P-39 or P-40 for rest of war?

[michaelmaltby]

Glider my numbers may be flawed but I'm reading (P-39) 3,333 rate of climb vs; (Zero) 2,812 feet per minute

I think the fact that the Soviets re-wrote their tactics to stress the vertical (under 10 - 11, 000 feet) with the P-39 is an indication that at low altitude it was no "dog" "-)

"... 15 mins to get to 25,000 ft " --- 8 minutes to get to "fighting" altitude with my tacrics.

MM

 

[Markus]

I notice that a number of posts have said that the P39 was good in the climb. If the P39D took 15 mins to get to 25,000 ft and its my belief that the A6M2 made 20,000 in around 8 mins, then to put it briefly it sucked.

Is my understanding correct ie that the P39 was very poor in the climb or have I got it very wrong?

Depends. The P-39D´s climb rate was ~2,500 ft/min up to 12,000ft -the engine´s critical altitude -then the climb rate dropped to less than 1,000ft/min at 25,000ft. This translated into climb times of four, ten and fifteen minutes to 10, 20 and 25,000ft. The improved birds the Russians got could do it in three, seven and ten minutes but that´s not going to happen before 1943.

Several websites say the A6M had a climb rate of 3,100ft/min and since she had a two-speed supercharger the critical altitude of the engine is likely to be well above 15,000ft. One source says an early Zero reached 20,00ft in 7.5 minutes.

What bothers me is info that P-39 in Port Moresby ran for the sea when the Japanese attacked as they could not climb above them in time. (E. Bergerud: Fire in the Sky)

 

[Nikademus]

I notice that a number of posts have said that the P39 was good in the climb. If the P39D took 15 mins to get to 25,000 ft and its my belief that the A6M2 made 20,000 in around 8 mins, then to put it briefly it sucked.

Is my understanding correct ie that the P39 was very poor in the climb or have I got it very wrong?

I think it depended on the tactical situation. Dmitry Loza's "Attack of the Airacobra's" describes the development of high speed tactics that stressed Vertical maneuvers. The key points stressed were, "Altitude, speed, maneuver, fire" If the Cobra's kept their speed up and/or could dive down on their opponents they would be able convert it to quick altitude changes.

 

[Nikademus]

What bothers me is info that P-39 in Port Moresby ran for the sea when the Japanese attacked as they could not climb above them in time. (E. Bergerud: Fire in the Sky)

Believe part of that had to do with lack of early warning thx to the Owen Stanley mountains masking their approach. Zeros flew high cover and would tend to have alt advantage + the defenders would be at their most vulnerable while clawing for altitude. One difference i noted comparing Soviet and US experiences was that while the Airacobra would be comfortable in a turning fight against the Germans that would not be the case against Zeros, + Zeros can also quickly climb. If the Airacobra had a good burst of speed going and altitude was even, it would be in a much better position. Believe one or two A6M's were burned that way over Lunga. (Zeros down near ground level....P-400 comes blitzing in with all guns blazing at high level speed....boom)

A major change in tactics initiated within the 216th Fighter division while fighting the Kuban air campaign (mainly with Airacobra's along with a few Kittyhawks and Yak-1's) was dispensing with the old prescribed doctrine in regards to speed. It was too low, making the Soviet pilots patrolling more vulnerable. Higher speed was stressed along with pairs flying at different altitudes. The Soviet pilots would further increase their speed by trading altitude slowly. (essentially they adopted German Rotte and Scharm groupings)

 

[Shortround6]

Glider my numbers may be flawed but I'm reading (P-39) 3,333 rate of climb vs; (Zero) 2,812 feet per minute

I think the fact that the Soviets re-wrote their tactics to stress the vertical (under 10 - 11, 000 feet) with the P-39 is an indication that at low altitude it was no "dog" "-)

"... 15 mins to get to 25,000 ft " --- 8 minutes to get to "fighting" altitude with my tacrics.

MM

There are questions as to which P-39 you are comparing. 3 different engines. Early engine had 1150hp for take-off and low altitude with about 1125-1150 at 12,000ft. The next engine (in K&Ls) was good for 1325hp take off and still 1150 at 12,000ft but in WEP was good for 1590 at 2500ft. 3rd engine had 9.60 gears for the supercharger and traded low altitude power for height. 1200hp for take off and 1125 at 14,600ft WEP of 1420 at 9500ft. This engine was in the M, N, and Qs.
One book gives time to 25,000ft for a "D" model as 14.0 minutes while an "N" model could do it in 11.9min.
The real kicker beiing that it took the "D" 4.9 min to get from 20,000ft to 25,000ft while the "N" took 6.1 minutes to get from 15,000 to 25,000.
Russians also ditched the wing .50s and their ammo quite often.

 

[billswagger]

Im also thinking that the location of battle is likely to include war ships and a large part of the defense would be to have the capacity to ward off any navy to prevent invasion or bombings, and in that case you'd need a P-40. It had a combat radius of 400 miles with a bomb load, and 700 miles in a fighter configuration.

In that respect, i don't see the Japanese having the capability to fly high altitude missions where the P-40 couldn't also engage an attacking fleet.
The Japanese planes had the range but their ships would need to remain outside the range of the P-40s striking distance and this might actually mean a high altitude offensive from the Japanese was impossible. With the P-40 offering more maneuverability and adequate fire power to stop anything the Japanese could throw at them.

I think if the mainland were some how breached and the Japanese had captured an airbase and were able to operate from a portion of Australia then the P-39 may be more applicable. It would be needed to engage at higher altitudes and it had much better speed than the P-40, which is why the Russians spoke so highly of it. It was really the first plane that let them fight on somewhat more even terms with the Germans.
In this respect, the P-39 would be more suitable to stop multiengined bombers flying at higher altitudes and fast enough to avoid having to engage with enemy escorts.
Other than that, the P-39s superior speed is not that much of an advantage over the P-40 because the Zero was slower than both, and what the P-39 made up for in climb lacked in turning ability. Its my belief that an army could not rely on the P-39 alone against the Japanese, but i couldn't say the same for the P-40, So, im thinking the P-40 is gonna be the better bird for this battle.




Bill

 

[Colin1]

In this respect, the P-39 would be more suitable to stop multi-engined bombers flying at higher altitudes and fast enough to avoid having to engage with enemy escorts

Other than that, the P-39s superior speed is not that much of an advantage over the P-40 because the Zero was slower than both,

and what the P-39 made up for in climb lacked in turning ability

What advantage would the P-39 offer the Australians over the P-40 for higher-altitude work?

I don't recall the A6M being decisively slower than the P-40 at any stage up to late 1943/early 1944, when the A6M had other US fighters to worry about anyway.

The P-39 was not lacking in turning ability, unless you're comparing it with the Japanese fighters where most Allied fighters fell short.

 

[Glider]

Can I thank everyone for their replies to my question. The consensus seems to be that the P39 had a speed advantage over the Japanese at all altitudes and could dive away from trouble. Its turn was good but not up to Japanese standards and its climb was average at lower altitudes and dire over 15,000.

For the P39 to have a chance depends on the Japanese attacking at low altitude and not twigging on to the problems the P39 had at altitude. If the Zero's are escorting bombers at say 20 - 25,000 ft then the P39 would be fighting for altitude with the Zero's diving on them. The only choice for the P39 would be to dive away and they would find it difficult to impossible to regain any height without getting shot to bits.

The various ft/min figures are interesting but often forgotten is that in a combat situation the angle of climb is at least as important as the rate of climb. The Zero clmbed at a very steep angle and few if any fighters at the start ofthe war could stay with them and if you cannot match the climb then you may well not be able to get your guns on target. Even if the P39D could climb at 3,000 ft/min then it can only do that for seconds or it wouldn't take 15mins to get to 25,000ft which averages out at about 1,600ft min.

 

[michaelmaltby]

"... and not twigging on to the problems the P39 had at altitude". You know that's impossible. They captured Allison-powered US fighters.

MM

 

[renrich]

Billswagger, don't know where you get the combat raius of the P40 but you are not even close. A landbased A6M barely had a combat radius of 500 miles. The P40 would be doing good to have a 175 mile CR.

 

[Jabberwocky]

Billswagger, don't know where you get the combat raius of the P40 but you are not even close. A landbased A6M barely had a combat radius of 500 miles. The P40 would be doing good to have a 175 mile CR.

Truth is somewhere in between actually:

Going off the RAAF P-40 data sheets:

Range (NOT radius):
Internal fuel:

P-40E: 675 miles
P-40F: 815 m
P-40K: 670 m
P-40M: 695 m
P-40N: 550 m

With External fuel:

P-40E: 1,110 miles
P-40F: 1,085 m
P-40K: 975 m
P-40M: 985 m
P-40N: 875 m

Typically, combat radius is ~35% of absolute range, so best radius for the P-40 would be about 390 miles for the P-40E with full internal and external tanks, for a P-40E. Worst is just 305 miles for the P-40N.

With just internal fuel, best combat radius is about 285 miles for P-40F (Merlin was slightly less thirsty than the Allison at cruise, only by about 5-10% though, depending on altitude). Worst is just 190 miles, again for the N.

Personally, I'd rather the P-40 than the P-39. While its performance is not quite as good, the aircraft can be more easily adapted for the Merlin, so you always have the potential of sticking a two speed, two stage Merlin in later in the war. Later war P-40L/P-40Ns were already pushing 360-370 mph with Merlins or higher alt rated Allisons, like the -81/-83.

You could go for a two aircraft solution: Longer ranged Merlin powered P-40s for high alt work (+16,000 ft), short ranged Allison powered versions with more power down low for low alt work and fighter bombing.

Range is better than the P-39's (by about 20-30% usually). This is important in Australia and later in the PAcific, where fighters will have to cover a lot of ground.

The P-40's ruggedness also lends itself to ground attack better. Ultimate bomb-load for the P-40 was 1,500 lbs, including 2 x 250 lbrs on each wing.

Its also less of a maintenance hog, and its easier to service.

Armament APPEARS heavier on the P-39, but the 37 mm was very unreliable and more a detriment than an asset. The P-40s 4/6 .50 armament is fine to deal with any likely opponent, with the possible exception of the heavy flying boats.

 

[Glider]

"... and not twigging on to the problems the P39 had at altitude". You know that's impossible. They captured Allison-powered US fighters.

MM

I know

 

[Shortround6]

Personally, I'd rather the P-40 than the P-39. While its performance is not quite as good, the aircraft can be more easily adapted for the Merlin, so you always have the potential of sticking a two speed, two stage Merlin in later in the war. Later war P-40L/P-40Ns were already pushing 360-370 mph with Merlins or higher alt rated Allisons, like the -81/-83.

You could go for a two aircraft solution: Longer ranged Merlin powered P-40s for high alt work (+16,000 ft), short ranged Allison powered versions with more power down low for low alt work and fighter bombing.

I have my doubts about a two stage Merlin in a P-40, the engine may fit but you ave to stick the intercooler radiator somewhere.

P-40Es and Fs could already hit 360mph.

 

[tomo pauk]

The 'in-between' solution to improve P-40 performance would've been installation of Merlin 40 series With 1400-1500 HP that seems the most expedient, and was very much feasible as early as mid 1941 (so the Aussies can get that at least in mid 1942 in their P-40s).

The single-stage Merlin 40s were perhaps possible for P-39, but P-40 would've take it without too much rework.

 

[billswagger]

What advantage would the P-39 offer the Australians over the P-40 for higher-altitude work?

I don't recall the A6M being decisively slower than the P-40 at any stage up to late 1943/early 1944, when the A6M had other US fighters to worry about anyway.

The P-39 was not lacking in turning ability, unless you're comparing it with the Japanese fighters where most Allied fighters fell short.

The A6m was as much as 30mph to 50mph slower than the P-40 depending on altitude and variant.

The P-39 was reported in Russian interviews to be significantly faster at 6000m than the P-40, It was also better in the vertical for this reason, however the Russians also maintained that the P-40 was better in the horizontal and a dogfight in the P-39 was to be avoided. I can only assume this means the P-39 was not particularly good at turn fighting,

It also looks like i misinterpreted the ranges for the planes but the ideology is the same.


Bill

 

[MikeGazdik]

I think another important consideration is the willingness of the supplier (U.S. Army Air Corps) to provide needed aircraft. History shows they gave up on the P-39 early, whereas they kept the P-40 for issue to thier own air forces.

I think this would lead us again to the P-39 being released for export / Lend-Lease much sooner than the P-40. At least in much greater numbers.

 

[Timppa]

The responsibility of the squadrons under your command will just be defense of your country, not advancing against Japan. Which type would you pick?

P40, especially the P-40F (Merlin) submodel. Reasons:
- P-40F has significantly more range than any P-39 submodel.
- P-40F has slightly better high altitude performance.
- P-40 is much less prone to stall/spin, which is important in high altitude combat. Also it makes is less accident prone. Any commander hates losing pilots without enemy firing a shot.
- P-40 armament of six reliable .50's is very adequate against any Japanese aircraft. The 37mm cannon of the P-39 had some jamming problems, also it is a short range weapon due to low muzzle velocity.

 

[davebender]

Formosa to Manila is about 550 miles. Historical evidence suggests A6M2s of the IJN 11th Air Fleet managed that trip several times with enough fuel remaining to engage the American defenders in combat.

 

[bobbysocks]

how many P 40s/P39s were in still used in combat by 1944? a wealth of the US 40s were used for advanced fighter/gunnery training in GA or FL.

 

[Vincenzo]

The A6m was as much as 30mph to 50mph slower than the P-40 depending on altitude and variant.

Bill

maybe but over 6000 meters Zero were fastest, and also at P-40 FTH 50 mph slower afaik it's too for contemporary P-40 and Zero