed behind the engine.

The turbo was placed, like the XP-39, beneath the engine.

 

[special ed]

Is P-39 Expert writing for Flight Journal now?

 

[Shortround6]

Although the Bell P-39 Airacobra was designed as a front-line fighter, one loaded with a lethal combination of both cannon and machine guns, its high-altitude dueling attributes were nonexistent. The original design called for a turbo-supercharger that would have taken the P-39 to new heights, but to save weight, Bell decided to take it out

Wait!!!
I thought it was the guys at NACA/Wright field that recommended the turbo be taken out?
At the behind the scenes request of the whisper "bomber mafia" ?

All over the objections of the Bell guys.

Story fails to take into account that the existing XP-39 would not have gotten a production contract due to low performance at any altitude but conspiracy sells better.

 

[MIflyer]

Story fails to take into account that the existing XP-39 would not have gotten a production contract due to low performance at any altitude but conspiracy sells better.

Yes, the single stage V-1710 was faster than the tubocharged version. Oddly enough Flight Journal had an article that said all that several years back.

I have a copy of a P-39 article from a model magazine with very nice artwork that says "An airplane designed for tank busting on the steppes of Russia did not do well in the South Pacific." Oh, puuuuhleeeease....

 

[PStickney]

Just got an e-mail from Flight Journal that provided a nice picture and repeated this hoary old claim:

"Although the Bell P-39 Airacobra was designed as a front-line fighter, one loaded with a lethal combination of both cannon and machine guns, its high-altitude dueling attributes were nonexistent. The original design called for a turbo-supercharger that would have taken the P-39 to new heights, but to save weight, Bell decided to take it out."

Uh, no. The turbo actually gave LOWER performance than the V-1710 without one. You could not fit one in an aircraft as small as a P-39. It caused more drag than it was worth. Note that what would have been the pilot's position in a P-38 boom was taken up by the turbo. And on the XP-37 the cockpit had to be put absurdly far in the back, like a Gee Bee.

View attachment 771565

Here are the numbers - the XP-39 is Aircraft 9 in the report

Search - NASA Technical Reports Server (NTRS)

ntrs.nasa.gov

NACA-WR-L-489

 

[GregP]

I'm sort of tired of hearing about the XP-39.

In reality, it didn't perform badly and climbed VERY well, mainly as a result of being quite light. When I look up it's performance, I see it climbed from 0 - 20,000 feet in 5 minutes. Not bad. It came in at 3,995 lbs empty and 5,500 lbs loaded. After NACA-recommended changes, it came in at 4,530 lbs empty and 5,834 lbs loaded. If it got heavier later, and it DID, then it was in good company as ALL WWII US fighters got heavier as they were "successively improved." The P-39Q had a maximum takeoff weight of 8,400 pounds, so I'm guessing that a weight of 6,100 lbs would have been very nice indeed for performance later.

I'm also a bit uncaring about the turbo drama. It doesn't matter WHO caused the removal of the turbocharger. The only important fact is that the XP-39 was the only turbocharged P-39 ever built, and it never went to war, so it didn't affect the outcome of even one battle, much less the war. I believe they COULD have turbocharged the airframe, but not in the original size. It would have needed another 1 to 2 feet of length. When the NACA finished with their wind tunnel recommendations, the new length was to have been 29 feet 9 inches instead of the original 38 feet 8 inches. What effect would another foot make? Not much.

Here's the real kicker though ... they didn't do it. I hope we can agree on at least that. So, talking about what might have been if a turbo was fitted is a bit pointless as it never happened. What they actually GOT was the Airacobra we all know and love to hate. They ALSO got a plane that was never tested with empty ammunition bays, thus hiding a serious design flaw when the CG migrated aft as ammo was used up in combat. Taken together, the series of mistakes and misguided decisions resulted in a reasonably horrible airplane that nevertheless flew decently if not for long distances, unless pushed into fighter-like corners of the flight envelope. Since it was supposed to BE a fighter, that didn't work out very well for the U.S.A. or the UK.

But, somehow, the Soviet Union found in the Airacobra a very GOOD fighter and attack aircraft that was well-liked by the Soviet pilots and crews. The P-39 had a Soviet experience similar to what the Finns had with the otherwise unliked F2A Buffalo. What we can really say is it was there in the war. Some people liked it ... mostly Soviet. Others, generally in U.S. or British service, didn't.

I have had the good fortune lately to be working on a static restoration of a P-39, among other projects (B-17 display cockpit, B-17 aircraft, and C-47 Service Bulletins). When the P-39 gets done, I'll post some pics. The main guys on it have been doing a good job, especially considering the shape it was in when the project kicked off. My restoration partner and I did some lower rear fuselage sheet metal work to help, but that was just a drop in the bucket on the overall P-39 job. This thing was in rough shape to start with!

 

[Peter Gunn]

I agree with GregP a bit tired of hearing about it but on the flip side, man what a looker. It still makes my top 3 best looking fighters of WWII, YMMV of course.

 

[special ed]

I agree with GregP a bit tired of hearing about it but on the flip side, man what a looker. It still makes my top 3 best looking fighters of WWII, YMMV of course.

Like a lot of women. Look really good, but not in the long run.

 

[Shortround6]

XP-39 was using a lot of Spanx, make-up, wig and higher than normal heels.
And a fictitious bank account.

 

[SaparotRob]

XP-39 was using a lot of Spanx, make-up, wig and higher than normal heels.
And a fictitious bank account.

Sounds like the woman who introduced me to my ex-wife.

 

[GregP]

Like a lot of women. Look really good, but not in the long run.

Sort of like a great-looking bimbo ... not much upstairs but, man, what a staircase!

 

[Peter Gunn]

I'm Peter Gunn, and I approve of the four posts above this one.

 

[GregP]

Obviously a bit overboard ... so ...