Help with P-40 ID

[GregP]

Yes it did.

[Elwyn]

The P-63's had 4 blade props also.

[k5083]

So did some P-39 racers, and P-51A 43-6006 "Polar Bear" sometimes wears one.

August

[Dan K]

So did some P-39 racers...

And not just P-39 racers. Over 800 P-39Q-21 and P-39Q-25 exited the production line with four-bladed props.


P-39Q-21: 109 P-39Q-20 fitted with a four-bladed Aeroproducts propeller.

P-39Q-25: Production variant similar to the P-39Q-21 but with a reinforced aft-fuselage and horizontal stabilizer structure; 700 built.


Example in VVS markings:

http://i252.photobucket.com/albums/hh2/ ... /P-39Q.jpg


Some vintage footage of Russian four-bladed P-39Q's (starts about 2:40):

https://www.youtube.com/watch?v=NRC6yUFcoPY

[ArtATP]

Interesting YouTube on the P39, why was it that it was disliked by the US Army, but seemed to be loved so much by the Soviets? Was it related to the geography of their battle zone??

What was the apparatus seen on the tails of the P39 for what looks like test flight/spin tests? A drogue chute??

Art

[Dan K]

Interesting YouTube on the P39, why was it that it was disliked by the US Army, but seemed to be loved so much by the Soviets? Was it related to the geography of their battle zone??

What was the apparatus seen on the tails of the P39 for what looks like test flight/spin tests? A drogue chute??

Art

No time to answer presently, but here's a good spot to start:

http://lend-lease.airforce.ru/english/a ... /index.htm

http://lend-lease.airforce.ru/english/a ... /part2.htm

[GregP]

There are several reasons why we didn't like it and the Soviets did.

1) The air war in the Soviet Union was a low-altitude war as Joseph Stalin viewed aircraft as support for the ground troops. The Germans initially tried to get the Soviets to come up to altitude and fight, but the Soviet units ignored the german high altitude fighters and went in down low and killed the German troops, forcing the Germans to come down and fight where the Soviet aircraft were operating. Down low, the P-39 was a pretty good airplane.

2) The Soviets liked the cannon armament and some P-39's and P-63's were retrotitted with superior Soviet cannons rather than the jam-prone American Oldsmoblie cannons.

3) Deleting the turbocharger from the P-39 turned it from a high-altitude aircraft into a low-to-medium altitude aircraft. That made it less than wonderful for the ETO, which was a high-altitude war for most of the war. It wasn't so bad in the MTO and PTO because these were lower-than-ETO-altitude theaters.
Larry Bell originally proposed deleting the turbo because he was desperate for business, the P-39 turbo installation was having issues, and his chief designer was away on a European trip at the time. Once it was deleted, they could never get the turbo reinstated, despite trying at least three times.

4) The P-39 had a balance problem when the ammunition was depleted. If you shot up all your ammo, then you were at or slightly behind the aft CG limit and bad things could happen around stall. They did a study of the P-39 during the war and could NOT make the P-39 tumble or misbehave, but all the flights were with full ammunition. Some years after the war they reran that study with no ammunition and the aircraft tumbled at stall. It was an eye-opener for the USAAF.

6) For some reason we also didn't like the P-63. It probably had something to do with the fact that it LOOKED like a P-39. But the P-63 was an altogether different anmial and could give a P-51 all it could handle and had good altitue performance where it was some 12 - 15 mph slower than a P-51 but otherwise outperformed the Mustang in large part. It rolled better, climbed better, and hit harder. I think we also didn't buy it because anyone could see the war was being won with the aircraft on hand. So why introduce another one that would be as good as the one you have? That adds another supply-line chain and means retraining fior units that transistion to the new type.

I would think that adding a 4-blade prop to a P-39 would be VERYdestabilizing without tail area adjustments. Mike Carrol's fatal crash was almost certainly due to adding a 4-bladed prop without increasing the fin area, combined with shorter wings and low experience in high-powered aircraft. I know some WERE delievered that way, but wind tunnel tests showed it probably could not handle the extra side area forward without an increase in fin area to compensate. I have never seen one of the 4-bladed P-39s in person, but would love to so I could look careully at the fin and dorsal spine areas.

There is a lot of detail left out here, but the basics are correct.

One last observation ... there are a lot of pilots who aren't comfortable with a drivehaft spinning between their legs only a couple of inches from delicate parts.

[ArtATP]

Dan K, thank you for that most informative report on their importation and use of the P39's.

Interesting comment at the end:

On 5 November 1943, the notes of a conversation of the ambassador of the USA A. Harriman with ..., V. M. Molotov: "There is one type of airplane, namely the Airacobra, which is used very well by the Soviet air forces. Harriman says that the Russians use this airplane even better than the Americans. Therefore Vandenberg (General, ... of the US Army Air Force) would be wise to acquaint himself with the experience of Soviet pilots. In connection with this, Vandenberg would want to visit Soviet squadrons equipped with the Airacobra aircraft. ...

I had previously seen some reports on what they (Soviets) went through in lightening them by removing armement and some other modifications.

I wonder how much of it was just due to: "The pilots loved their Airacobras for comfort and good protection. As one P-39 pilot expressed it, he felt like he was "flying in a safe". Airacobra pilots did not burn because the aircraft was metal and the fuel cells were positioned far away in the wing. They were not subject to jets of steam or streams of oil because the engine was behind them. ..." Where veteran (US) pilots I met long ago definitely hated the type, seemed mostly due to their 'flat-spin' tendencies.
_______________________________________________________________________

Greg P's summary was excellent, imagine never considering a CG shift involved with having all that expendable ordnance located so far forward, wonder how that affected the P38's and Mosquito's?

Art

[Dan K]

Digressing rabidly (but as long as we're talking Allisons with four blades...)

http://aviadejavu.ru/Images6/MM/MM-92/0066-01-2-3.jpg

[Brenden S]

If you send me a high res image I could colour it in for you if you want?

[Mark Allen M]

Same airplane?


Pearl harbor c 1968

[Warbirdnerd]

Mm could be. I don't think there was more than one modified like that. Nice Tora Zero behind it. One thing is for sure, that isn't Jack Cook in front of it, his hands are not in his pockets!

[Mike]

...some P-39's and P-63's were retrotitted...

[ams007]

Here is my 1/72 model of N5672N that i have just finished. Modified with a 4 blade prop (I think off an RE8 ) and i puttied over the rear windows. All decals are hand made. The photo is a bit washed out, because the exhaust is not white.

Hopefully i have done it justice

[Lon Moer]

One more from the Registry



The canopy was lost in flight during the filming of T-T-T and then later during filming it had a landing gear incident that resulted in the 4 blade prop.
Tom Camp later acquired and restored it at Livermore CA., where John Paul was also restoring P-40's.
They were very active on the Warbird circuit here in NorCal in the late '70s.