XP-39 II - The Groundhog Day Thread

[Juha3]

According to "Soviet Air Power in World War 2" by Yefim Gordon
Page 446: The North Fleet Air Arm removed the wing guns along with some armor from their Mk 1s so it could match the Bf 109F-4/G-2/G-4 as well as the Soviet Lagg 5 and Yak-9s

Yes but he continues: "Still, most aircraft were delivered unmodified". The North Fleet Air Arm removed the wing guns along with some armor from their Airacobra Mk Is after lightening tests in late 1942.

Page 447 P-39Q (along with the N version were the most numerous P-39s in Soviet Service) had the wing guns removed and replaced with 2 x 0.50 in pods.
..and of course the P-63s didn't have them either.

Not sure of that covers the vast majority however.

Yes, but there was no need to remove the .30s from Qs because they never had them. Qs were in essence Ns with .5 gunpods instead of .3 wing guns.

 

[Juha3]

Same book on Page 434 listing the Imported aircraft in inventory as of May 1st, 1945 shows 84% of the 2,272 P-39s still in service had no wing guns.

In the list (L-L aircraft in VVS KA 1 May 1945) I have 84% of P-39s are Qs without any mention have they their gunpods still installed or not. And strangely no Ns, besides Qs only Ks, L,s Ms, Ds, D-1s and D-5s. VVS KA had Ns at that time, probably included in Qs, i.e. late production P-39s, because Ks, Ls and Ms (mid-production) are one group and Ds, D-1s and D-5s (early production) another.

 

[XBe02Drvr]

I know at least the Aeroproducts prop on the P-39Q (V01710-89) had full feathering, and I think the Curtis Electric on the P-38J (V-1710-89/91) has full-feathering, though I'm not sure if that was the same Aeroproducts and Curtis props as fitted to the earlier P-39s. But I suspect even the XP-39 had feathering capability seeing as Curtis had props with full feathering as early at least as 1937

What sense does it make to put a full feathering propeller on a single engine airplane? It has very little utility other than to stretch the glide for a dead stick landing, and is one more thing that can go catastrophically wrong. A failed liquid cooled engine will most likely seize up anyway, solving the wind milling problem. Now if they are only manufacturing a single version for singles and twins both, it would make sense to install "aftermarket" high pitch stops on the props for singles, as the last thing in the world you want is for a runaway pitch motor to drive it into feather when you're pulling WEP or other high power setting. Something's going to come unglued, probably spectacularly. Far more disastrous on a single than on a multi.
If you're going to feather a prop, you have to have some way of unfeathering it. An electric prop whose pitch motor has locked itself at the feather end of its travel is going to have to be dismounted and disassembled to be recovered, which may be awkward to impossible, depending on where the plane came to rest after its debacle, and if it's even salvageable.
FIE on electric props!! Bad idea! That's not bigotry, that's fact!

PS: Now I get it. The fluid coupling in the P39's drive train would allow the prop to windmill even if the engine is seized. My apologies for the rant above. Electric props are still a bad idea!

 

[wuzak]

PS: Now I get it. The fluid coupling in the P39's drive train would allow the prop to windmill even if the engine is seized. My apologies for the rant above. Electric props are still a bad idea!

What fluid coupling?

The P-63 had a fluid coupling - in the auxiliary supercharger drive system.

 

[vikingBerserker]

Yes but he continues: "Still, most aircraft were delivered unmodified". The North Fleet Air Arm removed the wing guns along with some armor from their Airacobra Mk Is after lightening tests in late 1942.

Delivered unmodified after which the North Fleet Air Arm removed them is how I read it based on the statement the North Fleet Air Arm removed them in that same section

Yes, but there was no need to remove the .30s from Qs because they never had them. Qs were in essence Ns with .5 gunpods instead of .3 wing guns.

Your question was "Have you any proof that the .30s were deleted on the vast majority of Russian P-39s?" Were you asking about the P-39's in Russian service or if Russia removed them theirselves? If in total then at least as of this date the answer would be yes. If you're asking fi the Russians removed them I could only find in the book where the North Fleet removed them.

In the list (L-L aircraft in VVS KA 1 May 1945) I have 84% of P-39s are Qs without any mention have they their gunpods still installed or not. And strangely no Ns, besides Qs only Ks, L,s Ms, Ds, D-1s and D-5s. VVS KA had Ns at that time, probably included in Qs, i.e. late production P-39s, because Ks, Ls and Ms (mid-production) are one group and Ds, D-1s and D-5s (early production) another.

I did think it was odd that N's were not listed, however off in the far right column listed over 2,000 having been lost. When that is added to what was listed on being on hand in that same chart it comes close to the total accepted by Russia (I dont have the book in front of me, but it was one of the first pages in this chapter). Still, it would be odd that none were in service unless converted and I did not see any mention of it. In regards to the 0.50 pods, the question was about the removal of the 0.30 guns in the wings and I assume the pods could be removed and used as needed, like bombs in a bomb rack.

 

[XBe02Drvr]

What fluid coupling?

The P-63 had a fluid coupling - in the auxiliary supercharger drive system.

My bad! Short circuit in the memory banks. Wrong airplane, wrong location. Not at peak efficiency at 0500.

 

[Peter Gunn]

Just because someone here says I don't understand something doesn't mean that is true. I understand WB and CG as well as the next person on here. It's not brain surgery. Just because you know something doesn't mean someone else doesn't know it also. Also my explanation of critical engine was perfectly acceptable as was shown be subsequent posts by other posters.

I have never once in all my posts on this board EVER told another poster that they didn't know what they were talking about. Not one time. And I have never been snarky with anyone on here that did not get snarky first. And even then they had to be pretty darn snarky for a good while.

I'm not a pilot nor a mechanic. But I can read and I do have an interest in this subject. If pilots and mechanics are the sole and final authority on planes from 75 years ago, then so be it. If quoting valid reference materials is not adequate research, then so be that also.

Hey man, I see where you're coming from but allow me to share.

I was born and raised on the family airfield, my dad and his brothers came back from WWII and turned the family farm in lower Michigan into a bona fide grass strip. We had two runways, four hangars, two of them quite large, repair shop with a mechanic and a pilots lounge. By the time I was 12 I probably spent more time in a Cessna than on my bicycle. (Although I haven't flown since 1978, but that's another story)

As a young lad I couldn't read enough about aerial combat from WWI - Korea, my book knowledge of ACM was essentially "attack from the sun, when bounced, turn into the attack, if in trouble dive away".

I haven't gone near a GA aircraft in decades, but what you can learn and discuss here makes me feel like I never left the GA world.

So when I found this place you can imagine how happy I was to find like minded (and VERY knowledgeable) fellows that are not only cordial, but go out of their way many times to help answer questions and share their years of experience and knowledge.

Why do I blather on like this? Because after YEARS of nothing but book learning, imagine again how exciting it was to learn that here I could actually talk to an F-15 pilot, I give BiffF15 (with two "ffs" + 1) a little razzing every now and then but it's all in good fun and he knows it. But when he discusses ACM I listen and when in doubt ask questions, some of them may be dumb but I don't let ego get in the way of learning.

Or drgondog my love of the P-51 is borderline fanatical, to get to ask questions and receive correct answers on a subject near and dear is simply outstanding, especially the minutiae he can come up with.

I have only illustrated two out of MANY here that you can learn from, I'd list them all but I don't want to leave anyone out and I think you already know who they are anyway.

I like you, you have proven you have knowledge and integrity, as I said before, it isn't easy to stay civil when your arguments are being refuted from all comers, but for the most part I believe you have kept the snark to a minimum and that speaks very highly of you. I doubt I could say the same for me in the same situation, just read my sig line...

In the end, I just wanted you to know that I think highly of what you know, just dial it back a bit and LISTEN to what these guys are saying, I'd NEVER question Wes ( X XBe02Drvr ) on what a critical engine may or may not be. He has age, wisdom and experience... well mostly age, which I respect.

I still think you are a valuable addition to the community here and can make valid contributions to our discussions, just my opinion but remember, my contribution here is just snark and dumb questions so take that for what it's worth.

 

[Ivan1GFP]

My Stepdad always tasked me with loading the drum for his Thompson.
Yeah, there was a winding key on it, but one slip while sticking a .45 round in and there goes your thumbnail.
I much preferred the stick mags...

Hello GrauGeist,

That should not have been so dangerous from what I remember.
The procedure was to put the drum on a flat surface and unlatch and remove the cover plate to load the 50 rounds.
We never loaded less than 50. After that, the cover plate was latched back in place.
You don't touch the winding key while loading rounds in the magazine. It is on the cover plate which is not installed.
Without any spring tension, the rounds are just dropped into the appropriate compartments each of which holds about 5 rounds between the spokes of the drive mechanism.
We never wound up the spring in the Drum until we were ready to shoot it because it is not possible to unwind the drum and storing it with a spring under tension wasn't a good idea.
I don't remember how much to wind the drum but it was stamped on the 50 round drum.
Never wind an empty drum.....

The biggest problem we had was that the Thompson we were using was a semi-auto which fired from a closed bolt.
Getting the empty Drum out was a B*TCH.
On a regular full auto Thompson, it was easy:
Pull back the bolt as if you are about to fire and it will lock back.
Then activate the magazine catch with one hand and slide out the Drum with the other....
On a semi, the sear doesn't lock the bolt back.
The Drum also does NOT activate the bolt stop like regular stick magazines do.
You can't reach the bolt stop with the Drum in place.
You need to hold the bolt back with one hand to keep it out of the track of the Drum,
Activate the magazine catch so the Drum can slide out of the gun,
Use your THIRD hand to slide the Drum out of the gun.

Stick Magazines were so much easier but had other problems.
The Receiver of a semi Thompson is not quite as deep as a full auto Thompson.
As a result, the Stick Magazines do not go in as far.
What some people do is re-grind the hole in the magazine that the Magazine Catch goes into so that it still latches.
I always thought this was a stupid idea because it meant that new Stick Magazines would not work until modified.
On this gun, we modified the Magazine Catch so that an unmodified Stick Magazine would fit.
Of course that meant that the Stick Magazines that came with the gun would not work any more.
Brand new Stick Magazines were not hard to find at the time and were not expensive either.

There was one other interesting problem with the Thompson Carbine.
It would NOT run on commercial .45 ACP ammunition.

Military .45 Auto ammunition out of a 5 inch M1911 type is spec'ed at 830 fps or 850 fps with a 230 grain bullet.
The commercial 230 grain ammunition typically gets only about 805 fps and sometimes as low as 780-790 fps average on a chronograph.
That wasn't enough to reliably cycle the bolt of the Thompson with its much heavier springs. Military ammunition worked pretty reliably though.
The longer barrel on the semi auto Thompson also gave considerably higher velocity with the same ammunition. Typically, military ammunition was getting pretty close to 100 fps higher than what it was doing in a 5 inch M1911.

- Ivan.

 

[pinsog]

That .375 Ultra Mag sounds like a bit of overkill for deer? I only have perhaps two rifles that are suitable for deer in this area though I don't hunt and have never hunted (unless you count insects). Just about everything else is a heavy scoped gun or collectible (to me) or service rifle type. My preference is mostly .308 semi autos these days.
My Wife recently got into bicycling and commented that the plastic valve stem cap on one of my Daughter's bikes had disintegrated.
I told her that those caps were probably almost two decades old so it wasn't surprising. They were salvaged along with metal caps from valve stems that I sometimes found when processing wheel weights for cast bullets. I literally went through hundreds of pounds of wheel weights back then for black powder guns, .45-70 and pistols. Lead doesn't actually go far when you are only getting about 14-15 bullets per pound.

- Ivan.

I had my 375 ultra mag built for a trip to Africa back in 2005. Sako action, McMillan stock, Schneider match grade barrel. It's a tack driver. My son started shooting it at 13 years old, took it away from me and killed his next 14 deer with it. He was 14 and my brother was teasing him about something and my son looked at him and said "well at least I don't hunt with a woman's gun". My brother was hunting with a 3006. I about wet my pants laughing. I had a 375 built for my son when he was 14, turned out a bit heavy so he carried mine until he got bigger. We are shooting 260 grain Nosler Accubonds at 2900 feet per second. We don't have to track wounded deer that's for certain...

 

[Juha3]

Delivered unmodified after which the North Fleet Air Arm removed them is how I read it based on the statement the North Fleet Air Arm removed them in that same section




Your question was "Have you any proof that the .30s were deleted on the vast majority of Russian P-39s?" Were you asking about the P-39's in Russian service or if Russia removed them theirselves? If in total then at least as of this date the answer would be yes. If you're asking fi the Russians removed them I could only find in the book where the North Fleet removed them.




I did think it was odd that N's were not listed, however off in the far right column listed over 2,000 having been lost. When that is added to what was listed on being on hand in that same chart it comes close to the total accepted by Russia (I dont have the book in front of me, but it was one of the first pages in this chapter). Still, it would be odd that none were in service unless converted and I did not see any mention of it. In regards to the 0.50 pods, the question was about the removal of the 0.30 guns in the wings and I assume the pods could be removed and used as needed, like bombs in a bomb rack.

I'm not a native English speaker, but the quote is: "The North Fleet Air Arm followed these recommendations and reduced the P-400's weight by 247 kg. Still, most aircraft were delivered unmodified." I read that that the North Fleet Air Arm removed wing guns but most other commands did not. IMHO all P-400s and P-39Ds - Ns arrived to the USSR with wing guns as did most of Qs, on them the wing armament was the two .5 gunpods instead of the four .3s inside wings on the earlier models. So I understand the sentence means that most of the planes were delivered to the units without any weight reductions.

I meant to ask does P-39 Expert has any proof for his belief that the .30s were deleted on the vast majority of Russian P-39s. And I did not count Qs because nobody could remove .30s from them because they had none. And yes, gunpods were removable.

Many P-39s were lost by Russians before the first Ns arrived and after that many older models were lost as were many Qs, even we (the Finns) got two in fairly good condition (they could have easily repaired to flying condition because we also recovered several wrecks), one is at our AF museum and the other was shown some time at our AA Museum.

Ps. I checked from my photos and noted that the P-39 shown at the AA Museum was the same White 26 that was shown at the AF Museum.

 

[P-39 Expert]

Hey man, I see where you're coming from but allow me to share.

I was born and raised on the family airfield, my dad and his brothers came back from WWII and turned the family farm in lower Michigan into a bona fide grass strip. We had two runways, four hangars, two of them quite large, repair shop with a mechanic and a pilots lounge. By the time I was 12 I probably spent more time in a Cessna than on my bicycle. (Although I haven't flown since 1978, but that's another story)

As a young lad I couldn't read enough about aerial combat from WWI - Korea, my book knowledge of ACM was essentially "attack from the sun, when bounced, turn into the attack, if in trouble dive away".

I haven't gone near a GA aircraft in decades, but what you can learn and discuss here makes me feel like I never left the GA world.

So when I found this place you can imagine how happy I was to find like minded (and VERY knowledgeable) fellows that are not only cordial, but go out of their way many times to help answer questions and share their years of experience and knowledge.

Why do I blather on like this? Because after YEARS of nothing but book learning, imagine again how exciting it was to learn that here I could actually talk to an F-15 pilot, I give BiffF15 (with two "ffs" + 1) a little razzing every now and then but it's all in good fun and he knows it. But when he discusses ACM I listen and when in doubt ask questions, some of them may be dumb but I don't let ego get in the way of learning.

Or drgondog my love of the P-51 is borderline fanatical, to get to ask questions and receive correct answers on a subject near and dear is simply outstanding, especially the minutiae he can come up with.

I have only illustrated two out of MANY here that you can learn from, I'd list them all but I don't want to leave anyone out and I think you already know who they are anyway.

I like you, you have proven you have knowledge and integrity, as I said before, it isn't easy to stay civil when your arguments are being refuted from all comers, but for the most part I believe you have kept the snark to a minimum and that speaks very highly of you. I doubt I could say the same for me in the same situation, just read my sig line...

In the end, I just wanted you to know that I think highly of what you know, just dial it back a bit and LISTEN to what these guys are saying, I'd NEVER question Wes ( X XBe02Drvr ) on what a critical engine may or may not be. He has age, wisdom and experience... well mostly age, which I respect.

I still think you are a valuable addition to the community here and can make valid contributions to our discussions, just my opinion but remember, my contribution here is just snark and dumb questions so take that for what it's worth.

Thanks.

 

[P-39 Expert]

I'm not a native English speaker, but the quote is: "The North Fleet Air Arm followed these recommendations and reduced the P-400's weight by 247 kg. Still, most aircraft were delivered unmodified." I read that that the North Fleet Air Arm removed wing guns but most other commands did not. IMHO all P-400s and P-39Ds - Ns arrived to the USSR with wing guns as did most of Qs, on them the wing armament was the two .5 gunpods instead of the four .3s inside wings on the earlier models. So I understand the sentence means that most of the planes were delivered to the units without any weight reductions.

Did the quote say what recommendations were used to reduce the weight by 247kg? That would be about 543lbs, right?

I meant to ask does P-39 Expert has any proof for his belief that the .30s were deleted on the vast majority of Russian P-39s. And I did not count Qs because nobody could remove .30s from them because they had none. And yes, gunpods were removable. I always understood they were delivered as manufactured with wing armament which was then removed by the Russians. Late model Q-20s were delivered without the wing guns.

Many P-39s were lost by Russians before the first Ns arrived and after that many older models were lost as were many Qs, even we (the Finns) got two in fairly good condition (they could have easily repaired to flying condition because we also recovered several wrecks), one is at our AF museum and the other was shown some time at our AA Museum.

Please expand above.

 

[P-39 Expert]

Hello P-39 Expert



Does this mean that you are sticking with your claim that the typical muzzle velocity of the 37 mm M4 cannon as installed in the P-39 was achieving 2600 - 3000 fps?



This sounds like you are accepting that the 37 mm cannon and .50 cal MG did not work well together.
Be careful. This is not in agreement with what you appear to be stating above.

Not at all. Worked just fine together out to 400yds. Past that they may need to be used separately.

The Airacobra also has a fairly large area in the wings occupied by fuel tanks that are no better protected.

Except by the main wing spar.

I have also read through a fair number of those reports from ww2aircraftperformance.
What they tend to indicate is that for specific examples, often the performance may be a touch higher than one might have expected. I am not discounting that information. I am just noting that the numbers from those test reports do not seem to be supported by actual combat reports. The other question to ask is whether the results of the test report are representative of the type or just of a particularly good example.
There are also test reports from the same time period that do seem to be much more in line with performance in the field.

Also, many of your CLAIMS of performance increases are based on ESTIMATES of the results of stripping off of "unnecessary" weight in equipment that the operators determined was necessary.

Estimates after removing unnecessary weight are only on the early D/F/K/L models with the -35 or -63 engines. N model didn't need any weight reduction at all, although it certainly would have benefitted from it. Q model certainly didn't need the .50cal wing gun pods. Just unnecessary drag that reduced speed by 14mph.

You also might want to note that many of the issues that have been brought up have been about handling problems, CoG issues, overheating problems and other issues which have not received mention in reports at ww2aircraftperformance. So far, your response to CoG issues seems to be to declare them to be incorrect. Interesting!

Right. Most P-39s caught fire from overheating on the ground. If they did manage to take off firing one shell from the nose cannon caused an immediate tumble from CG problems.

- Ivan.

Please expand above.

 

[fubar57]

Found this picture....

​

....in this book...

PUBLISHED BY ALASKA-SIBERIA RESEARCH CENTER - 2007
​

Its a P-63C-5-BE. Its the caption of the photo though, "Bell P-63 Kingcobra in flight over the Northwest Route with the inscription written in chalk on its fuselage reading "Bell Booby Trap" so named because the Bell planes, held up for mechanical repairs and delayed for extended periods of time in the outdoor cold, tended to be involved in a greater number of crashes than other aircraft. May 1945

 

[XBe02Drvr]

Your not supposed to shoot it (much) just carry it

I mostly just shoot my old style muzzle loaders now. More fun. Ever hear of "primitive biathlon"? Pre-1860 style muzzle loaders, traditional style snowshoes, and mountain trapper or period military costume if you're shooting in the "Classic" class. Davy Crockett/Daniel Boone or Native American style is OK too.

 

[glennasher]

I mostly just shoot my old style muzzle loaders now. More fun. Ever hear of "primitive biathlon"? Pre-1860 style muzzle loaders, traditional style snowshoes, and mountain trapper or period military costume if you're shooting in the "Classic" class. Davy Crockett/Daniel Boone or Native American style is OK too.

I drifted from "deer rifles" to varmint rifles, and now I'm kind of obsessed with rimfires of various natures, mostly well-crafted bolt-actions like CZ452s and 455s. Before I went nuts on rifles in general, I was a pretty good pistol shot, mostly USPSA/IPSC, with highly modified 1911 pistols, among others. I pretty much kept my rifles to .30/06 and under, though. I still keep a .270 around, along with some smallish varmint rifles, in case something needs killin'. Firearms are fun.

 

[Ivan1GFP]

Hello P-39 Expert,

Not at all. Worked just fine together out to 400yds. Past that they may need to be used separately.

You really don't understand deflection shooting or physics, do you?

Except by the main wing spar.

Are you trying to convince us that the rear wing spar offers significant protection from weapons fire?

Estimates after removing unnecessary weight are only on the early D/F/K/L models with the -35 or -63 engines. N model didn't need any weight reduction at all, although it certainly would have benefitted from it. Q model certainly didn't need the .50cal wing gun pods. Just unnecessary drag that reduced speed by 14mph.

Has anyone ever told you that trying to push a solution that the client clearly does not want is NOT a recipe for success?

Right. Most P-39s caught fire from overheating on the ground. If they did manage to take off firing one shell from the nose cannon caused an immediate tumble from CG problems.

I hadn't heard this before, but you must be right. The P-39 really must have been a piece of junk.

- Ivan.

 

[Ivan1GFP]

I mostly just shoot my old style muzzle loaders now. More fun. Ever hear of "primitive biathlon"? Pre-1860 style muzzle loaders, traditional style snowshoes, and mountain trapper or period military costume if you're shooting in the "Classic" class. Davy Crockett/Daniel Boone or Native American style is OK too.

Hello XBe02Drvr,

My own black powder shooting has never really been about Muzzle Loaders though I do own a couple.
The majority of my BP shooting has been with Sharps Rifles (reproductions) and I have run enough ammunition through a couple to put some pretty significant wear on the breech seals. Most of the other BP shooters were going through 3-10 rounds in an afternoon after work. I was going through 50-100 most of the time and sometimes a lot more.
These are the kinds of rifles that get pretty expensive to shoot if you don't cast your own bullets.

At one point I got pretty serious about seeing how accurate the M14/M21 platform could be made to be by using the appropriate Benchrest techniques on ammunition. Most folks shooting service rifle aren't really that interested in testing to see how accurate the system can be made. They are interested in competition in which a gun shooting 1 MOA is fantastic and 1.5 MOA is really quite sufficient to shoot a clean score.
I actually had a pretty good amount of success. The Benchrest shooters thought I was crazy to even try. A very good friend of mine tried to give me some ideas on how to improve my ammunition until I showed him how violent the cycling of the gun was and what it did to ammunition. After that, he shook his head and wondered how I was able to get any kind of accuracy much less the level of accuracy the targets were showing.

- Ivan.

 

[vikingBerserker]

I'm not a native English speaker, but the quote is: "The North Fleet Air Arm followed these recommendations and reduced the P-400's weight by 247 kg. Still, most aircraft were delivered unmodified." I read that that the North Fleet Air Arm removed wing guns but most other commands did not. IMHO all P-400s and P-39Ds - Ns arrived to the USSR with wing guns as did most of Qs, on them the wing armament was the two .5 gunpods instead of the four .3s inside wings on the earlier models. So I understand the sentence means that most of the planes were delivered to the units without any weight reductions.

I meant to ask does P-39 Expert has any proof for his belief that the .30s were deleted on the vast majority of Russian P-39s. And I did not count Qs because nobody could remove .30s from them because they had none. And yes, gunpods were removable.
.

Your English is perfectly fine, I believe Yefim's book was originally published is Russian so there might be a few things lost in translation. Based on your calcification then I have to agree with you, the only wholesale removal of the 0.30's from the wings I could find were those of the North Fleet Arm as mentioned.

 

[pinsog]

I drifted from "deer rifles" to varmint rifles, and now I'm kind of obsessed with rimfires of various natures, mostly well-crafted bolt-actions like CZ452s and 455s. Before I went nuts on rifles in general, I was a pretty good pistol shot, mostly USPSA/IPSC, with highly modified 1911 pistols, among others. I pretty much kept my rifles to .30/06 and under, though. I still keep a .270 around, along with some smallish varmint rifles, in case something needs killin'. Firearms are fun.

My 458 Lott and my sons 375 ultra mag are both on CZ550 Safari Magnum actions. Love the actions, the 458 holds 5+1. It actually holds 6 in the magazine but can't strip the top round off so I only load 5