GregP
Major
Hi P-39 Expert, let me try once here.
I am a volunteer at the Planes of Fame Museum in Chino, CA. We have a P-39 (static) and Fighter Rebuilders is located onsite, owned by Steve Hinton and son. They have built up a P-39 on at least one if not more occasions and I have looked pretty closely at the static P-39. None of what I am saying here is from Fighter Rebuilders or the Museum, it is my observations only. I mention the above only so you know that WWII fighters are very much present there all the time, not just on occasion. They operate WWII fighters VERY regularly, even several times per week ... that is ... pre-COVID anyway.
There isn't a lot you can remove from a P-39 that is not structural or in the wrong place, CG-wise, for removal. If you remove the nose guns, I assume you remove the ammunition, too. You have to do something to keep in CG. If you remove the nose guns, except the cannon, the ammunition, and the nose armor plate, the airplane WILL be lighter, but you can't fly it since the CG is out of limit aft. There is NOTHING heavy in the tail cone except maybe the radio, and nobody was going to let their radio be deleted. They might need it to communicate where they ditched in the ocean, if for nothing else. It wasn't going to "go away" without the pilots rebelling.
So, I fully support your contention that lightening the P-39 would have been a good thing. I'm just having a hard time trying to decide WHAT to delete that would make a difference while remaining flyable and maintaining combat effectiveness. See the image below.
The cutaway below is an early P-39 and had 30-cal guns, but later variants had 50-cal guns. I'll assume 50-cals.
The only thing I see that is removable behind the center of gravity, which is about 1/3 of the way back from the wing leading edge, is the radio receiver (#12 above), and it ain't going anywhere. The pilot's back armor is #28 above, and is about right on the CG (18.2 pounds). Most pilots would not remove it even though the engine is a pretty good armor by itself. You might remove the #74 wing guns (145 pounds) and #79 ammunition (186 pounds), but what else can you suggest that would effect a significant weight change aft of the CG? I may be blind, but I don't see it. There is no significant structure to get rid of.
If you DO remove the wing guns, you are lighter by 331 pounds but you also have only a cannon that jams easily and has few rounds anyway and two 50-cal nose guns. This ain't no German MG 151/20, it's an Oldsmobile jamming fool and, if it DOES jam, you are down to two 50-cal MG ... just mildly better than what a P-26 Peashooter had. I'd rather leave the armament, operate the engine beyond recommended limits for better performance, and play fighter below 12,000 - 15,000 feet.
You might only remove ONE gun (the outer one) and ammunition in each wing, and you'd save 165 pounds or so. But, is that going to make your airplane a noticeably-better fighter in a dogfight against your likely opponent? I think not. It might climb marginally better, but not enough to catch a Zero by LONG shot. The Zero had more than a little better climb rate at P-39 combat altitudes.
Kick me if you can see it differently, but all the structure behind the wing trailing edge seems necessary for flight and structural integrity to me.
I'd not remove the #17 oil tank armor for any reason whatsoever.
I am a volunteer at the Planes of Fame Museum in Chino, CA. We have a P-39 (static) and Fighter Rebuilders is located onsite, owned by Steve Hinton and son. They have built up a P-39 on at least one if not more occasions and I have looked pretty closely at the static P-39. None of what I am saying here is from Fighter Rebuilders or the Museum, it is my observations only. I mention the above only so you know that WWII fighters are very much present there all the time, not just on occasion. They operate WWII fighters VERY regularly, even several times per week ... that is ... pre-COVID anyway.
There isn't a lot you can remove from a P-39 that is not structural or in the wrong place, CG-wise, for removal. If you remove the nose guns, I assume you remove the ammunition, too. You have to do something to keep in CG. If you remove the nose guns, except the cannon, the ammunition, and the nose armor plate, the airplane WILL be lighter, but you can't fly it since the CG is out of limit aft. There is NOTHING heavy in the tail cone except maybe the radio, and nobody was going to let their radio be deleted. They might need it to communicate where they ditched in the ocean, if for nothing else. It wasn't going to "go away" without the pilots rebelling.
So, I fully support your contention that lightening the P-39 would have been a good thing. I'm just having a hard time trying to decide WHAT to delete that would make a difference while remaining flyable and maintaining combat effectiveness. See the image below.
The cutaway below is an early P-39 and had 30-cal guns, but later variants had 50-cal guns. I'll assume 50-cals.
The only thing I see that is removable behind the center of gravity, which is about 1/3 of the way back from the wing leading edge, is the radio receiver (#12 above), and it ain't going anywhere. The pilot's back armor is #28 above, and is about right on the CG (18.2 pounds). Most pilots would not remove it even though the engine is a pretty good armor by itself. You might remove the #74 wing guns (145 pounds) and #79 ammunition (186 pounds), but what else can you suggest that would effect a significant weight change aft of the CG? I may be blind, but I don't see it. There is no significant structure to get rid of.
If you DO remove the wing guns, you are lighter by 331 pounds but you also have only a cannon that jams easily and has few rounds anyway and two 50-cal nose guns. This ain't no German MG 151/20, it's an Oldsmobile jamming fool and, if it DOES jam, you are down to two 50-cal MG ... just mildly better than what a P-26 Peashooter had. I'd rather leave the armament, operate the engine beyond recommended limits for better performance, and play fighter below 12,000 - 15,000 feet.
You might only remove ONE gun (the outer one) and ammunition in each wing, and you'd save 165 pounds or so. But, is that going to make your airplane a noticeably-better fighter in a dogfight against your likely opponent? I think not. It might climb marginally better, but not enough to catch a Zero by LONG shot. The Zero had more than a little better climb rate at P-39 combat altitudes.
Kick me if you can see it differently, but all the structure behind the wing trailing edge seems necessary for flight and structural integrity to me.
I'd not remove the #17 oil tank armor for any reason whatsoever.
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