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

[Jerry W. Loper]

You're the officer in command of a small country's fighter defense squadrons. Let's say the country is Australia and the date is December 1941 or January 1942. The crazy Japanese just bombed Pearl Harbor and are running rampant in the Pacific. For the rest of the war, your squadrons will be provided an adequate supply of American single-seat fighters. The catch is, they'll be either P-39s or P-40s (all the different models of each main type will become available). The responsibility of the squadrons under your command will just be defense of your country, not advancing against Japan. Which type would you pick?

 

[Colin1]

If the constraints are

single-stage Allison technology
interception only

then it's got to be the P-39. It was faster than any version of the P-40 and was more powerfully armed.

Range will still be an issue, even for interception, Australia is rather large.

 

[timshatz]

Colin has hit the nail on the head with the problem both aircraft give you. Range. Neither has anything worth talking about. Not even sure which is better but I would guess it would be slightly better in the P40. But, that besides, I would go with the P40. It was still in service with the Allied Forces (USAAF, RAAF and RNAF) long after the P39 was relagated to second line allies (France, Italy, ect.) and the Soviets. There had to be a reason for that.

Either way, it's gonna be a rough war for Australia if all they have is the P40 or P39

 

[Nikademus]

The Russians preferred the P-39 over the P-40 and used it right up to the end of the war.

 

[michaelmaltby]

Assuming that Japanese bombers are not attacking from high altitude, I would select the P-39. The key would be emulating the Soviets -- strip off the wing guns to save weight and operate with just the nose cannon and machine guns. Get close.

MM

 

[Glider]

P40 all the way. The P39 had nasty spin habits its favourite being a flat spin and had significant COG problems. Such were these that in theory it was dangerous to fire the nose gun ammunition in that the plane shouldn't be flown without it in place.
In addition the P40 was a decent fighter at lower altitudes and was way ahead of the P39 in GA. Taking the wing guns off the P39 would leave it poorly armed, as the 37mm was at best marginal for air to air combat with a low mv and slow ROF.

Photo attached re the ammo, apologies to those who have seen it before

 

[Thorlifter]

As much as it hurts to say, I'd have to go with the P-39. A bit less range, but faster, better armed, much better rate of climb. And who knows, if it was the front line fighter for Australia, it may have prompted a little better engine, especially if altitude was an issue with getting to the attacking bombers.

But that's only if one of it's primary roles was bomber defense. If we are talking about using it primarily as a air superiority or a dog fighter, it's absolutely the P-40.

 

[michaelmaltby]

Thorlifter - agreed

MM

 

[Colin1]

But that's only if one of it's primary roles was bomber defense. If we are talking about using it primarily as a air superiority or a dog fighter, it's absolutely the P-40.

The P-39 could climb all over the Bf109E
If the Aussies did go ahead and do some work on the engine, who's to say it couldn't have climbed all over the Bf109F?

 

[tomo pauk]

If we are allowed to use only the real planes, P-39 would've been my choice.

If we are allowed to modify (in a realistic way) either design, I'd go with P-40.
The engine position allows for non-problematic engine change (Merlin 60 series would've been no-brainer, but we can consider Bristol Hercules, R-2600, R-2800 etc), it would have been easily lightened, version with just 4 x 0.50in would've had enough fire power for fighter's job, it was regarded as a sturdy plane, and the combat range was decent.

 

[michaelmaltby]

A cannon is essential - the 37 mm Olds was problematic - but for close in work (as the Soviets practised) 2 50's + 37mm concentrated in the nose would be very effective against Zero's (when unavoidable) but mostly against the Betty's and other Japanese bombers that would be flying in to Oz.

Tomo - if you can "modify" the P-40 can I modify the AiraCobra - why not a Merlin?

MM

 

[Shortround6]

If we are allowed to use only the real planes, P-39 would've been my choice.

If we are allowed to modify (in a realistic way) either design, I'd go with P-40.
The engine position allows for non-problematic engine change (Merlin 60 series would've been no-brainer, but we can consider Bristol Hercules, R-2600, R-2800 etc), it would have been easily lightened, version with just 4 x 0.50in would've had enough fire power for fighter's job, it was regarded as a sturdy plane, and the combat range was decent.

"Merlin 60 series would've been no-brainer"

It would have required a considerable amount of work. Perhaps more than was available at the time.

Australia would have to make this decision at the end of 1941?

Merlin 60 series is still on the bench. Merlin 60 is heavier than the Merlin XX in the 40F and needs an inter-cooler stuffed somewhere in the plane. It could be done, see P-40 Q but you need an awful lot of redesign with the enemy knocking on the door. And then you are stuck with the P-40 airframe. You are stuck with it anyway in this thread but why put first rate engines in a second rate airframe?

Bristol Hercules does no good at this point in time. Engines come from England (you can forget license manufacture) and they don't have enough (unless you can kill bomber Harris).

We are already going over your 3rd engine choice and the 4th is even worse.

Have the Aussies demand P-40Fs and have done with it.

Japanese planes may be light but cutting your bomber interceptors to 4 guns doesn't seem to be the answer.

"michaelmaltby"

can I modify the AiraCobra - why not a Merlin?

What does it get you, besides production problems?

Single speed single stage Merlin isn't going to change performance that much from existing P-39.
Two speed single stage Merlin can raise your combat ceiling by around 5,000ft.
Two speed-two stage Merlin (60 series) is out. It won't fit without redesigning the plane.

 

[michaelmaltby]

"... Two speed single stage Merlin can raise your combat ceiling by around 5,000ft. "

That's better than nothing - the Zero has the unmodified P-39 at a disadvantage as it currently stands.

But I'm NOT advocating modification -- just lose the 30 cal's in the Cobra wings.

MM

 

[tomo pauk]

"Merlin 60 series would've been no-brainer"

It would have required a considerable amount of work. Perhaps more than was available at the time.

Australia would have to make this decision at the end of 1941?

Merlin 60 series is still on the bench. Merlin 60 is heavier than the Merlin XX in the 40F and needs an inter-cooler stuffed somewhere in the plane. It could be done, see P-40 Q but you need an awful lot of redesign with the enemy knocking on the door. And then you are stuck with the P-40 airframe. You are stuck with it anyway in this thread but why put first rate engines in a second rate airframe?

Of course, no Merlin 60s 'till 1943, but that's where the things would've gone likely
Till then Merlin 20s would do.

Bristol Hercules does no good at this point in time.

Same as Melin 60s, but perhaps as early as 1942.

Engines come from England (you can forget license manufacture) and they don't have enough (unless you can kill bomber Harris).

I can do that as I can alter anything in past

We are already going over your 3rd engine choice and the 4th is even worse.

Here we disagree completely

Have the Aussies demand P-40Fs and have done with it.

You can't never had enough of engine power

Japanese planes may be light but cutting your bomber interceptors to 4 guns doesn't seem to be the answer.

The issue was getting to the altitude (even for not-so-underpowered Spit V, above Darwin eg.), not that 4 x 0.50in were not enough (eg. on Wildcats).

 

[davebender]

The P-40 was perfectly capable of defeating most Japanese aircraft during December 1941. It's a fairly new design so I would expect performance improvements in future P-40 models. The P-40 was relatively easy to fly, which is critical for all those new green pilots. U.K. pilots already have considerable experience with the P-40 by December 1941 and reports have been generally favorable.

 

[Juha]

Hello
first of all, Glider, thank for the photo, I had seen previously only the original official b/w photos on ammo mags of P-39.

Difficult to say which one, Soviets thought P-39 clearly better than P-40, in Western AFs opinion was the opposite. IMHO removal of the wing armament didn't make P-39 too weakly armed against Japanese a/c, 2 heavy mgs was enough against Jap fighters and with 37mm, it needed careful maintenance to work properly with some small mods in ejection tube, Jap bombers could be rather easy targets. Soviets didn't complain, at least not much, on the cannon.
Westerners clearly liked P-40 more and at least it was easier to fly. The two heavy mgs in nose of the early P-40s was enough for Jap fighters and the later with 4-6 heavy mgs in wings had enough firepower for Jap bombers. So IMHO so-so, but I'd pick up P-39, really a subjective choice.

Juha

 

[Glider]

I don't doubt that the 37mm would be lethal against bombers of any nation, after all they don't move around much and are a lot bigger. The twin 0.5 in the nose is sufficient against early Jap fighters but some of the later ones were more robust. However if you are up against any other nation then it would be on the light side.

Give the bombers an escort and the P39 would be in trouble.

Neither did well at altitude its a question of degree. I admit to not knowing a lot about the P39's performance to be able to make a knowledgable statement.

 

[Markus]

P-40, no doubt at all. Both are faster than an A6M/Ki-43, have esentially the same engine with the same critical altitude but the P-40 has a better range and the latest version(-F) has a Merlin engine that gives her a better performance at higher altitudes. Considering the impressive altitudes the Japanese bombers operate at I´d very much like to get my hands on a few hundered P-40F.

 

[michaelmaltby]

".... Give the bombers an escort and the P39 would be in trouble...."

I'm not sure that's true. The Soviets based much of their P-39 tactics on fighting in the "vertical axis". The P-39 is faster, more powerful and a wee bit heavier than the Zero. Using the P-39 to advantage comes down to tactics - the same way that the Chenault AF used P-40 tactics against the Japanese.

Like Juha, I find my preference for the P-39 "subjective" - it's the right machine for pilots with a certain style. Yeager never fought in the P-39 but he really like to fly it.

The Russians never "officially" complained to Bell about the deadly "flat spin" but when the Soviet test pilot was in Buffalo (the story goes ) he threw a P-39 into a flat spin and then recovered.

Maybe the Russians were just "grateful" for modern, well-made stuff -

MM

 

[Shortround6]

Problems with P-39 in 1941-42 is that early installations of the 37mm were bad. Problem with ejection chute. Gun was good for 1-2 shots and then jammed.
2 synchronized .50cals is not the hottest armament. The big Browning did not take to synchronization well and rate of fire fell from around 800rpm to under 500rpm. although that does extend the firing time of 200rpg the P-39 carried.
Maybe they should leave the .30s in the wings.
Cut the .30 ammo to 400rds per gun?