XP-39 II - The Groundhog Day Thread

[Elmas]

Don't disagree. However, during WW2 it's usually the Brits who get painted as the rule-bound bureaucrats while the American free-spirit-thinkers just did what was needed to get the job done. Given the very rough field conditions at Guadalcanal, I have a really hard time believing that stuff-shirtedness would last very long.

Maintenance rules were being broken all the time on Guadalcanal as wrecks were cannibalized for spares. The prospect of greatly improving the performance of the key USAAF fighter in the region by "simply" removing some unnecessary armour plate and the "useless" wing guns strikes me as small beans compared to some of the hybrid airframes that are seen in photos. The book "Lightning Strikes" by Donald A. Davis describes one of the hybrid airframes at Cactus:

"Since there were so few P-400's in service, every cannibalized part could keep another plane flying. The favorite P-400 on the island was a battered craft that had skidded to a halt one day after landing on its belly because its wheels collapsed. It came to a rest with a wing crumpled and the propeller bent, making it an open source for spare parts. However, the need for flyable aircraft was so great that mechanics nursed it back to health. One wing was U.S. Army olive green and the other was British camouflage. Instruments were plugged into gapping holes in the cockpit panel. The three-bladed propeller contained two blades from one wrecked plane and one blade form another; it was balanced by pouring lead in until it spun almost correctly. The aircraft took on a strange personality all its own and would outlast every other plane in the squadron. It was proudly christened The Resurrection."

Given that mish-mash of parts and missing components, the prospect of taking out armour plate and a couple of wing guns really is trivial.

It wasn't done just in Guadalcanal...

 

[Ivan1GFP]

The P-39D-1 was the heaviest of the early P-39s at 7850lbs. My whole point is that the weight could be easily reduced AT FORWARD BASES by removing some equipment that wasn't needed. The weight reduction was primarily to increase climb rate and ceiling AT ALL ALTITUDES. The P-39 was already 40mph faster at all altitudes than the 1942 Zero. Just using combat power in climb would make the early P-39s equal to the Zero, and the weight reduction would increase climb rate to well above the Zero. With climb AND speed greater than the Zero the air battles would have been very different.

Hello P-39 Expert,

Despite evidence to the contrary, you refuse to accept that the early P-39 really DIDN'T have a 40 MPH speed advantage over the A6M2. The problem also is that very often actual maximum speed is meaningless because of how long it takes to get there. The A6M in most models had extremely good low and medium speed acceleration which is why the tests against the Aleutian A6M2 didn't start there. If the P-39 takes the time to fly straight and level to accelerate to the point where it can pull away from the A6M2, it has spent far too long in gun range.

The testing described in IIS 85 showed that even at the P-39D's dritical altitude at which its engine has the greatest advantage, the A6M2 had gained the advantage in climb rate. Power would fall off pretty quickly after that.
The A6M2 only had a critical altitude about 1000-1500 feet high but for some reason was able to maintain its climb rate much better.

Now keep in mind that even though the A6M2 had better climb performance, the Japanese themselves recognized that it was at a disadvantage in combat at higher altitudes which is why later models of A6M switched to a two-speed supercharger.

The extra weight and the 110gal drop tank meant the P-39 had trouble getting over 17-18000'. Too bad for the guys that were there, made their lives very difficult.

The problem is that without the drop tank, the P-39 didn't have the endurance to do anything useful or even get to where the fight was.

Regarding the FW190A, look at the climb charts for each model -3 through -8. They are all about the same. Much lower than Faber's 190A-3 as tested by the British.

That is probably because the typical testing of climb performance was at 1.35 ATA and 2450 RPM while Faber's A-3 was tested at 1.42 ATA and probably 2700 RPM.
By the way, which chart shows tests of the Ground Attack version I was referring to?
If your charts show nearly the same climb performance for the FW 190A-3 through FW 190A-8, there is something seriously wrong. The late models weighed over 1200 pounds more than the early ones and were not nearly as slick because of changes in armament.

- Ivan.

 

[P-39 Expert]

So you do what every good to tinkerer does and try an experiment. That's what the Aussies did. They took one Buffalo, stripped out the excess weight, replaced the wing 50 cals with 30 cals, replaced the 50 cal fairing bumps with smooth sheet, and then they flew a trial against a standard Buffalo. The results were good enough that, reportedly, they made the change to all the squadron's aircraft (although none of the other Buffalo squadron's followed suit).

None of the above was challenging and it gave a good enough demonstration of the performance improvement. You still need to find a worthwhile excuse for why at least one USAAF P-39/400 squadron didn't attempt something similar.

As to the armour for the engine, I never said there wasn't any. I said Wagner asked for more of it.

So substituting two .30calMGs for two .50calMGs saved, what, 100lbs? And that improved performance enough to modify the whole squadron? And removing 300+lbs wouldn't help a P-39? I have no excuse for why the weight wasn't reduced on P-39s. But I am sure it would have helped tremendously.

 

[buffnut453]

So substituting two .30calMGs for two .50calMGs saved, what, 100lbs? And that improved performance enough to modify the whole squadron? And removing 300+lbs wouldn't help a P-39? I have no excuse for why the weight wasn't reduced on P-39s. But I am sure it would have helped tremendously.

Sorry, but you have to explain why it wasn't done and why Wagner was asking for more armour not less. Frankly, I trust the experience of the operators at the time. If the improvements you cite would have improved performance to the extent you propose, I have to believe it would have been attempted.

The other option is that the theoretical benefits you keep pushing based on performance diagrams weren't achievable in the real world, and the men who were there at the time knew they were already wringing out the maximum performance from their aircraft.

My company prides itself on solving hard problems in the public interest. Typically, if there's an easy solution to a hard problem, then we don't get involved because it's already been tried. I think that principle applies in the case of the P-39. If it could have been substantively improved in the field, it would have been. I'm afraid no amount of theoretical chart analysis will change that.

 

[Ivan1GFP]

While I'm on a roll here, also remember a few weeks ago the discussion of how Americans were so much better equipped for WW2 because they all had Model Ts and knew how to tinker with engines? Now, apparently, it was beyond the ken of those same Americans to realise that removing unnecessary weight from an aircraft would improve its performance...and that they couldn't work out how to demonstrate those benefits objectively.

C'mon fellas...pick one side of an argument and stick with it, please.

Hello buffnut453,

I would say there is a vast difference between messing with a car in which screwing up just means you pull it over on the side of the road and finding out you screwed up in an aeroplane while flying at 10,000 feet.

I once watched a family living next to me spend over a month pulling out an old V-6 from a sputtering and battered old Buick Regal and order a Chevy 350 crate motor to replace it. They eventually got it installed. It sounded pretty good and could chirp the tires nicely.
A couple weeks later, the car disappeared. They didn't seem to want to talk about what happened so I didn't ask.

I remember watching as my Dad tried to explain to their dad why their lawn mower would not start. From that conversation, I gathered that the general level of technical knowledge and analytical ability in that bunch wasn't really that high but it never stopped them from working on their own cars.
A lot of people may work on cars, but that doesn't mean everyone is good at it.

- Ivan.

 

[P-39 Expert]

Sorry, but you have to explain why it wasn't done and why Wagner was asking for more armour not less. Frankly, I trust the experience of the operators at the time. If the improvements you cite would have improved performance to the extent you propose, I have to believe it would have been attempted.

The other option is that the theoretical benefits you keep pushing based on performance diagrams weren't achievable in the real world, and the men who were there at the time knew they were already wringing out the maximum performance from their aircraft.

My company prides itself on solving hard problems in the public interest. Typically, if there's an easy solution to a hard problem, then we don't get involved because it's already been tried. I think that principle applies in the case of the P-39. If it could have been substantively improved in the field, it would have been. I'm afraid no amount of theoretical chart analysis will change that.

In May of 1942 Larry Bell sent the AAF a list of weight reduction items that would have saved 1000lbs. None were implemented by the AAF.

 

[buffnut453]

In May of 1942 Larry Bell sent the AAF a list of weight reduction items that would have saved 1000lbs. None were implemented by the AAF.

Again, stick to one side of the argument please. This observation is at the AAF level yet previously you said that all the changes you propose could have been done by squadrons in the field. AAF policy had little meaning at Guadalcanal.

You cited Wagner's combat record as evidence of the P-39s qualities and yet that same Wagner wanted more armour protection AND he wanted the 30 cals in the wings. He never said "stop putting useless 40 cals in the wings", he just wanted the guns to work.

You're the one who keeps adding the adjective "useless" to the wing 30 cals and yet Wagner still wanted them. If he didn't, he'd have said so. Therefore, the operational squadron boss didn't find them useless.

You really have to come up with some explanation for why your "simple" changes weren't implemented. The actual reason, I suspect, is that the operational pilots wanted every item that they flew with, and none of it was "useless" from their perspective.

 

[buffnut453]

Hello buffnut453,

I would say there is a vast difference between messing with a car in which screwing up just means you pull it over on the side of the road and finding out you screwed up in an aeroplane while flying at 10,000 feet.

I once watched a family living next to me spend over a month pulling out an old V-6 from a sputtering and battered old Buick Regal and order a Chevy 350 crate motor to replace it. They eventually got it installed. It sounded pretty good and could chirp the tires nicely.
A couple weeks later, the car disappeared. They didn't seem to want to talk about what happened so I didn't ask.

I remember watching as my Dad tried to explain to their dad why their lawn mower would not start. From that conversation, I gathered that the general level of technical knowledge and analytical ability in that bunch wasn't really that high but it never stopped them from working on their own cars.
A lot of people may work on cars, but that doesn't mean everyone is good at it.

- Ivan.

Ivan,

I wasn't the one pushing that idea, in fact I find it vaguely ridiculous. Other forum members were suggesting that American youth grew up with an inmate ability to resolve mechanical problems because every farmer had a beat-up Model T. It's an attempt to demonstrate American exceptionalism compared to other nations in an area where, frankly, it didn't exist.

 

[XBe02Drvr]

Oh come off it. Are you really suggesting that it's the Brits fault that Americans didn't take steps to improve their own aircraft? Really??? That's too much. Has ANY American listened to a Brit since 1775?

No, I'm suggesting the cultural climate of the USAAF's hosts might have had an inhibiting effect on the more innovative impulses of the American squadrons. Not blaming the British, just acknowledging their potential influence. The farther they get from HQ and the big brass, the less inhibited the innovators become.

 

[buffnut453]

No, I'm suggesting the cultural climate of the USAAF's hosts might have had an inhibiting effect on the more innovative impulses of the American squadrons. Not blaming the British, just acknowledging their potential influence. The farther they get from HQ and the big brass, the less inhibited the innovators become.

I still don't buy it. US-Brit relations may have been relevant at the operational level but not at the squadron level.

 

[XBe02Drvr]

Hello XBe02Drvr,

You might be right, but I suspect that more likely it was the one that ended up stuck in the mud for a couple months when the plane flipped over. That blade sticks out pretty far and the flip was violent enough to destroy the canopy and buckle the fuselage at the cockpit. I still can't quite figure out how exactly the plane wiped off both main gear, scraped up the belly and flipped without that much damage to the underside of the cowl or the other two prop blades.

- Ivan.

Visualize Koga's approach. He's touching down in tall grass with an unknown surface below. Because of his flat viewing angle, he's not going to catch the gleam of the water below. The slowest, softest touchdown with a taildragger is accomplished with an exaggerated three point landing, likely tailwheel first, and the engine ticking over a little above idle to aid in controllability. This was a one shot attempt, as his engine was practically out of oil and not likely to survive a go around.
As his tailwheel starts to drag in the tundra, the mains splash down, dig in hard, and flip the plane violently ass over teakettle onto its prop spinner then onto its back, capturing one prop blade underneath and sudden-stopping the engine. The main gear struts probably didn't come completely unglued until after the somersault impetus was well underway. I remember reading that one of the recovery party remarked that the landing gear struts were lying in rather odd locations, given the imagined gyrations of the aircraft.
Take a model of a Zero or other low wing taildragger and "hand fly" it through a couple table top three point landings, noting the angles at which the landing gears contact the surface. I think it will become self evident.

 

[XBe02Drvr]

One logical conclusion is that they didn't think it would help much.

Valid point, and I think, a likely answer. I tend to think that in extreme situations the guys on the flight line tend towards doing what needs to be done, while the chain of command is apt to lean on "by the book". The more remote the flight line is from the chain of command, the more likely are experimentation and innovation to flourish.

 

[Shortround6]

So substituting two .30calMGs for two .50calMGs saved, what, 100lbs? And that improved performance enough to modify the whole squadron? And removing 300+lbs wouldn't help a P-39? I have no excuse for why the weight wasn't reduced on P-39s. But I am sure it would have helped tremendously.

Changing the .50s for .30s would save only about 100lbs, you are correct on that. but guns without ammo are pretty worthless. You can carry 500 rounds of .303 for the same weight as 100 rounds of .50 cal ammo. I don't know what that squadron was using for an ammo load for the .50s per gun nor do I know what they used for the .303s but obviously there is another 60-100lbs of weight loss just in ammo. I don't know if they took anything else out.

Then we have the 37mm problem, it wasn't very reliable at first, yes it got fixed, but when? Taking out the .30s in early/mid 1942 if the 37mm wasn't fixed yet might not have been a good idea? Apparently many of the US gun installations were not trouble free in early 1942.

the 'worthless' wing 30s were about 3 times the firepower of the cowl guns in the A6M2. Perhaps the Japanese should have pulled those guns to improve performance?

 

[XBe02Drvr]

apparently, it was beyond the ken of those same Americans to realise that removing unnecessary weight from an aircraft would improve its performance...and that they couldn't work out how to demonstrate those benefits objectively.

C'mon fellas...pick one side of an argument and stick with it, please.

Colonel REMF: "Lieutenant, what are you doing to that aircraft? Who authorized it?"
Lieutenant Nonothing: "Sir, my crew chief and I are conducting an experiment, Sir. Removing useless weight to improve performance, Sir! Our squadron maintenance officer said he thought these planes are overweight and causing our heavy losses in combat, Sir."
Colonel: "Lieutenant, every item in that aircraft is ESSENTIAL! Otherwise the Air Corps wouldn't have put it there! Now put all that stuff back in where it belongs, and don't make any changes unless IAW the P39 Maintenance Tech Order, DO YOU READ ME, LIEUTENANT?"
Lieutenant: "Yes Sir!"

A bit exaggerated, but indicative of an attitude that might explain the lack of initiative in "fixing" the P39.

 

[buffnut453]

Colonel REMF: "Lieutenant, what are you doing to that aircraft? Who authorized it?"
Lieutenant Nonothing: "Sir, my crew chief and I are conducting an experiment, Sir. Removing useless weight to improve performance, Sir! Our squadron maintenance officer said he thought these planes are overweight and causing our heavy losses in combat, Sir."
Colonel: "Lieutenant, every item in that aircraft is ESSENTIAL! Otherwise the Air Corps wouldn't have put it there! Now put all that stuff back in where it belongs, and don't make any changes unless IAW the P39 Maintenance Tech Order, DO YOU READ ME, LIEUTENANT?"
Lieutenant: "Yes Sir!"

A bit exaggerated, but indicative of an attitude that might explain the lack of initiative in "fixing" the P39.

Believe me, I'm fully conversant in the ways military intransigence can rear it's ugly head. However, I'm pretty certain there weren't many REMF O-6s in either PNG or Guadalcanal.

Also, I'm going to stress (again) Wagner's critique of the P-39. He wanted more armour to protect the engine and wing 30 cals that worked. Therefore, he clearly didn't think there was excess "useless" weight to be removed. Also he was an O-5 in charge of a squadron...and I don't see him listening to any O-6 REMF (i.e. "It's my squadron and I'll do what I want with it. You aren't in my chop chain, sir, so you can go and do u speakable things to yourself...with all due respect, sir.").

 

[Milosh]

I am not sure of the exact fuel used at the time. My point was that there was no British fuel the same as there was no US fuel it was as far as possible a universal Allied fuel.

There might have been a standard spec but part of the problem with the P-38 at one time, iirc, was the use of 'Brit' avgas. When American avgas was used the problem disappeared. Anyways, the fuel used in Faber's 190 was drawn from a 'Brit' fuel tank.

 

[buffnut453]

Changing the .50s for .30s would save only about 100lbs, you are correct on that. but guns without ammo are pretty worthless. You can carry 500 rounds of .303 for the same weight as 100 rounds of .50 cal ammo. I don't know what that squadron was using for an ammo load for the .50s per gun nor do I know what they used for the .303s but obviously there is another 60-100lbs of weight loss just in ammo. I don't know if they took anything else out.

In addition to swapping out the wing guns, the Aussies also reduced ammo load, removed the radio mast, the signal flare system (this was not a hand-held Very pistol but, rather, a substantial metal tube located in the rear fuselage), cockpit heater and ducting, and a few other items I can't recall off the top of my head.

I didn't want to specify everything previoualy because the exact details aren't germane to the general question of why USAAF squadron's didn't attempt something similar.

 

[P-39 Expert]

Changing the .50s for .30s would save only about 100lbs, you are correct on that. but guns without ammo are pretty worthless. You can carry 500 rounds of .303 for the same weight as 100 rounds of .50 cal ammo. I don't know what that squadron was using for an ammo load for the .50s per gun nor do I know what they used for the .303s but obviously there is another 60-100lbs of weight loss just in ammo. I don't know if they took anything else out.

Then we have the 37mm problem, it wasn't very reliable at first, yes it got fixed, but when? Taking out the .30s in early/mid 1942 if the 37mm wasn't fixed yet might not have been a good idea? Apparently many of the US gun installations were not trouble free in early 1942.

the 'worthless' wing 30s were about 3 times the firepower of the cowl guns in the A6M2. Perhaps the Japanese should have pulled those guns to improve performance?

Four .30calMGs with two synchronized is not much armament for a modern fighter.

I was assuming the ammo load weight for both the .30s and .50s was approximately the same.

 

[P-39 Expert]

Colonel REMF: "Lieutenant, what are you doing to that aircraft? Who authorized it?"
Lieutenant Nonothing: "Sir, my crew chief and I are conducting an experiment, Sir. Removing useless weight to improve performance, Sir! Our squadron maintenance officer said he thought these planes are overweight and causing our heavy losses in combat, Sir."
Colonel: "Lieutenant, every item in that aircraft is ESSENTIAL! Otherwise the Air Corps wouldn't have put it there! Now put all that stuff back in where it belongs, and don't make any changes unless IAW the P39 Maintenance Tech Order, DO YOU READ ME, LIEUTENANT?"
Lieutenant: "Yes Sir!"

A bit exaggerated, but indicative of an attitude that might explain the lack of initiative in "fixing" the P39.

Agree, especially at this very early stage in the war for the AAF.

 

[P-39 Expert]

Again, stick to one side of the argument please. This observation is at the AAF level yet previously you said that all the changes you propose could have been done by squadrons in the field. AAF policy had little meaning at Guadalcanal.

You cited Wagner's combat record as evidence of the P-39s qualities and yet that same Wagner wanted more armour protection AND he wanted the 30 cals in the wings. He never said "stop putting useless 40 cals in the wings", he just wanted the guns to work.

You're the one who keeps adding the adjective "useless" to the wing 30 cals and yet Wagner still wanted them. If he didn't, he'd have said so. Therefore, the operational squadron boss didn't find them useless.

You really have to come up with some explanation for why your "simple" changes weren't implemented. The actual reason, I suspect, is that the operational pilots wanted every item that they flew with, and none of it was "useless" from their perspective.

I have only one side of any P-39 argument: the early D/F/K/L models with the 8.8 supercharged engines were way overweight at 7650-7850lbs. Removing some useless or redundant equipment would have improved their climb rate/ceiling substantially and allowed them to dominate the early A6M2 Zero. Speed advantage+climb advantage+dive advantage.

And Wagner's assessment was after only the first week of combat. If the P-39s were lighter and could get above the Zeros he wouldn't have needed any extra engine armor.