Could you have designed a better P-39?

[gjs238]

With hindsight (ain't hindsight a great thing?) could you have made the P-39 a truly great plane?
Perhaps scaling-up the basic design for greater fuel capacity, better turbocharger inter/aftercooler arrangement, armament, etc?
The mid-engine layout appears to be an efficient way to incorporate a turbocharger into a single-engine fighter/interceptor (all the ducting of the P-47 is not necessary.)
The mid-engine layout also lends itself to impressive nose armament.

I'm not suggesting improving an existing P-39, rather how the basic mid-engine turbocharged design concept could have been.

 

[davebender]

Replace the Allison engine with a Packard built RR Merlin engine.

 

[Colin1]

If we're back in the day
then we're not going to find a better turbocharger solution than the one that was rejected, not without turning the fuselage into something the size of a P-47. Turbocharger design of the time was in its infancy, was not fully understood and the principal manufacturers mistrusted them, seeing them as troublesome, requiring development time and for that read an uncompetitive tender.
The P-39 could have soldiered on with the V-1710 in an Army support role superbly, it could best the Bf109E convincingly at those altitudes and could have held the line until the V-1650 came along. In an ideal world, I would have gone with an experimental Packard V-1650 installation to take the P-39 to altitude and a wet wing plus drop tanks to start working on the range issue.

So a supercharger solution, rather than a turbocharger.

In the real world, getting hold of a V-1650 would have been considerably harder, maybe buying a dozen Merlin 61s direct from Rolls-Royce and shipping them over. It is highly likely that that wouldn't have proved any easier.

 

[davebender]

We want a Army fighter aircraft that works right now. (i.e. around 1940)

1. Turborchargers are still experimental for fighter aircraft during 1940.

2. The Allison engine is a dog at all but low altitude.

3. The RR Merlin engine is state of the art and arrangements are already being made for mass production in the USA. Britain is investing heavily into further performance improvments for this engine.

Seems like a no brainer to me. Pay Packard to expand production capacity so they can produce RR Merlins for the P-39 as well as for the Lancaster bomber.

 

[gjs238]

If we're back in the day then we're not going to find a better turbocharger solution than the one that was rejected, not without turning the fuselage into something the size of a P-47. Turbocharger design of the time was in its infancy, was not fully understood and the principal manufacturers mistrusted them, seeing them as troublesome, requiring development time and for that read an uncompetitive tender.

How is that? (not a challenge, just a question)
Turbos were accepted and worked out well in several US aircraft. With more room why wouldn't a turbo work in an enlarged P-39?
I know this is apples oranges by a long shot, but a modern front-engine car doesn't have the turbo located back in the trunk connected by ductwork ala P-47, the turbo is up front w/the engine (or down back if a rear or mid-engine setup.)

 

[Colin1]

3. The RR Merlin engine is state of the art and arrangements are already being made for mass production in the USA. Britain is investing heavily into further performance improvments for this engine.

Seems like a no brainer to me. Pay Packard to expand production capacity so they can produce RR Merlins for the P-39 as well as for the Lancaster bomber.

With Merlin production going to the Lancaster and later the Mustang, how easily do you think the Bell lines are going to procure them?

Once the Merlin Mustang shows its colours as a high-altitude, long-legged escort, who do you think is going to look at the low-altitude, short-legged Bell fighter? The USAAF had their Mustang, they didn't need another one, just like they didn't need the Curtiss XP-40Q.

I'd definitely look at a V-1650 installation, the problem still might be getting hold of one.

 

[Colin1]

...a modern front-engine car doesn't have the turbo located back in the trunk connected by ductwork ala P-47, the turbo is up front w/the engine (or down back if a rear or mid-engine setup.)

I'll answer more fully in a minute, I'm busy with something but a car's turbo isn't being driven by a 27 - 36 litre engine

 

[gjs238]

With Merlin production going to the Lancaster and later the Mustang, how easily do you think the Bell lines are going to procure them?

Once the Merlin Mustang shows its colours as a high-altitude, long-legged escort, who do you think is going to look at the low-altitude, short-legged Bell fighter? The USAAF had their Mustang, they didn't need another one, just like they didn't need the Curtiss XP-40Q.

I'd definitely look at a V-1650 installation, the problem still might be getting hold of one.

- Merlin Mustang?
- XP-40Q?
- V-1650?
All too late.
I'm talking about a response to USAAC Circular Proposal X-609 in February 1937.
The P-39 as we know it first flew (according to Wiki) 6 April 1938.

Turn the clock back to February 1937.
Could what became to be known as the P-39 have turned out "better, faster, stronger?"

 

[Shortround6]

- Merlin Mustang?
- XP-40Q?
- V-1650?
All too late.
I'm talking about a response to USAAC Circular Proposal X-609 in February 1937.
The P-39 as we know it first flew (according to Wiki) 6 April 1938.

Turn the clock back to February 1937.
Could what became to be known as the P-39 have turned out "better, faster, stronger?"

.

Better? possibly.
Faster? at what altitude? under 15,000ft no. over 20,000ft yes.
Stronger? never knew the P-39 was weak

Enlarging the basic design to house an adequate inter-cooler (the basic failing of the original design) and more the fuel ( the 2nd failing) are both going to require a bigger, heavier airframe. The turbo is going to provide NO additional HP at the lower altitudes and only give you superior power from around 15,000ft and up. With the same power and a bigger airplane speed and climb will both be inferior until the planes reach a height at which the turbo installation offers a better power to weight/power to drag ratio than the non-turbo plane. Probably somewhere over 20,000ft. The time to altitude of the larger airplane might be suspect also. With a lower climb rate at the lower altitudes, what altitude do the planes have to climb to for the turbo plane catch up?

 

[MikeGazdik]

I agree with Davebender, put the Packard Merlin in the plane and your are done, other than range.

If we take the time-line back to 37-38, well then I again look at both Allison and the USAAC needing to install an altitude capable supercharger on the V-12 they had in production. That not only changes the game for the P39, but the P-40 as well. ( and even possibly the P-38 )

And like mentioned, wet wings for the Bell would have been critical for range as the fuselage is used up with the cannon, nose gear, engine and , radiator.

I would rather do that instead of increase the size of the plane to accept fuselage fuel or to facilitate the turbo-charger. I think the P-39 really was an aerodynamically clean airframe for its time. I wonder what the speed at say 25k feet would have been with a Merlin? I would guess in the 415mph range !

 

[Demetrious]

And like mentioned, wet wings for the Bell would have been critical for range as the fuselage is used up with the cannon, nose gear, engine and , radiator.

Be careful with that. Range is very important, but wet wings (that don't use sealing tanks) make for reduced survivability, and the weight penalty can be significant.

 

[riacrato]

Put an armor piercing cannon in it, call it an attacker and you're done.

 

[davebender]

how easily do you think the Bell lines are going to procure them?

No problem at all if the U.S.Army Air Corps makes money available. Hundreds of American military- industrial complexes were built from scratch during the late 1930s to early 1940s. Pour a hundred million dollars on the ground in 1940 and you have a state of the art RR Merlin aircraft engine plant working at design capacity by 1942.

Personally I'd use the new Merlin engines for P-38s, P-40s and P-51s rather then the P-39. But that is an an entirely different issue. Someone in the U.S. Army Air Corps procurement branch was convinced the P-39 was a great fighter aircraft. Switching to the Merlin engine will help some. At least nobody will be able to claim the P-39 was given a poor engine.

 

[Milosh]

Why would switching to the Merlin be an improvement? There was no Merlin 60 series engines at the time.

 

[delcyros]

[+] reduce wing area. =increase top speed and roll rate. Accept the higher wingloading.
[+] install either LE-slats or slots for the outer wing panels = improve low speed handling, less prone to spin violently from near stall conditions.
[+]replace the 37mm nose cannon by a .50cal BMG. Replace wing LMG´s by .50 cal BMG´s. = lowering the loaded weight and easening gun firing by a uniform BMG calibre weapon, typical for US practice.
[+]install thrust producing ejector nozzles = increase top speed further.
[+]install a reflector type gunsight instead of the telecope type. Replace it later with computing gunsights, if aviable.

All suggestions are possible in the timeframe and do not require major changes or technology still under development. The resulting plane will not only be significantly faster in top speed, it will also enjoi a lower weight and thus better acceleration, a uniform and more precise gun laying distribution and improved maneuverability on the longitudinal axis traded for a wider turn radius. More importantly, it will be easier to fly close to the stall speed regime.

 

[krieghund]

The YP-39 during testing at Wright-Pat during 1939 reached 390 at 20kft (of course armament was not fitted) It was estimated that with armament and war kit it would have reached 375 at 20kft.

The V1710-17 with B-5 Turbo was rated at 1000 HP at 20kft. Later with turbo adjustments it was rated at 1000 at 25kft which by my estimations would put at around 380-385 at 25kft climbing to 20kft in 6 minutes with a range of about 600 miles. However the Army changed all that.

(A note about the Merlin: The V1650-1 in the P-40F was not real improvement over the V1710-85 models)

The armament would have been 1x37, 2x.50 and 2x.30 all in the nose as in the P-39C. I would have opted for all five guns to be .50 cal. to solve the aiming problems in a deflection shot.

The real fix to the P-39 is the P-63 Kingcobra. the P-39 is too small and has no growth potential.

 

[riacrato]

[+]replace the 37mm nose cannon by a .50cal BMG. Replace wing LMG´s by .50 cal BMG´s. = lowering the loaded weight and easening gun firing by a uniform BMG calibre weapon, typical for US practice.

I got the feeling that would completely off-balance the plane. Also the cannon was the whole purpose of this thing.

 

[davebender]

The real fix to the P-39 is the P-63 Kingcobra. the P-39 is too small and has no growth potential.

In other words, scrap the design and start over with something better.

Perhaps Bell could purchase rights to license build the He-112B and DB601 engine. You get an overall better aircraft and can fire the 37mm cannon through the prop hub. 8)

 

[krieghund]

You meant the He100D?

 

[timshatz]

[+] reduce wing area. =increase top speed and roll rate. Accept the higher wingloading.
[+] install either LE-slats or slots for the outer wing panels = improve low speed handling, less prone to spin violently from near stall conditions.
[+]replace the 37mm nose cannon by a .50cal BMG. Replace wing LMG´s by .50 cal BMG´s. = lowering the loaded weight and easening gun firing by a uniform BMG calibre weapon, typical for US practice.
[+]install thrust producing ejector nozzles = increase top speed further.
[+]install a reflector type gunsight instead of the telecope type. Replace it later with computing gunsights, if aviable.

All suggestions are possible in the timeframe and do not require major changes or technology still under development. The resulting plane will not only be significantly faster in top speed, it will also enjoi a lower weight and thus better acceleration, a uniform and more precise gun laying distribution and improved maneuverability on the longitudinal axis traded for a wider turn radius. More importantly, it will be easier to fly close to the stall speed regime.

Like all of them Decl except the 50 cal in the wing and nose. Take the guns out of the wings and add a 20MM to the nose. It will be almost identical to the 109F/G in armament and they did pretty well with that (and very similar to the Yak3). Actually, now that I think about it, maybe the Soviet 23MM cannon would be a better call. I've read on this board that it was superior to the 20MM (at least I think it was this board).

Otherwise, go with it. Especially like the leading edge slats and wing area ideas. Always thought the wings were a tad small on the P39 but if you can shave more off, all the better.