Another 10000 P-36/40 aircraft?

[Thumpalumpacus]

 

[ThomasP]

The info below is from 1942 A&AEE tests

P-39D-1 (7830 lbs)
Vmax_(3000 rpm at 42"Hg) 355 mph at 13,000 ft
ROC_ (2600 rpm at 37"Hg) 2040 ft/min
SC___(2600 rpm at 37"Hg) 29,000 ft

P-40D,E/Kittyhawk Mk I (8480 lbs)
Vmax_(3000 rpm at 42"Hg) 332 mph at 14,500 ft
ROC_ (2600 rpm at 37"Hg) 1640 ft/min
SC___(2600 rpm at 37"Hg) 28,700 ft

The info below is from 1943 USAAF tests

P-39Q (7870 lbs) w/o wing guns
Vmax_(3000 rpm at 55"Hg) 385 mph at 11,000 ft (actually from P-39N test)
ROC_ (3000 rpm at 37"Hg) 2500 ft/min
______(3000 rpm at 55"Hg) 3470 ft/min
SC___(3000 rpm at FT"Hg) 34,900 ft

P-40F/Kittyhawk Mk II (8450 lbs) with bomb shackle and sway braces
Vmax_(3000 rpm at 48"Hg) 365 mph at 18,500 ft (374 mph clean)
ROC_ (3000 rpm at 48"Hg) 2250 ft/min
______(3000 rpm at 60"Hg) 3090 ft/min
SC___(2850 rpm at FT"Hg) 34,000 ft

 

[SaparotRob]

Remove the nose armor.

 

[wuzak]

I wonder why they never put any Merlin's in P-39s?

I'm really curious, why didn't they ever put a Merlin 20 in a P-39? Seems like that could have been a good fit.

Because:
The Merlin 20-series used updraft carburettors, the V-1710 downdraft. That means that the intake would be through the floor of the P-39.

The Merlin had part of the reduction gear case built into the crankcase. It was not as modular as the P-39, so changing to a remote gearbox system wasn't as easy.

 

[Schweik]

The info below is from 1942 A&AEE tests

P-39D-1 (7830 lbs)
Vmax_(3000 rpm at 42"Hg) 355 mph at 13,000 ft
ROC_ (2600 rpm at 37"Hg) 2040 ft/min
SC___(2600 rpm at 37"Hg) 29,000 ft

P-40D,E/Kittyhawk Mk I (8480 lbs)
Vmax_(3000 rpm at 42"Hg) 332 mph at 14,500 ft
ROC_ (2600 rpm at 37"Hg) 1640 ft/min
SC___(2600 rpm at 37"Hg) 28,700 ft

The info below is from 1943 USAAF tests

P-39Q (7870 lbs) w/o wing guns
Vmax_(3000 rpm at 55"Hg) 385 mph at 11,000 ft (actually from P-39N test)
ROC_ (3000 rpm at 37"Hg) 2500 ft/min
______(3000 rpm at 55"Hg) 3470 ft/min
SC___(3000 rpm at FT"Hg) 34,900 ft

P-40F/Kittyhawk Mk II (8450 lbs) with bomb shackle and sway braces
Vmax_(3000 rpm at 48"Hg) 365 mph at 18,500 ft (374 mph clean)
ROC_ (3000 rpm at 48"Hg) 2250 ft/min
______(3000 rpm at 60"Hg) 3090 ft/min
SC___(2850 rpm at FT"Hg) 34,000 ft

Interesting, do you have a link to the source or the doc number etc.?

The 1943 test seems a little beneficial to the P-39 since they took the wing guns out, but put bomb shackles on the P-40F, but it's about right I think. And certainly most P-40s were flying with bomb shackles in the field. If they lightened it ala P-40L style (removing two wing guns + their ammunition, some front armor, and the forward fuel tank) it improves a bit more, losing about 500 lbs. A British test clocked a "Kittyhawk II" at 370 mph at 20,000 ft with shackles and sway braces. Still slower than a P-39Q though.

Wing loading on that P-39Q is 36.9 lbs, for the P-40F at your loading it's 35.8. For the lightened version it's 33.8. The P-40 had bigger wings and could turn a bit better.

P-40 could also roll a bit better which maybe matters more.

I'm not sure which was faster in a dive but the P-40 was able to do that escape maneuver effectively both against Japaense and German / Italian fighters, which is one of the reasons pilots liked it.

Then there is the handling issue. Which perhaps boils down to a combination of training and some kind of field modifications. But they didn't have time for that in 1942, nor did they figure it out in 1943 either. Only the Soviets seem to have solved this problem.

All in all that's why you have 1 US Ace flying P-39s, vs 86 US Aces (including 11 double Aces) flying P-40s, plus another 46 British / Commonwealth pilots (including 7 double aces). Hence the speculation if they could have built more P-40s in the OP.

 

[Schweik]

Because:
The Merlin 20-series used updraft carburettors, the V-1710 downdraft. That means that the intake would be through the floor of the P-39.

The Merlin had part of the reduction gear case built into the crankcase. It was not as modular as the P-39, so changing to a remote gearbox system wasn't as easy.

Thanks! Forgive me if this is a stupid question, but couldn't they have inverted the engine or plumbed the intake? I guess it was too much to sort out in time... a Merlin engined P-39 would have been potentially formidable.

 

[Shortround6]

Thanks! Forgive me if this is a stupid question, but couldn't they have inverted the engine or plumbed the intake? I guess it was too much to sort out in time... a Merlin engined P-39 would have been potentially formidable.

Merlin 23 but close enough.

Carb is at bottom right. Supercharger is a bit bigger in diameter than an Allison supercharger.
You can see where the nose gear casing split is. Yes you could probably have put a blanking plate on it.
However with any major changes you have to get a test engine to complete a 150 hour type test.
You also have to make sure that the drive system is compatible with the Merlin's vibration characteristics. And several variations, like 1 or 2 cylinders missing firing at high power not causing problems with the 10 ft drive shaft.

None of this is impossible, it just isn't as easy as it might appear and perhaps the engineering time could be better spent somewhere else.

Like Packard was just hitting their 800 a month production target about the time the USAAF was starting to order P-51Bs with two stage Merlins which was several months before the prototype actually flew.

Hmmm, P-39 with two speed Merlins in the fall/winter of 1942/43 and P-51s with two stage superchargers delayed 3-6 months?

Edit, flipping the engine over would require modifications to the cooling system and oil system. Which would need extensive testing.

 

[Schweik]

Some merlins had gravity fed carbs too right? But not the XX?

 

[Shortround6]

Some merlins had gravity fed carbs too right? But not the XX?

I think we have some confusion here.
All Merlins were were feed by pressure pumps to the carburetor. Just like most cars with carbs are feed by fuel pumps. Doesn't mean the early Melrins or a car will run inverted for very long.

Some WW I and 1920s aircraft were "gravity" fed with fuel tank/s in or on the upper wing.

However this has nothing to do with the famous Merlin cutting out when going into a dive problem.
That was an internal carburetor problem and had to do with the carburetor float being pushed out of position under negative "G"s and affecting the fuel feed from the float bowl to the carburetor jet/s.

what were called pressure feed carbs were actually much closer to single point fuel injection. No float bowls.
Some XX engines had the old carbs and some had the new bowls with restrictor plates, it depends on date of manufacture and refit state.

 

[Schweik]

Gotcha, interesting thanks

 

[P-39 Expert]

But did they?
No, they did not.

The USAAF desperately needed something to wrest air dominance from Japan and didn't have the luxury of time to eff with experimental combinations that might find the magic combination in order for it to work.

At least the USAAF used it until they got the P-38 in operational number, the RAF dumped it on the Soviets as fast as they could.

Yes they did, in September 1942. Said they would now operate at 27000'. Plenty high enough to combat the Japanese.

 

[SaparotRob]

Only it didn't.

 

[GrauGeist]

Yes they did, in September 1942. Said they would now operate at 27000'. Plenty high enough to combat the Japanese.

Sorry, but the P-39D and D-1 were not high altitude champs and from late spring to September of that year was not enough time to figure out the P-39's quirks.
Even the XP-39E, flown by a career test pilot, was destroyed by a flat spin.

Oh, there was also the P-400 in the theater during that time span - it was affectionately referred to as a "P-40 with a Zero on it's tail"...

 

[ThomasP]

Hey Schweik,

I think all the A&AEE test data is available on the "WWII Aircraft Performance" site.

I do not remember if all the USAAF test data is available on the same site, but some of it is. I think that all the rest is from the respective aircraft's TOCL (Take Off, Climb, Landing) charts in the Pilot's manuals.

 

[P-39 Expert]

Interesting, do you have a link to the source or the doc number etc.?

The 1943 test seems a little beneficial to the P-39 since they took the wing guns out, but put bomb shackles on the P-40F, but it's about right I think. And certainly most P-40s were flying with bomb shackles in the field. If they lightened it ala P-40L style (removing two wing guns + their ammunition, some front armor, and the forward fuel tank) it improves a bit more, losing about 500 lbs. A British test clocked a "Kittyhawk II" at 370 mph at 20,000 ft with shackles and sway braces. Still slower than a P-39Q though.

Wing loading on that P-39Q is 36.9 lbs, for the P-40F at your loading it's 35.8. For the lightened version it's 33.8. The P-40 had bigger wings and could turn a bit better.

P-40 could also roll a bit better which maybe matters more.

I'm not sure which was faster in a dive but the P-40 was able to do that escape maneuver effectively both against Japaense and German / Italian fighters, which is one of the reasons pilots liked it.

Then there is the handling issue. Which perhaps boils down to a combination of training and some kind of field modifications. But they didn't have time for that in 1942, nor did they figure it out in 1943 either. Only the Soviets seem to have solved this problem.

All in all that's why you have 1 US Ace flying P-39s, vs 86 US Aces (including 11 double Aces) flying P-40s, plus another 46 British / Commonwealth pilots (including 7 double aces). Hence the speculation if they could have built more P-40s in the OP.

I've posted this chart before. All information from wwiiaircraftperformance.org. The P-40F is in blue from a test dated July 1942. The P-39K graph is dated May 1942. P-39K performance is almost exactly the same as P-39D performance dated December 1941. Red dots estimate P-39 climb at 3000rpm. P-40F climb is at 2850rpm.

P-39D/K is faster below 20000', about the same above. P-39D/K climbs better below 20000', about the same above if P-40F uses 3000rpm.

Allison P-40E speed was 340mph at 15300' and climb was about the same as the P-39D/K WITH A DROP TANK.

 

[special ed]

Lucy just pulled the football away from Charlie Brown's kick again.

 

[Shortround6]

To quote Yogi Berra "It's deja vu all over again"

 

[Schweik]

I've posted this chart before. All information from wwiiaircraftperformance.org. The P-40F is in blue from a test dated July 1942. The P-39K graph is dated May 1942. P-39K performance is almost exactly the same as P-39D performance dated December 1941. Red dots estimate P-39 climb at 3000rpm. P-40F climb is at 2850rpm.

P-39D/K is faster below 20000', about the same above. P-39D/K climbs better below 20000', about the same above if P-40F uses 3000rpm.

Allison P-40E speed was 340mph at 15300' and climb was about the same as the P-39D/K WITH A DROP TANK.

I've read (and downloaded) every document available on WW2AircraftPerformance.org on the P-39 and P-40 (and several other planes). I was asking ThomasP for a document link or doc number because I don't have any document on the specific test ThomasP seems to have referred to for the P-40F, and if it was available I'd like to add it to my archive. His numbers basically match my own from secondary sources, but I'd still like to find the primary source for that 1943 test if it exists. I also have flight manuals for every version of the P-40 (and for several other aircraft, including two versions of the P-39).

I am always interested in any primary sources I don't already have. I'm not interested in your interpretation or analysis, no offense but your subjective analysis is obviously not credible on this issue and your opinion is already very well known here. You are obviously deeply invested in a rehabilitation of this aircraft - as I've said many times, the combat histories speak for themselves in this regard. Good luck in your attempts but I'm not going to engage with you on P-39 vs anything.

I am not averse to thread drift and have often contributed to it myself many times but it's clearly time to give a rest to the P-39 hijacking, you are not helping your cause so to speak, in fact very much to the contrary.

 

[DerAdlerIstGelandet]

You keep leaving out the prime user of the P-39. The Soviets defeated the LW at the height of their power at all altitudes and all conditions. From mid 1942 until the end of the war. The Soviets produced over 67000 fighter planes but half of their top ten aces flew the P-39 with less than 5000 units supplied to them. The historical record is what it is.

Why do you keep hijacking every thread with the P-39?

 

[DerAdlerIstGelandet]

The AAF could have easily lightened them just like the Soviets.

You have repeated this dribble in countless other threads. You have a dedicated P-39 thread so that you don't have to take over other threads.

It is getting really tiring and old.