Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)

[P-39 Expert]

Thanks Biff - but OH, LOOKIE HERE!!!

"The weight distribution of the P-39 was supposedly the reason for its tendency to enter a dangerous flat spin, a characteristic Soviet test pilots were able to demonstrate to the skeptical manufacturer who had been unable to reproduce the effect. After extensive tests, it was determined the spin could only be induced if the aircraft was improperly loaded, with no ammunition in the front compartment. The flight manual noted a need to ballast the front ammunition compartment with the appropriate weight of shell casings to achieve a reasonable center of gravity."
Reply: This is saying that with the spent shell casings still in the front fuselage would achieve a reasonable center of gravity.

Dean, Francis H. America's Hundred Thousand P 200

So with that said, do you think anyone in their right mind would want to remove the 70 pounds of armor from the gear box????

To save 70lbs of weight. The plane could easily be balanced by moving or removing the IFF radio. And the plane entered the spin with no ammo in the nose. But the weight of the spent shell casings still in the nose would achieve a reasonable center of gravity. Not likely to go into combat with no ammunition in the front compartment.

 

[FLYBOYJ]

To save 70lbs of weight. The plane could easily be balanced by moving or removing the IFF radio.

And I showed you over and over that if you do this you're still AFT in the CG ENVELOPE!!!

and...you keep saying the Soviets REMOVED their IFF - THEN WHY DIDN'T THEY REMOVE THE GEAR BOX ARMOR???? PLEASE ANSWER THIS QUESTION?!?!?

And again - you "balance" see-saws and spinning plates.

And the plane entered the spin with no ammo in the nose. But the weight of the spent shell casings still in the nose would achieve a reasonable center of gravity.

Not with 70 pounds of armor removed!!!!

Oh - the cannon shell casing mod - WHY WAS THAT DONE? APPARENTLY THE SOVIETS SHOWED THE NEED FOR IT!

Not likely to go into combat with no ammunition in the front compartment.

No, but you're hopefully gonna fly home that way LOL!!!!!

 

[FLYBOYJ]

That's odd, isn't Bell still to this day supplying aircraft to all four services?

Not fighter aircraft - "Bell Helicopters" Larry Bell and his exaggerations, if not flat out lies put an end to that!!!!

 

[GregP]

Bell is still supplying aircraft to the U.S. Government, just not fighter aircraft. Their last fighter made in any numbers was the P-63, though they DID make one XP-77 and two XP-83s.

Oops FBJ, saw your post when I posted this. Nevermind ...

 

[buffnut453]

Other than the CofG problem, would a weight reduction of just 1/100th of the gross weight result in any substantive performance improvements? Given that the performance within a production batch of "identical" airframes can change by +/-5% (or perhaps even more), removing 70lbs is kindda in the noise (IMHO).

 

[FLYBOYJ]

Other than the CofG problem, would a weight reduction of just 1/100th of the gross weight result in any substantive performance improvements? Given that the performance within a production batch of "identical" airframes can change by +/-5% (or perhaps even more), removing 70lbs is kindda in the noise (IMHO).

And keeping it in place moves the C/G forward over 2 inches in some configurations!!!

 

[pbehn]

To save 70lbs of weight. .

You cannot call 70lbs "weight" without some risk of terminological inexactitude. It may be enough to change a CoG calculation but is probably less than the difference between the heaviest and lightest pilot. Work it out in terms of gallons of fuel coolant and oil.

 

[Glider]

So when did this cleaned up Typhoon actually enter combat?

It was a standard production fit from Nov 43 and conversion kits were produced so aircraft could be modified in the field. There was as you would expect a transition period, and just by looking at photographs, its rare to find a photo of the old 'car door' version after March/April 44. I have a couple of photo's of squadrons in flight dated March 44 in my book on the 2TAF and both versions are in both photo's
I wouldn't be surprised if there wasn't a push to get it as a standard equipment for the invasion, but cannot guarantee that.

 

[P-39 Expert]

" I just looked it up and the exact weight is 5849lbs gross per the contract signed in Feb 1940. This weight was the basis for the 400mph estimates, aka P-400. Final gross weight after the British finished with it in 1941 was 7850lbs"


Hmm, strangely enough, the P-39C went 5,070lbs empty, 7075lbs gross weight (combat) and 7300lbs max gross. They were ordered August 10th 1939. So, in Feb of 1940, 6 months later Bell is telling the British the plane will only weigh 5879lbs gross for combat?
809lbs useful load? The P-39C may have been ordered in August 1939 but the first production delivery was in January
160lb pilot (including 20lb parachute) 1941 and it suffered substantial weight gain during production like the P-400. The weight specified
290lbs just for the .50 cal guns and ammo on the contract was substantially lower, more like the original P-400 weight.
45lbs of oil (2 gallons for the gear box and only 4 gallons for the engine)

Leaves us about 70 gallons of gasoline and no gun sight.

There was absolutely no way Bell could have delivered a usable fighter aircraft even without armor or protected tanks with a gross weight of 5849lbs, regardless of what the British did.

On Sept 13th 1940 the USAAC ordered a bunch of P-39Ds and changed the contract for the 21st through 80th P-39C to P-39Ds with protection and wing guns.
From Joe Baugher's website on the P-39D page.
Weights: 5462 pounds empty, 7500 pounds gross, and 8200 pounds maximum takeoff.

Want to tell us in detail just what those perfidious sons of Avalon specified in the P-400s that the US was not specifying in the P-39D? Okay, in detail (AHT) the P-39D weighed 5523lbs empty and grossed 7690lbs. The P-400 weighed 5550lbs empty and grossed 7700lbs even. You can look for the 10lb difference if you like.

Please expand above.

 

[pbehn]

Please expand above.

Why didnt Bell supply the Russians nice light planes without the impositions of Perfide Albion?

 

[P-39 Expert]

The range of the P-39 was half that of Navy fighters.
The F4U's range was 1,000 miles.
The F6F's range was 945 miles.
The F4F's range was 845 miles.
And even the SBD's range was 1,100 miles.
All these ranges are with internal fuel and combat loads - the ferry ranges were further.
And every single aircraft listed above operated from carriers during the war.

Please produce your source on those ranges, but they computed range differently than the AAF. Computed the army way with the appropriate takeoff and climb allowance, cruise out at high altitude, 20 minutes of combat and cruise back at high altitude with the appropriate reserve for landing the ranges were very close.

 

[FLYBOYJ]

Why didnt Bell supply the Russians nice light planes without the impositions of Perfide Albion?

WHY DIDN'T THE RUSSIANS REMOVE THE GEAR BOX ARMOR!

 

[P-39 Expert]

WHY DIDN'T THE RUSSIANS REMOVE THE GEAR BOX ARMOR!

Obviously they chose not to, for whatever reason. I never said that anyone ever removed the gear box armor. It's just an idea. But if they did, appropriate measures could be taken to keep the plane within the CG limits. That's all I have ever said. And you really can't argue that point.

 

[FLYBOYJ]

Please produce your source on those ranges, but they computed range differently than the AAF. Computed the army way with the appropriate takeoff and climb allowance, cruise out at high altitude, 20 minutes of combat and cruise back at high altitude with the appropriate reserve for landing the ranges were very close.

Tell you what - let's see YOU calculate the maximum P-39 range (any model you want) "with the appropriate takeoff and climb allowance, cruise out at high altitude, 20 minutes of combat and cruise back at high altitude with the appropriate reserve for landing."

 

[FLYBOYJ]

Obviously they chose not to, for whatever reason. I never said that anyone ever removed the gear box armor. It's just an idea. But if they did, appropriate measures could be taken to keep the plane within the CG limits. That's all I have ever said. And you really can't argue that point.

And you're arguing a hypothetical idea that was clearly shown WHY it shouldn't be done, this based on historical records to show both the P-39 AND P-63 had aft C/G issues clearly identified by the Soviets!!!!

 

[P-39 Expert]

I almost hate to chime in on this thread anymore but smart decisions are not my forte.

RE: 37mm cannon.

Waaaay back in the dark ages of the 1970's when I was still in GA and was the dumb kid working at the airport I knew a fellow that would come out every so often to fly. He had been an actual honest to Yeager P-39 pilot in the SWP. The one tidbit I remember was how much he disliked the 37mm cannon for anything other than landscaping. The trajectory was terrible he said, like a rainbow. It fired too slow and he couldn't hit anything with it in the air, he did however favor it for shooting up Japanese barges and small craft on the water. He related that one time he put a 37mm round into a barge carrying troops, he said it rattled around like a pinball in a bathtub and made a real mess. It was one of the times he threw up in the cockpit. I can only imagine what that did to human flesh and bone... ugh.

I see a lot of balloon juice here about how magnificent the 37 was for firepower, strange that a real pilot who flew it in combat did not think so. I'm sure someone will be happy to refute this with a chart or a graph or some such drivel showing how wrong my old friend was.

Fortunately he survived his time in the P-39 (his words btw) and his next assignment to a front line squadron was with his true love, the Cadillac of the Skies.

Also, regarding another post up thread, the air war was won by the time the P-51D arrived? News to me.

Also regarding the P-39 being a "beast down low", I think Buzz Wagner would disagree with you.

The cannon was always an enigma. The P-39 was the only AAF plane that used it. From what I have read the combat pilots were split about 50/50 vs. the alternate 20mm cannon in the P-400 and P-39D-1. The 37mm advocates liked its destructive power, the 20mm men liked the longer range and higher rate of fire. Personally I think I would have preferred the 20mm for the same reasons plus the lower weight.

 

[Thumpalumpacus]

Interesting points FBJ. The number 1 customer goes to the manufacturer, is initially ignored, but later proves his point to such an extent that changes are made (moving the CG FORWARD) of version 2.0 of the Cobra. With all that Bell knew about the P-39 it's interesting to see what they initially got wrong on the P-63. It's almost as if they thought they were smarter than the user. And looking at Bell through that perspective might give one pause.

Cheers,
Biff

I think one reason why Grumman, Boeing, and other companies stayed in business while Brewster and Curtiss did not is exactly this: listening to the end users, and putting those mods into place efficiently.

There are, of course, other factors as well -- Brewster's shoddy workmanship, Curtiss' designs being regularly a year or two behind cutting-edge -- but you get my point.

ETA: I edited this post to remove Bell from the list of has-beens because they did of course do good work on heloes for decades after WWII.

 

[GrauGeist]

Please produce your source on those ranges, but they computed range differently than the AAF. Computed the army way with the appropriate takeoff and climb allowance, cruise out at high altitude, 20 minutes of combat and cruise back at high altitude with the appropriate reserve for landing the ranges were very close.

You're the expert - look it up yourself.

 

[FLYBOYJ]

Personally I think I would have preferred the 20mm for the same reasons plus the lower weight.

Along with gear box armor and ballast in the nose!

 

[Thumpalumpacus]

And the plane entered the spin with no ammo in the nose. But the weight of the spent shell casings still in the nose would achieve a reasonable center of gravity. Not likely to go into combat with no ammunition in the front compartment.

But more likely to experience that circumstance at the end of a mission, slowing and turning on approach. A crashed plane is a crashed plane, and a low-altitude stall is a bitch.