SHOULD the P39 have been able to handle the Zero? Was it training or performance?

[parsifal]

RAF was very unhappy with the p-39s it received. it is not exaggerating to say they basically wanted to return them and get their money back. This is despite the generally favourable combat comparisons carried out at Duxford

One needs to remember the old axiom has it that the bombers deterimine the altitude at which fighters must fight. In the SWPA, the Japanese sent their bombers over generally at between 18,000 and 22,000 ft., sometimes substantially higher, seldom much lower. The air was generally very humid and heavy but with high levels of turbulence due to the frequent presence of large mountains. While the P-39 could get that high, it took it a long time to do so, so the and the opportunities for high altitude intercepts were few. Effectively, it was all done by about 17,000 ft. It was at its best below about 12,000 ft. Considering that the mountains in New Guinea rose to over 14,000 ft., and in the early days of the conflict both sides were going back and forth over those mountains to get at each other, the P-39 was at an instant disadvantage. Despite some rather fantastic claims by the USAAC units defending Port Morseby after March 1942, IJAAF losses to Cobra equipped units have been shown post war to be largely unsubstantiated.
.
The VVS was the other major user of the type. Soviets fought over terrain much like that of Iowa, were based close to the enemy, and the Germans chose to send their bombers over at medium and low altitudes. So none of the factors that worked against the P-39 in New Guinea were present on the Eastern Front.

Also worth noting. An RAF Duxford comparison test of a captured Me 109E and P-39C showed the Bell outperforming the 109 in every category except rate of climb when below 15,000 ft. The P-39 could easily out-turn the 109--it took the 'Cobra less than 720 degrees to get on the tail of an Me that was planted on its tail. So the P-39 should have had no trouble dealing with the 109 at the altitudes common in the East. But this assumes the 109 would accept a full turning fight, which was seldom the case. In the SWPA, however, the P-39 units again opted for manouvre fighting, but this time they were up against an aircraft that excelled at horizontal manouvre. Not only were the P-39s forced to fight at altitudes above where they were competitive, it had to contend with fighters that were much, much more maneuverable than it was. P-39 squadrons routinely stripped off the wing guns to get more performance, and some even ripped out the armor plating (which weighed about 750 pounds) to get yet more performance, preferring to reduce their susceptibility to battle damage (as the Japanese did) at the expense of vulnerability to it.

That said, the P-39 was not a complete failure in New Guinea. The two groups equipped with it--the 8th and 35th--performed quite effectively, but their victory claims are so dicey as to be not worth much consideration. . The two squadrons of the 8FG that relieved RAAF 75 Squadron at Port Moresby at the end of March, 1942, were the only fighter force available to stop the Japanese air onslaught. This they did, although at great cost.

 

[Shortround6]

I would note that by the time the P39 was coming into service (fall of 1941) the 109E was on the way out and the 109F was equiping more squadrons every month. WHile the 109F may not have turned any tighter than the 109E it could sustain height or speed in a turn much better than the 109E.

I also have doubts about pulling 750lbs of armor out of a P-39. according to the weight tables there wasn't over 275lbs to begin with. Not to mention that an empty P-39D-2/P-400 weighed about 5550-5600lbs, basic weight (empty equipped) with guns, armor, radio, and oxygen was 6330-6420lbs.

Now perhaps you could save 750lbs (or close to it) by taking out the four wing guns (and their ammo) the armor and about another 100-130 worth of stuff (no oxygen over the Owen Stanleys? No radio? leave out 20 gallons of gas?)
I have no doubt that the pilots and crews did strip stuff out of the planes, however the weight saved by stripping the armor seems to be abut as exaggerated as the some of the air to air victories.

 

[Peter Gunn]

Is this a wind up?

*SNIP*

My vote is an unequivocal "Yes".

 

[Hansie Bloeckmann]

The Breda 12.7 machine gun was just about as heavy as the US Browning.50. and was rated at 700rpm instead of 600. perhaps the fact that the bolt only had to move 79% as far due to the shorter ammo has something to do with the 16-17% higher rate of fire

I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns with an acceptable degree of reliability. That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high?





Other things in the nose of the P-39 include an oil tank for the reduction gear box, a glycol tank (not to be confused with the Prestone tank). the aircraft battery,
any oxygen tanks for the pilot. P-39s carried 200rpg for the .50 cal
I would note that 30 rounds of 37mm ammo weighs about the same as 200 rounds of .50 cal ammo. Yanking one 238lb gun and 60 lbs of ammo (298lbs) and replacing it with two guns weighing 138lbs and using 120lbs of ammo (258lbs) isn't really going to turn the P-39 into rocket plane.
Just use skinny pilots

This is only half jest. Early weight tables called for 160lb allowance for the pilot. later tables increased the weight to the more standard 200lbs although the 200lbs includes parachute. Not sure if the 160lb figure does.

Some units may have flown the P-39 with only 300rpg for the wing .30 cal but this saves about 165lbs.
30 rounds of 37 is less than 15 seconds firing time.
200 rounds of .50 cal is around 20 seconds assuming you can get the synchronized guns up to 600rpm.
300 rounds of .30 is about 15 seconds for the wing guns. 1000 rounds is ridiculous.
Under wing .50s had 300rpg and that is good for around 23 seconds at 780rpm.

 

[Hansie Bloeckmann]

The Breda 12.7 machine gun was just about as heavy as the US Browning.50. and was rated at 700rpm instead of 600. perhaps the fact that the bolt only had to move 79% as far due to the shorter ammo has something to do with the 16-17% higher rate of fire

I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns with an acceptable degree of reliability. That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high?





Other things in the nose of the P-39 include an oil tank for the reduction gear box, a glycol tank (not to be confused with the Prestone tank). the aircraft battery,
any oxygen tanks for the pilot. P-39s carried 200rpg for the .50 cal
I would note that 30 rounds of 37mm ammo weighs about the same as 200 rounds of .50 cal ammo. Yanking one 238lb gun and 60 lbs of ammo (298lbs) and replacing it with two guns weighing 138lbs and using 120lbs of ammo (258lbs) isn't really going to turn the P-39 into rocket plane.
Just use skinny pilots

This is only half jest. Early weight tables called for 160lb allowance for the pilot. later tables increased the weight to the more standard 200lbs although the 200lbs includes parachute. Not sure if the 160lb figure does.

Some units may have flown the P-39 with only 300rpg for the wing .30 cal but this saves about 165lbs.
30 rounds of 37 is less than 15 seconds firing time.
200 rounds of .50 cal is around 20 seconds assuming you can get the synchronized guns up to 600rpm.
300 rounds of .30 is about 15 seconds for the wing guns. 1000 rounds is ridiculous.
Under wing .50s had 300rpg and that is good for around 23 seconds at 780rpm.

I understood that the Germans took over the FN arms factories in Liegte, when they occupied Belgium in 1940--thus cutting off any ties with American gun companies (Colt) and designers (Browning)--I doubt the US standards for MG's, whether for aircraft, naval vessels or ground and armor troops were set too high--IMO anyway. Hansie

 

[Timppa]

Also worth noting. An RAF Duxford comparison test of a captured Me 109E and P-39C showed the Bell outperforming the 109 in every category except rate of climb when below 15,000 ft. The P-39 could easily out-turn the 109--it took the 'Cobra less than 720 degrees to get on the tail of an Me that was planted on its tail. So the P-39 should have had no trouble dealing with the 109 at the altitudes common in the East. ...ripped out the armor plating (which weighed about 750 pounds)

Also worth noting, P-39D was the first mass produced variant, about 650lb heavier than the -C. In the Eastern Front, about 1942 it (-D)was against the Bf109F rather than E, a completely better beast. 750 lb armour is not correct. It doesn't pass my BS meter even without checking.

 

[P-39 Expert]

Got a better idea for you. Compare 'Period P-39 vs Period 'whatever' at the rated Hp and Boost and combat weight for each?

The P-38C was in same period as the Bf 109F-1 and Spit Vb, delivered in January, 1941 with 20th completed in March 1941, None of the three P-39C's were close to meeting Bell claims for performance, nor were the production P-39D-1 and -2 delivered at the same time as the FW 190A-1. It was a hazard to life and limb without self sealing tanks and O2.

The P-39Q, introduced in Spring 1943 was first to achieve reliable 3200 fpm in Combat Power at S/L but reducing to ~ 3000 fm at 12000 and dropping to about 2000fpm at 20K. . Performance tests flown at design Combat load of 7570 #, but only included 87 gallons of fuel. With 33 gallon fuselage kit, the fuel load jumped to 120 gallons and 200 more pounds. It reached US combat zone with 332nd FG in February 1944 but were quickly swapped for P-40, then P-51B by June 1944.

So the P-39Q period to period has to compete with P-51B/C, P-38J-15, Spit XIV, FW 190A-7 and A-8, Bf 109G-6 - all of which climb faster at rated Combat Power (available with 150 grade fuel for example for the P-51B), are faster in level flight - at all altitudes- and roll with or better than the P-39Q. The Q would normally outturn all the above fighters except the Spitfire and the P-38J with boosted ailerons and skilled use of throttles. It has the shortest combat radius, is a sad sack above 20,000 feet and can't find a fighter to fight on even terms except for the occasional LW fighter flying low and medium fast where the P-39Q performs well... The ETO banished them to Bomb Squadrons in the 12th AF for close air support, the 9th/15th and 8th AF rejected them from operating in THEIR airspace, the SWP relegated them to CAS and then got rid of them as fast as P-40/P-38/P-47 and P-51s arrived.

See post #148 for the facts.

 

[buffnut453]

See post #148 for the facts.

Ok, this is really starting to look like a wind-up. Post #148 makes no mention of self-sealing fuel tanks or O2. You may well think that your pretty graphs make your point but they still miss the fundamental issue that the P-39C was NOT combat capable. The P-39D was the first truly combat-ready variant but it was a much heavier beast...with consequent loss of performance.

 

[Peter Gunn]

See post #163 for the facts.

Fixed that for ya.

 

[P-39 Expert]

Ok, this is really starting to look like a wind-up. Post #148 makes no mention of self-sealing fuel tanks or O2. You may well think that your pretty graphs make your point but they still miss the fundamental issue that the P-39C was NOT combat capable. The P-39D was a much heavier beast...with consequent loss of performance.

Pls explain "wind up"?

 

[buffnut453]

Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").

 

[P-39 Expert]

That might lead to a lot wrecked engines. I would double check your source on that.

The V-1710 went through 3 different crankshafts by Early 1942. The 3rd crankshaft stayed unchanged until the very late war 12 counterbalance cranks.
The first crankshafts were plain steel, by that I mean no special surface finish. the Next crankshaft was shot peened and had a much improved resistance to stress. It would operate practically forever at a level that would destroy the plain crankshaft in fairly short order. This was followed by a crankshaft that was both shot peened and nitrided. This crank would operate forever at stress levels that would destroy the shot peened crankshaft in short order.

Allowing full combat power for 15 minutes at a time was going to significantly shorten the life of the older crankshafts. The new crankshafts could be dropped into an old engine at overhaul time. Without some regard for the older engines this would be a very poor blanket policy. I don't know when the shot peened cranks were introduced but obviously the P-39C and the majority of the Ds and P-400s did not have the nitrided crankshafts.

You may also have a cooling problem, use of military power was always dependent on coolant and oil temperatures. If the temperature limit/s were exceed the engine had to be throttled back regardless of the number of minutes that been spent at that power level. If the P-39 was exhibiting marginal cooling in 5 minutes or under (although it can get pretty hot in Ohio in the summer) then pushing the engine for 15 minutes may not be a good idea.

I have no idea what, if anything, they did to address the cooling issues of the P-39C. One hopes they did something because if you are having cooling issues at 1150hp then with 1325hp engines or operating at WEP settings things are going into the red zone real quick.

You are truly an expert on crankshafts. My source for the 15 minutes is wwiiaircraftperformance.net. The actual government performance docs. Check them if you like.

 

[P-39 Expert]

Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").

Thanks, I had never heard that.

 

[Shortround6]

You are truly an expert on crankshafts. My source for the 15 minutes is wwiiaircraftperformance.net. The actual government performance docs. Check them if you like.

I have looked at some and have no desire to waste any more time, If you have a link to a specific document that says ALL V-1710 engines regardless of model or date of manufacture was cleared to use 15 minutes military power please post it.
I am not disputing that the standard was changed in the summer of 1942, Or that some V-1710 engines manufactured prior to that date were included in the order. But some is not all.

 

[P-39 Expert]

Ok, this is really starting to look like a wind-up. Post #148 makes no mention of self-sealing fuel tanks or O2. You may well think that your pretty graphs make your point but they still miss the fundamental issue that the P-39C was NOT combat capable. The P-39D was the first truly combat-ready variant but it was a much heavier beast...with consequent loss of performance.

#148 is talking about the P-39N, not the P-39C. The N was produced from December 1942 and was in action almost immediately. The FW190A6 was produced from June 1943 and was actually newer than the N. The P-39C was 7075#. It did not have self sealing tanks and armor plate/glass, but would have weighed the same because the self sealing tanks reduced fuel capacity by 50gallons or 300# and we were deleting the 2 .30caliber MGs in the nose so we could increase the 37mm cannon armament to the full 30 rounds. This was not the P-39C that was actually produced, just "what could have been". The P-39N/FW190A6 comparison was straight from the government performance tests.

 

[P-39 Expert]

The US use of the Aircrobra was also handicapped by climate. They usually try to adjust or correct performance figures to a "standard" day of 59 degrees F or 15 degrees C. and standard air pressure. Operating at temperatures much higher reduce performance due to less lift from the wing, less power form the engine (even at the same pressure) and less 'bite' from the propeller.
For some weird reason the US sometimes gave pilots charts that used a base line of 32 degrees F (0 degrees C) and the P-39 is one of those planes that use the point of freezing as a base line with notes to increase the take off distance and the time to hight by 10% for every 20 degrees F (or 10 degrees C) above the baseline. SO on a 92 Degree F day on a pacific Island or in North Africa the P-39 will need 30% longer runways and take 30% more time to make it to 15,000ft than the charts say. Other planes also suffered a similar loss of performance but if they started with a 59 degree base then they might only be around 15% below book figures. You can have hot days in Russia but a lot of their use would have been on days without such a large difference from the book figures.
P-39 had one of the higher wing loadings of the early fighters and one of the worst power loadings. (Not counting WEP) and may be affected even more by extreme heat.

Every other plane in that theater would have to adjust their performance figures too.

 

[pbehn]

Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").

Wind up, comes from the old clockwork toys, a person being wound up and set off in a particular direction for amusement like a toy. This is definitely a wind up, when you discuss removing armour, radios, fuel and guns to show how effective a plane could be the conversation borders on surreal.

 

[tomo pauk]

The problem there is that you're applying the retrospectroscope. In the mid-1930s, pretty much every fighter in the world was armed with 2 or 4 rifle-calbre machine guns. Even the early P-40s carried a mix of 30cal and 50cal weapons as late as 1941. I think it's asking a bit much for the crystal ball to foresee that 50cal weapons would be the preferable option in time to impact the Battle of Britain...and that's before we consider the other logistical issues.
...

Hurricane was not ordered with 2 or 4 RCMGs, but with 8. Ordering them with 4 HMGs instead does not rock the boat.
The CR.32 fighter, perhaps the last of the fighters with un-supercharged engines, was armed with two HMGs, with option for two 7.7mm MGs. French fighters, like the D.510, were armed with cannon + LMGs. Polish P.24 was armed with two cannons. COmpared with these 3 types, having 4 HMGs on a fighter with supercharged engine is nothing outrageous.
Both Italian and Belgian guns are in roduction much before ww2 started, ie. once can have them for Hurricane and Spitfire from the get go.

I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns with an acceptable degree of reliability. That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high?

Or perhaps Belgian technicians/gunners/engineers got to the solution earlier?
At any rate, one can buy earlier, 600-800 rpm models.

 

[buffnut453]

Hurricane was not ordered with 2 or 4 RCMGs, but with 8. Ordering them with 4 HMGs instead does not rock the boat.
The CR.32 fighter, perhaps the last of the fighters with un-supercharged engines, was armed with two HMGs, with option for two 7.7mm MGs. French fighters, like the D.510, were armed with cannon + LMGs. Polish P.24 was armed with two cannons. COmpared with these 3 types, having 4 HMGs on a fighter with supercharged engine is nothing outrageous.
Both Italian and Belgian guns are in roduction much before ww2 started, ie. once can have them for Hurricane and Spitfire from the get go.

Per my earlier post, the problem with US 50cals appears to have been belt-fed wing installations. The CR32 carried guns in the fuselage while the P.24 cannons were drum fed.

Having a workable HMG is one thing. Having an operationally viable belt-fed wing installation in the latest generation of 300+mph fighters is something else. If installing multiple HMGs in the wings of high-speed fighters was so straightforward, why did it take the US until late 1942 to get it right?

 

[Elmas]

Regia Aeronautica tried experimentally to install two MG in the wings of C.R. 32 but the wings did vibrate so much that shooting with some accuracy was impossible. This was the reason why the following Italian fighters, M.C. 200 and G. 50 had MGs in the fuselage.
Ing. Trojani, designer of A.U.T. 18, more or less contemporary of M.C. 200 and G. 50, had to insist with Gen. Cebrelli, Chief of Technical Services, to install MG in the wings of his aeroplane. But wings of C.R. 32 were maybe 12 cm thick, A.U.T. 18 were 37 cm at the Mg bays.
Chiefs of Technical services in the late 30s were still suspicious about the strenght of monoplane wings with D-boxes and stressed skin.