Which P-39 Model Had Longer Wings?

MIflyer

1st Sergeant
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May 30, 2011
Cape Canaveral
I have been reading a book recommended by one of the members here, "Cobra Combat" by Robert E Case. He flew P-39's in the Solomans in WWII, starting in April 1943. It is a good book, with lots of interesting although he does get some things wrong, sucha s saying the P-39 had the supercharger deleted but the P-40 did not. But one item does not seem to be a mistake.

On one mission a Japanese 12.7 MM machine gun his his wing, doing a lot of a damage to it, including splitting the spar. He made it back to base Okay but the tire was shot off the wheel on the damaged wing and it was a rather rough landing. He figured he would have a few days off while they got him another airplane, but in fact they got his fixed right up. They explained they had taken one wing off a wrecked P-39 and installed on his airplane, but it was from a different model and the wing was longer that the original one. The Bell tech rep assured them that was Okay and it had been tested at the factory. Case said that the airplane few just fine with the longer wing and even seemed to be more stable. Unlike the supercharger nonsense, which has been spread around for decades, this story is very specific and believable.

I looked at all the P-39 references I have, "Squadron P-39 In Action," William Green "Fighters Book 4," "Airacobra Advantage" and "P-39 in Detail and Scale." All of them show the wingspan of all of the production P-39's as 34 feet. Given the high wing loading I would not have been surprised if they added a bit to the wing in the later production models, but there is no indication of that. Anyone ever hear of that modification?
 

FLYBOYJ

"THE GREAT GAZOO"
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Mod
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I have been reading a book recommended by one of the members here, "Cobra Combat" by Robert E Case. He flew P-39's in the Solomans in WWII, starting in April 1943. It is a good book, with lots of interesting although he does get some things wrong, sucha s saying the P-39 had the supercharger deleted but the P-40 did not. But one item does not seem to be a mistake.

On one mission a Japanese 12.7 MM machine gun his his wing, doing a lot of a damage to it, including splitting the spar. He made it back to base Okay but the tire was shot off the wheel on the damaged wing and it was a rather rough landing. He figured he would have a few days off while they got him another airplane, but in fact they got his fixed right up. They explained they had taken one wing off a wrecked P-39 and installed on his airplane, but it was from a different model and the wing was longer that the original one. The Bell tech rep assured them that was Okay and it had been tested at the factory. Case said that the airplane few just fine with the longer wing and even seemed to be more stable. Unlike the supercharger nonsense, which has been spread around for decades, this story is very specific and believable.

I looked at all the P-39 references I have, "Squadron P-39 In Action," William Green "Fighters Book 4," "Airacobra Advantage" and "P-39 in Detail and Scale." All of them show the wingspan of all of the production P-39's as 34 feet. Given the high wing loading I would not have been surprised if they added a bit to the wing in the later production models, but there is no indication of that. Anyone ever hear of that modification?
The wings actually got shorter when compared to the prototype.

1654809601384.png
 

MIflyer

1st Sergeant
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May 30, 2011
Cape Canaveral
The wings actually got shorter when compared to the prototype.
Yes, and there was also the P-39E which had an experimental wing that was a different length, but nothing that would have showed up in the SWPA would have had anything but 34Ft.

I wondered about them splicing on a longer wing section but the gear on the shot up side was badly messed up too, so they would have to include the whole wing on that side. I am impressed they could do that so quickly on the 'Canal.

And while things were always rough on the 'Canal I guess they got better in mid-1943 because they flew over to New Guinea to the exhausted P-39 units there to let them fly some of their P-39's since they had been all but wiped out. I did not think that New Guinea was a picnic but I never knew that at any time it was worse than the 'Canal.
 

FLYBOYJ

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Yes, and there was also the P-39E which had an experimental wing that was a different length, but nothing that would have showed up in the SWPA would have had anything but 34Ft.
There were 2 "XP"-39Es built with squared off wingtips. 35 feet 10 inches. One crashed during a spin test (Imagine that!)
I wondered about them splicing on a longer wing section but the gear on the shot up side was badly messed up too, so they would have to include the whole wing on that side. I am impressed they could do that so quickly on the 'Canal.
Not likely - that would change the configuration of the aircraft and unless it was a matter of life or death (which "could have" happened on the canal) I see no maintenance officer in their right mind to allow an aircraft to fly outside of SRM specifications unless they got authorization from the factory.

I see this whole story as a myth - all production models of the P-39 maintained the same wingspan. There might have been a repair tolerance in the SRM that allowed some deviation but this would be negligible. For the time it would take to repair a wing, it would be easier to install a whole new one. The following shows a P-39 being assembled in the field. You can see how the wing is installed.

This story sounds like a "Cadinism"

 

MIflyer

1st Sergeant
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May 30, 2011
Cape Canaveral
Well, the guy who was there and who describes many of his experiences in detail said it occurred. Perhaps they just used a wing from a different model and for some reason he thought it was longer. They had both P-39D's and P-400's on the "Canal and by the middle of 1943 they could have F, J, K, and M models as well. Building airplanes out of pieces of wrecks was quite common on the 'Canal. VT-8 did it as well with TBF's.
 

FLYBOYJ

"THE GREAT GAZOO"
Staff
Mod
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Apr 9, 2005
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Well, the guy who was there and who describes many of his experiences in detail said it occurred. Perhaps they just used a wing from a different model and for some reason he thought it was longer. They had both P-39D's and P-400's on the "Canal and by the middle of 1943 they could have F, J, K, and M models as well. Building airplanes out of pieces of wrecks was quite common on the 'Canal. VT-8 did it as well with TBF's.
That is more plausible - it seems the basic P-39 airframe remained the same through out production and if you watch that video, the process for the wing installation is pretty straight forward. I doubt the basic construction of the wing between models changed much as the P-39D and P-400 were basically the same airframe.
 

MIflyer

1st Sergeant
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6,954
May 30, 2011
Cape Canaveral
By the way, there was a version of the P-39F where they installed additional armor to cover the radiator. That may be the basis of one pilot's claim that they improved the performance in the field by removing some of the belly armor.
 

ddwhitney

Airman
20
36
Apr 9, 2020
Hello All,
Sorry to disappoint, but ALL P-39s were built with the 34'-0" wing, beginning with the prototype XP-39. The only exceptions were the three XP-39E's, which were highly modified to test the new two-stage Allison V-1710-47 for the P-63. See attached. This information comes from copies of the relevant Bell Specifications and reports.
 

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  • Lengths of P-39 Wings.doc
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MiTasol

Chief Master Sergeant
3,987
4,924
Sep 19, 2012
Perhaps they cobbled the donor wing onto his aircraft in such a way that it ended up being longer, due to the damaged spar?

This is just a guess, as I'm not familiar with the P-39's assembly points.
Very short centre section and each outer panel is attached with 8 spanwise bolts in bathtubs each side of the spar as shown in the photo below. This is common to all post prototype aircraft.

Some of you will have seen this photo in the venerial Darby's book captioned one of the authors salvage jobs. The venerial one was not in Papua New Guinea when I did this salvage and that, and many other photos in his book, was used without credit, acknowledgement or permission. Around half the photos in that book were taken by me or by Ian Whitney who likewise was never credited. I made the mistake of employing him about a year after this photo was taken to assist me. Not my smartest move. This is from a 1973 publication where I did supply the photo and was credited.

1655154420804.png


I have just sent the 8mm film of this project for digitization and, if it is good enough, will publish it on line on Vimeo and maybe the Internet Archives Video Section.
 
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MiTasol

Chief Master Sergeant
3,987
4,924
Sep 19, 2012
I dont think his parachute is going to be much use from there unless they made MAJOR changes to the side cowls.
 

Dr. Odendahl

Recruit
6
3
Dec 10, 2016
There were 2 "XP"-39Es built with squared off wingtips. 35 feet 10 inches. One crashed during a spin test (Imagine that!)

Not likely - that would change the configuration of the aircraft and unless it was a matter of life or death (which "could have" happened on the canal) I see no maintenance officer in their right mind to allow an aircraft to fly outside of SRM specifications unless they got authorization from the factory.

I see this whole story as a myth - all production models of the P-39 maintained the same wingspan. There might have been a repair tolerance in the SRM that allowed some deviation but this would be negligible. For the time it would take to repair a wing, it would be easier to install a whole new one. The following shows a P-39 being assembled in the field. You can see how the wing is installed.

This story sounds like a "Cadinism"


Cool film.
 

MIflyer

1st Sergeant
4,563
6,954
May 30, 2011
Cape Canaveral
The drive shaft doesn't seem to be installed. Not much padding on the front seat to keep the passengers butt separated from the drive shaft.
Edwards Park reported that firing the cannon jostled the drive shaft, which gave you a bit of a prostate massage, making the business of shooting at people oddly sensual. So that's a feature, not a bug.
 

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