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

[vikingBerserker]

Who keeps deleting my "P-39 vs F-35" thread????????

 

[Marcel]

There are so many P-39 threads that I simply can't keep up.

Yeah, it even made me change my title.

 

[GrauGeist]

And for the record, this was the only Cobra that Bell made, that was a true winner...

 

[Marcel]

I was wondering if the P39 could have done the first flight better than the Wright Flyer I?

And when will Singapore Airlines replace it's A380 fleet with a bunch of re-engined P39s?

 

[DerAdlerIstGelandet]

I went back to page 62, after finding that the thread name was changed, and put in a couple of pics of the P-63A engine compartment. Just FYI.

I compliment the moderators in consolidating the P-39 comments into this thread. Now we can simply ignore it going forward if we like. I like that option.

Cheers.

It may have screwed up the order of things, but I will be honest I don't care. There is no need for multiple P-39 threads all saying the same repeated stuff over.

 

[DerAdlerIstGelandet]

Thread title updated to a more accurate one.

 

[fubar57]

Website updated to a more accurate one...https://p-39groundhog ad nauseam/forum/

 

[P-39 Expert]

OK guys, I went into the museum today to work on the Grumman Mallard cowling and looked at both the P-39 and the P-63 while I was there.

There is a virtual plug in the P-63A behind the wing root training edge where the auxiliary supercharger goes and it has a cross member in it on which to mount the aux-stage supercharger. The area has plenty of room for the aux-stage A/C. The wing is moved back on the fuselage to balance the CG. The aux-stage supercharger is almost as wide as the engine itself. The P-39 does not have the plug and there is no room for the auxiliary-stage supercharger since the fuselage is more narrow than the auxiliary-stage supercharger itself.

A 2-stage Allison just will NOT fit. The engine compartment is virtually the same since both of them mounted the same engine block, but there is simply not room on the P-39 for the second stage and coupling. Granted, you could MAKE room, but you'd have to insert a plug to make room and then move the wing aft to make the CG possible ... and you'd have a P-63.

I have some pics of the P-63 and will come back here and insert same within a few days, but there is no way to mount a 2-stage Allison in the P-39 in a stock airframe. There is room for the engine, but not for the aux-stage S/C. If you disagree with that, I suggest you come look at them both in Chino, CA for yourself. If you come to see, let me know and I'll happily show you around so you see for yourself. If you are close then, by all means, PM me and I'll show you around. If you aren't close, you are welcome anyway but you'll be wasting your money if the trip is just to address this subject. The engine package for the 2-stage Allison just will not fit and, if it did, the resulting airplane would be out of CG aft without lead ballast in the nose or moving the wing aft to compensate.

I do NOT have too many pics of the P-39 because, to get the pics I need, I'd have to take off several panels from the P-39, and it is in a very good display and there is no real reason to do any disassembly when there is useful work to be done. There are enough P-39 pics available already. The cross-section of the P-39 fuselage just aft of the engine compartment narrows very quickly to the point where is simple to observe that the aux-stage will not fit. Casey Wright (currently working on the P-63) said that he has looked and said: 1) there are things in the way where the aux-stage would go, 2) there is no way to mount the aux stage, and 3) the fuselage is just too small where the aux stage would physically need to be.

Here is a P-39:
View attachment 624074

Look at the relative length of the nose in front of the wing versus the tail behind the trailing edge. The leading edge of the fin is about the same distance as the nose from the trailing edge. Note the insignia star has no bars and is behind the scoop just a small amount. If the insignia star HAD bars, the bars would extend ahead of the scoop rear edge. Note the engine exhaust manifolds stop just in front of the point where the wing trailing edge would intersect the fuselage. If it HAD an aux-stage supercharger, it would extend past the wing trailing edge to about the rear of the airscoop. The fuselage aft of the exhaust manifolds narrows quickly. Note if you extend the wing leading edge, it intersects the fuselage right about where the windscreen starts.

View attachment 624075

Here is a P-63. Note the insignia star has bars and the bars are still aft of the scoop rear edge. The tail is longer because there is more room behind the wing trailing edge and the engine exhaust manifolds are farther forward from the wing trailing edge. The aux supercharger stage would end about at the wing trailing edge. The fuselage at the end of the exhaust manifolds is about as wide as the engine compartment since the aux-stage goes in there. Note if you extend the wing leading edge to the fuselage it intersects right about the windscreen rear frame is. The wing has been moved aft about a foot or so from where it is on the P-39.

OK, here are some P-63 pics:

View attachment 624129

I apologize for the orientation, it's correct in my phone. I don't know how to rotate the pic in this forum. This is looking down into the "plug" at the rear of the engine bay, where the auxiliary supercharger would be if the engine were to be a 2-stage Allison. The engine installed is NOT a 2-stage, but CAN put out 1,600 hp if asked to do so. This empty space is NOT present in a P-39 and the rear bulkhead is up right against the aft end of the engine block.


View attachment 624130

Above is at least oriented correctly. You can see there is plenty of room behind the single-stage engine for the auxiliary-stage supercharger. This space is not present in the P-39.

All for now; cheers!

 

[special ed]

I have.

 

[Thumpalumpacus]

It may have screwed up the order of things, but I will be honest I don't care. There is no need for multiple P-39 threads all saying the same repeated stuff over.

C'mon now. We need a thread on how a P-39 could do long range escort; we need a thread on how the P-39 would have foiled Pearl Harbor. We need a thread on how the P-39 saved Cairo from Rommel, how it saved Nimitz at Midway, and how it saved GMC when the Great Recession hit in 2009.

Whether I've cleared the statute of limitations for how it helped me rid myself of those pesky spam-callers or not may determine whether I start a thread about its potency in that theater of action. I can only say that the 37mm nose cannon shoots 30 rounds of Spam.

 

[P-39 Expert]

OK guys, I went into the museum today to work on the Grumman Mallard cowling and looked at both the P-39 and the P-63 while I was there.

There is a virtual plug in the P-63A behind the wing root training edge where the auxiliary supercharger goes and it has a cross member in it on which to mount the aux-stage supercharger. The area has plenty of room for the aux-stage A/C. The wing is moved back on the fuselage to balance the CG. The aux-stage supercharger is almost as wide as the engine itself. The P-39 does not have the plug and there is no room for the auxiliary-stage supercharger since the fuselage is more narrow than the auxiliary-stage supercharger itself.

A 2-stage Allison just will NOT fit. The engine compartment is virtually the same since both of them mounted the same engine block, but there is simply not room on the P-39 for the second stage and coupling. Granted, you could MAKE room, but you'd have to insert a plug to make room and then move the wing aft to make the CG possible ... and you'd have a P-63.

I have some pics of the P-63 and will come back here and insert same within a few days, but there is no way to mount a 2-stage Allison in the P-39 in a stock airframe. There is room for the engine, but not for the aux-stage S/C. If you disagree with that, I suggest you come look at them both in Chino, CA for yourself. If you come to see, let me know and I'll happily show you around so you see for yourself. If you are close then, by all means, PM me and I'll show you around. If you aren't close, you are welcome anyway but you'll be wasting your money if the trip is just to address this subject. The engine package for the 2-stage Allison just will not fit and, if it did, the resulting airplane would be out of CG aft without lead ballast in the nose or moving the wing aft to compensate.

I do NOT have too many pics of the P-39 because, to get the pics I need, I'd have to take off several panels from the P-39, and it is in a very good display and there is no real reason to do any disassembly when there is useful work to be done. There are enough P-39 pics available already. The cross-section of the P-39 fuselage just aft of the engine compartment narrows very quickly to the point where is simple to observe that the aux-stage will not fit. Casey Wright (currently working on the P-63) said that he has looked and said: 1) there are things in the way where the aux-stage would go, 2) there is no way to mount the aux stage, and 3) the fuselage is just too small where the aux stage would physically need to be.

Here is a P-39:
View attachment 624074

Look at the relative length of the nose in front of the wing versus the tail behind the trailing edge. The leading edge of the fin is about the same distance as the nose from the trailing edge. Note the insignia star has no bars and is behind the scoop just a small amount. If the insignia star HAD bars, the bars would extend ahead of the scoop rear edge. Note the engine exhaust manifolds stop just in front of the point where the wing trailing edge would intersect the fuselage. If it HAD an aux-stage supercharger, it would extend past the wing trailing edge to about the rear of the airscoop. The fuselage aft of the exhaust manifolds narrows quickly. Note if you extend the wing leading edge, it intersects the fuselage right about where the windscreen starts.

View attachment 624075

Here is a P-63. Note the insignia star has bars and the bars are still aft of the scoop rear edge. The tail is longer because there is more room behind the wing trailing edge and the engine exhaust manifolds are farther forward from the wing trailing edge. The aux supercharger stage would end about at the wing trailing edge. The fuselage at the end of the exhaust manifolds is about as wide as the engine compartment since the aux-stage goes in there. Note if you extend the wing leading edge to the fuselage it intersects right about the windscreen rear frame is. The wing has been moved aft about a foot or so from where it is on the P-39.

OK, here are some P-63 pics:

View attachment 624129

I apologize for the orientation, it's correct in my phone. I don't know how to rotate the pic in this forum. This is looking down into the "plug" at the rear of the engine bay, where the auxiliary supercharger would be if the engine were to be a 2-stage Allison. The engine installed is NOT a 2-stage, but CAN put out 1,600 hp if asked to do so. This empty space is NOT present in a P-39 and the rear bulkhead is up right against the aft end of the engine block.


View attachment 624130

Above is at least oriented correctly. You can see there is plenty of room behind the single-stage engine for the auxiliary-stage supercharger. This space is not present in the P-39.

All for now; cheers!

Man I appreciate all the work you have put into this, but I must respectfully disagree with you. The aux stage SC on the P-63 was in that area just in front of the radio mast in your P-63 photo above. On your P-39 photo above that radio mast (coincidentally) marks the exact same spot, the location of the bulkhead that separates the aux SC from the oil tank. The bulkheads on both planes are exactly the same distance from the front edge of the engine compartment. Both compartments are exactly the same size on each plane. Now some items in the P-39 would need to be moved, mainly the coolant tank, but if the aux SC fit in the P-63 than it would have to fit in the P-39. I have posted Bell drawings that verify this.

Also, the engine compartment does not get narrower until aft of that bulkhead marked by the radio masts. See page 6 of the attached P-39 Weights & Measurements below. The two longitudinal beams that make up the forward fuselage are parallel, they do not get narrower. You are looking aft, the end nearest you is the attachment to the remote reduction gear (where the nose armor is located) then moving aft is the armament bay (sloped area) followed by the cockpit floor followed by the engine bay (the see through part). The aux SC would be located behind/under the beams where they begin to angle back up. The top tip of those beams is mounted to the bulkhead that is just in front of the oil tank and forms the aft end of the engine compartment. As you can see those longitudinal beams run parallel, they do not get narrower. Same amount of room in both planes. If it fit into one it had to fit into the other.

 

[buffnut453]

A far greater quantity of spam has been expended in the various P-39 threads...indeed, the discussion is like a gatling gun which just keeps spinning and spinning....and spinning.

 

[pbehn]

With regard to the answers from pbehn and Peter Gunn, why would one want to divert engines or better engines to the inferior airframe?

Well, not all air frames are the best. By definition there is only one top dog. The P-39 wasnt utter rubbish, it wasnt as good as it was advertised either. Much of the story is about events and logistics as it is about performance curves. By the time The RAF were flying the P-39 with 601 squadron Germany had invaded Russia. Churchill offered the P-39 to the Russians. In the short term the UK probably had more aircraft in crates ready to send than the USA had. In the long term, the P-39 was as good or better than aircraft the Russians had in service but not better than those the RAF already had or would get shortly. Since the P-39 used the Allison it didnt take engines used by the types in US service or projected for the future it didnt affect any part of USA long term plans

There see... not a chart orCoG discussion at all.

 

[P-39 Expert]

Was there ever a P-39 with a gross weight of 5,500lb? Not sure that any of the prototypes even reached that mark. My apology, 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. Ordered before the BoB, completed in 1941 after the BoB.

All your arguments for throwing away armour, IFF, moving radios, ditching guns, etc, only brings the weight down to 7,150lb to 7,250lb according to your estimations. What happened to the other 1,600+lb? The 7150lb weight is for a P-39D without wing guns and the nose armor (AHT).

Perhaps if you throw out all the armour, all the guns and ammo you may get close. But what use is that? Only the reduction gear armor deleted. All the other armor remains including the armor plate in front of the pilot, on the windshield, aft of the pilot, aft of the oil tank and the armored glass in front of and behind the pilot's head. Only the 30cal wing guns deleted, the cannon and two 50cal machine guns remain. The 30cal guns didn't pack any punch and their effective range was only 200yds (AHT). The 7150lb P-39D was a fully equipped warplane with self sealing fuel tanks, pilot armor and cannon and heavy machine gun armament.

Also, since you are arguing that the British should have had the P-39 without the "extra weight", the IFF should definitely stay. Because the British had radar and their aircraft had IFF. Yes the British specified an IFF radio and yes they did have radar. But they didn't use their P-400s. The P-39 in 1942 was used in the Pacific at Port Moresby which didn't have radar until late 1942. So IFF was useless until radar was installed. Any more exaggerations I can help you with?

 

[buffnut453]

Also, the engine compartment does not get narrower until aft of that bulkhead marked by the radio masts. See page 6 of the attached P-39 Weights & Measurements below. The two longitudinal beams that make up the forward fuselage are parallel, they do not get narrower.

You cannot say that with certainty unless you have width measurements for the relevant stations. Drawings and schematics are merely representations of reality. You need detailed measurements for bulkheads, to include radii for any curves etc.

 

[FLYBOYJ]

The P-39 in 1942 was used in the Pacific at Port Moresby which didn't have radar until late 1942. So IFF was useless until radar was installed.

From what I'm seeing the P-39s that were based at Port Moresby didn't have IFF installed in them to begin with. If you have information that says otherwise, I'm all ears.

 

[Thumpalumpacus]

One cannon and two .50s ain't really a suitable armament suite for 1942-43 in a plane that is struggling to keep up on performance parameters as well. Add in short range and limited altitude performance, meh.

There's a reason it was passed over. That was that it didn't deliver on promise.

 

[P-39 Expert]

From what I'm seeing the P-39s that were based at Port Moresby didn't have IFF installed in them to begin with. If you have information that says otherwise, I'm all ears.

Per AHT the P-39D models did not, the P-400, D-1, D-2, K and L did. The IFF sets may have been added later to the D.

 

[pbehn]

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. Ordered before the BoB, completed in 1941 after the BoB.

This is utterly preposterous, it wasnt "the British" that changed the requirements it was the war, armour was put in planes not designed for it all over the world. The Spitfire doubled in weight for all sorts of reasons. Show me a any protest from North American discussing the P-51 about fitting more fuel inside and outside, more guns, tail warning radar, making it a dive bomber etc etc etc.

 

[FLYBOYJ]

Per AHT the P-39D models did not, the P-400, D-1, D-2, K and L did. The IFF sets may have been added later to the D.

Well it's kind of funny because IFF units were classified equipment and as mentioned several times had a destruct system built into them should a crash insure and the pilot survive. I believe in the emergency procedures in one of the P-39 flight manuals mentions activating the system if the aircraft was ever downed, so with that said I doubt that any P-39 or P-400 flying around Port Moresby had an IFF unit installed if no radar was available.