XP-39 and the Claims

Koopernic · Jan 24, 2021

I recall reading the memoirs of a Luftwaffe Me 109G pilot who recalls an low altitude engagement with what the Germans thought was P51 over Italy but turned out to be P39. Several aircraft were lost on both sides.

If the P39 had of been given better engines and if it had of been retired when the P63 Kingcobra entered service in October 1943 it might have a better record. The iconinc P51B Mustang didn't start flying missions till December 1943 meaning the P51A with its altitude limited Allison was in service.

drgondog · Jan 25, 2021

Koopernic said:
Hope you're not vegetarian like my wife because I gave you Bacon. Has there ever been an analysis of what P-39 performance would have been like with say a Merlin XX (two stage Merlin used in the latter Hawker Hurricane to keep it competitive?) The P40F received this engine.

Practically speaking, the opportunity to even 'try' to install a Merlin 61 in the P-63 would have been quashed by Materiel Command based on the Priority assigned to NAA for the Mustang. That is why the P-38 was never even granted a 'try' when Cass Hough and Ben Kelsey floated the project from 8th AF Service Command in 1944.

Additionally, there was no AAF Mission for which a P-63 with fully functional Merlin 61/66 would have been superior to either P-51B/D or P-51F. The latter, with far superior performance, armament (4x20mm in interceptor role) and internal fuel for range would have been far superior to P-63 in perhaps every meaningful metric as an interceptor and very suitable for medium to long range escort (similar to P-38J pre-LE fuel cells) - and it was killed in favor of P-51H

wuzak · Jan 25, 2021

drgondog said:
Practically speaking, the opportunity to even 'try' to install a Merlin 61 in the P-63 would have been quashed by Materiel Command based on the Priority assigned to NAA for the Mustang. That is why the P-38 was never even granted a 'try' when Cass Hough and Ben Kelsey floated the project from 8th AF Service Command in 1944.

The premise was the Merlin XX into the P-39. Which would mean taking from the P-40F/L program, or from supply to the UK/Canada (Hurricane, Lancaster, Mosquito, etc.).

Probably unlikely to happen as well.

Shortround6 · Jan 25, 2021

The questions are when and why.
The P-40F prototype flew in July of 1941(?). Production started in Jan 1942.
The US was to get 3000 engines from the 9000 engine contract placed with Packard and had to use them for something. Installation in P-40 required no changes to the engine itself.

You could modify the Merlin to fit the P-39 set up but only at a cost (engineering time and testing taking how long?)
In 1942 Bell made 1932 P-39s, Curtiss built 3854 P-40s. How many fewer P-39s do you want in 1942 while Bell adapts the P-39 to the Merlin? (like new cooling systems/bigger air ducts?)

While it is quite true that the P-51B didn't go into combat until Dec 1943 the first order for the P-51B (400 planes) was placed on Aug 26th 1942, This is before the First flight is made of an A-36. On Oct 6th 1942 North American Dallas gets a contract for 1350 P-51Cs.

Using the Merlin XX in the P-39 is only going to shorten the range, maybe a little, maybe a lot. The Merlin wasn't quite as fuel effectint as the Allison (single digit percentage) but if you have several hundred more horsepower available at higher altitudes to fight with and if you use that power to have to use fuel to make that higher power. In a low altitude fight there may be little to choose in fuel consumption for our 15 minute standard but at high altitude the Merlin might be going through 20-25% more fuel per minute? I haven't looked it up It may be even more.
You can't put more fuel in the P-39 without extreme difficulty and even more weight. Bigger drop tank doesn't get you home from the fight.
P-40 held almost 20% more fuel than the P-39.

A Merlin XX powered P-39 would have performed better at high altitude than the standard P-39 (especially the 8.80 supercharger gear models) but it might not show up until late 1942.
P-40Fs didn't show up in combat until the Fall of 1942? But it might not have performed any better at low altitude or even performed quite as well. See P-40E & K vs P-40F.

If it costs both engine production and airframe production would it have been worth it?

P-39 Expert · Jan 25, 2021

Shortround6 said:
The questions are when and why.
The P-40F prototype flew in July of 1941(?). Production started in Jan 1942.
The US was to get 3000 engines from the 9000 engine contract placed with Packard and had to use them for something. Installation in P-40 required no changes to the engine itself.

You could modify the Merlin to fit the P-39 set up but only at a cost (engineering time and testing taking how long?) Merlin would need (at minimum) a new nose case without reduction gears, new engine mounts and a downdraft carb. No idea how long this would take or how much it costs. Better to put it on the P-40.
In 1942 Bell made 1932 P-39s, Curtiss built 3854 P-40s. How many fewer P-39s do you want in 1942 while Bell adapts the P-39 to the Merlin? (like new cooling systems/bigger air ducts?) Not many fewer P-39s as long as the modifications are made to the engine and not the airframe. Don't stop making P-39s with Allisons while the Merlin is modified. Again, I don't advocate putting the Merlin in the P-39.

While it is quite true that the P-51B didn't go into combat until Dec 1943 the first order for the P-51B (400 planes) was placed on Aug 26th 1942, This is before the First flight is made of an A-36. On Oct 6th 1942 North American Dallas gets a contract for 1350 P-51Cs.

Using the Merlin XX in the P-39 is only going to shorten the range, maybe a little, maybe a lot. The Merlin wasn't quite as fuel effectint as the Allison (single digit percentage) but if you have several hundred more horsepower available at higher altitudes to fight with and if you use that power to have to use fuel to make that higher power. In a low altitude fight there may be little to choose in fuel consumption for our 15 minute standard but at high altitude the Merlin might be going through 20-25% more fuel per minute? I haven't looked it up It may be even more. I haven't researched this either, but the difference in fuel consumption would be minimal at cruise. At combat power the P-39 burned about 80gph at 20000ft. A Merlin at 25% more fuel consumption would be burning about 20 more GPH or 5 gallons for 15 minutes.
You can't put more fuel in the P-39 without extreme difficulty and even more weight. Bigger drop tank doesn't get you home from the fight.
P-40 held almost 20% more fuel than the P-39.

A Merlin XX powered P-39 would have performed better at high altitude than the standard P-39 (especially the 8.80 supercharger gear models) but it might not show up until late 1942.
P-40Fs didn't show up in combat until the Fall of 1942? But it might not have performed any better at low altitude or even performed quite as well. See P-40E & K vs P-40F. Easiest way to improve 1942 P-39 performance is just remove redundant or non-essential items which could be done at forward bases. P-39D would have easily weighed 7150lbs with self sealing tanks and armor protection and a full 120gal fuel. Performance like the P-39C in wwiiaircraftperformance.org. No loss in production whatsoever.

If it costs both engine production and airframe production would it have been worth it?

Koopernic · Jan 26, 2021

The P-39 is often compared as wanting in comparison to the Me 109F/G and A6M Zero's. Both these aircraft had either variable speed or two speed superchargers. The Hurricane likewise was not considered competitive without a Merlin XX. Maybe the P-39's airframe wasn't as much a problem as a lack of a high altitude engine. It's most famous user, the VVS, tended to operate at low altitude. From an allied point of view perhaps it would have been better to utilise Merlin XX in the P-39 than the Hurricane. The Spitfire is in a league of its own in being competitive with a single stage single speed supercharger.

P-39 Expert · Jan 26, 2021

The vast majority of P-39s operated by the VVS were the later M/N/Q models with the uprated -85 engine with 9.6 supercharger gears. Their standard combat formation was the "Kuban Stairs" or "Flying Bookshelves" advocated by Alexander Pokryshkin. A normal 12 plane squadron flew a four plane flight at 5000meters (16500'), another flight at 6000m (19800') and the third at 7000m (23100') angled upsun. Not exactly low altitude, and the Luftwaffe fighters certainly had no altitude restrictions placed on them. Admittedly there were no high altitude B-17s or B-24s to escort/intercept, but not exactly down in the mud either.

tyrodtom · Jan 26, 2021

P-39 Expert said:
The vast majority of P-39s operated by the VVS were the later M/N/Q models with the uprated -85 engine with 9.6 supercharger gears. Their standard combat formation was the "Kuban Stairs" or "Flying Bookshelves" advocated by Alexander Pokryshkin. A normal 12 plane squadron flew a four plane flight at 5000meters (16500'), another flight at 6000m (19800') and the third at 7000m (23100') angled upsun. Not exactly low altitude, and the Luftwaffe fighters certainly had no altitude restrictions placed on them. Admittedly there were no high altitude B-17s or B-24s to escort/intercept, but not exactly down in the mud either.

You seem to forget why the aircraft were flying in that 3 tiered formation.
Each tier was there to provide protection for the aircraft under it.
If the aircraft in the formation below got into trouble , a aircraft from above could use the higher altitude to trade for airspeed , and enter the combat with a higher speed.
And the lowest tier was there to protect the aircraft at even lower levels , the IL-2s, Pe-2s, etc. were doing the real work.

This a standard tactic dating to the first world war, you patrol at a higher altitude, you only fight there when someone comes in ever higher and forces you to fight there.
And almost any combat maneuvering is going to result in losing altitude, so you always want to start with a altitude advantage.

P-39 Expert · Jan 27, 2021

tyrodtom said:
You seem to forget why the aircraft were flying in that 3 tiered formation.
Each tier was there to provide protection for the aircraft under it.
If the aircraft in the formation below got into trouble , a aircraft from above could use the higher altitude to trade for airspeed , and enter the combat with a higher speed.
And the lowest tier was there to protect the aircraft at even lower levels , the IL-2s, Pe-2s, etc. were doing the real work.

This a standard tactic dating to the first world war, you patrol at a higher altitude, you only fight there when someone comes in ever higher and forces you to fight there.
And almost any combat maneuvering is going to result in losing altitude, so you always want to start with a altitude advantage.

I was explaining why the eastern front was not as much of a low altitude war as many seem to think. What is your point?

Glider · Jan 27, 2021

My understanding is that because the escort is stepped up to cover lower flying aircraft, doesn't mean that the emphasis of the fighting is at a high or even medium level. The Russian airforce wasn't trained or equipped for instance to fight at at 20-30,000 ft.

It doesn't mean that they couldn't, but they didn't, and their planes tended understandably, to reflect that tactical approach of low level fighting.

tyrodtom · Jan 27, 2021

P-39 Expert said:
I was explaining why the eastern front was not as much of a low altitude war as many seem to think. What is your point?

You seem to think that their patrol height is the altitude they fight at.

In your example you've got 12 aircraft out there, but only 4 are performing the primary mission, protecting the ground attack aircraft.
The other 8 are there to protect the protectors.
The aircraft at 7000 meters certainly can't help the ground attack aircraft, they'd have to really look hard to even id camouflaged aircraft against ground cover from 4 miles up, their mission is to protect the P=39s in the lower groups.

If you don't see my point, it's because you don't want to accept that anyone else's view might have some value.

Koopernic · Jan 27, 2021

Shortround6 said:
The questions are when and why.
The P-40F prototype flew in July of 1941(?). Production started in Jan 1942.
The US was to get 3000 engines from the 9000 engine contract placed with Packard and had to use them for something. Installation in P-40 required no changes to the engine itself.

You could modify the Merlin to fit the P-39 set up but only at a cost (engineering time and testing taking how long?)
In 1942 Bell made 1932 P-39s, Curtiss built 3854 P-40s. How many fewer P-39s do you want in 1942 while Bell adapts the P-39 to the Merlin? (like new cooling systems/bigger air ducts?)

While it is quite true that the P-51B didn't go into combat until Dec 1943 the first order for the P-51B (400 planes) was placed on Aug 26th 1942, This is before the First flight is made of an A-36. On Oct 6th 1942 North American Dallas gets a contract for 1350 P-51Cs.

Using the Merlin XX in the P-39 is only going to shorten the range, maybe a little, maybe a lot. The Merlin wasn't quite as fuel effectint as the Allison (single digit percentage) but if you have several hundred more horsepower available at higher altitudes to fight with and if you use that power to have to use fuel to make that higher power. In a low altitude fight there may be little to choose in fuel consumption for our 15 minute standard but at high altitude the Merlin might be going through 20-25% more fuel per minute? I haven't looked it up It may be even more.
You can't put more fuel in the P-39 without extreme difficulty and even more weight. Bigger drop tank doesn't get you home from the fight.
P-40 held almost 20% more fuel than the P-39.

A Merlin XX powered P-39 would have performed better at high altitude than the standard P-39 (especially the 8.80 supercharger gear models) but it might not show up until late 1942.
P-40Fs didn't show up in combat until the Fall of 1942? But it might not have performed any better at low altitude or even performed quite as well. See P-40E & K vs P-40F.

If it costs both engine production and airframe production would it have been worth it?

The thing about the Merlin XX is it leads to the 1600 hp Merlin 24 which was way ahead of any single stage Allison.

P-39 Expert · Jan 27, 2021

tyrodtom said:
You seem to think that their patrol height is the altitude they fight at.

In your example you've got 12 aircraft out there, but only 4 are performing the primary mission, protecting the ground attack aircraft.
The other 8 are there to protect the protectors.
The aircraft at 7000 meters certainly can't help the ground attack aircraft, they'd have to really look hard to even id camouflaged aircraft against ground cover from 4 miles up, their mission is to protect the P=39s in the lower groups.

If you don't see my point, it's because you don't want to accept that anyone else's view might have some value.

Seems to me that all 12 planes in the squadron are protecting the ground attack aircraft. The Luftwaffe is not going to fly at low altitude just because some historian says the Eastern front was a low altitude war. I accept everyone's view on this forum.

DerAdlerIstGelandet · Jan 27, 2021

P-39 Expert said:
I accept everyone's view on this forum.

P-39 Expert · Jan 27, 2021

DerAdlerIstGelandet said:
View attachment 610394

I said I accepted everyone's view, not that I agreed with everyone's view.

tyrodtom · Jan 27, 2021

P-39 Expert said:
Seems to me that all 12 planes in the squadron are protecting the ground attack aircraft. The Luftwaffe is not going to fly at low altitude just because some historian says the Eastern front was a low altitude war. I accept everyone's view on this forum.

If they want to shoot down the IL-2 they have to get close to where it is, and it's the ground attack aircraft that is doing the damage.
Do you really think a pilot flying at 20,000 feet can pick out a camouflaged aircraft flying at ground level ?

GregP · Jan 27, 2021

About post 272 Koopernic,

The Allison V-1710-75, -77, -89, -91, & -111/113 all had 1600 hp WER. The -75 and -77 were rated at 1600 hp at 27,000 feet WER. The -111/113 were rated at 1600 hp at 28,700 feet. These were P-38 engines. These ratings were at 60.0 in. MAP. They all had 8.10 : 1 supercharger gears.

The -87 was rated at 1,500 hp at 5,400 ft. It was an A-36 engine. This was at 52 in. MAP. It has 7.48 : 1 supercharger gears.

The above had PD-12K7 and K8 carburetors.

The -109, -117, -125, & -129 were rated at 1,750 hp (75 in. MAP), 1,800 hp (76 in. MAP), and 1900 hp (75 in. MAP) for the -125/129s. The -09 and -117 were P-63 engines. Not too sure about the others ... might have been test cell ratings. They had 8.10 : 1 supercharger gears. The -109 had a PT-13E15 carb and the -117 had a PT-13E10 carb. The -125 and -129 had a PD-12K8 carb and the -129 has a PD-12K15 carb.

All of these ratings were at 3,000 rpm and I'm not sure the 70+ in. MAP levels of boost were flown by U.S. forces. Likely they were by the Soviet Union.
Note there are no P-39 engines in the above. The P-39M (-83) and N (-85) models were rated at 1410 hp at 9,500 ft and 3,000 rpm, 57 in. MAP. They had 9.6 : 1 supercharger gerars. The -83 had a PD-12K2 carburetor and the -85 had a PD-12K6 carburetor.

Shortround6 · Jan 27, 2021

Spitfires, Hurricanes and Bf 109s flew at altitudes exceeding 30,000ft during the BoB.
They didn't fight there.
It was to position themselves for diving attacks where they would have an energy advantages or to deny the enemy the advantage of a diving attack.

Once the planes started to turn the fight was going to descend

http://www.spitfireperformance.com/spit109turn.gif

Turning charts for the Spitfire I and 109E.

The Spitfire I could only sustain a 3 g turn at 12,000ft doing about 225mph. If it flew faster or slower while pulling 3 Gs it would have to descend or bleed off speed.
If it tried to pull a tighter turn it would bleed off speed.
If it was pulling less than 3 Gs at 225mph it could climb.

At higher altitudes things are going to be worse. Less lift from the wing and less power from the engine. This is the basic reason that fights that started at high altitudes (over 20,000ft) wound up much lower and even P-47s and P-51s had to spend a number of minutes climbing back up to escort altitudes after a fight.

Just because you can fly in a straight line at high speed above 20,000ft doesn't mean the plane can actual fight there except in a very limited set of circumstances.
This was one of the reasons for fitting the Merlin XX to the Hurricane II. To improve it's ability to fight at the higher altitudes.

Shortround6 · Jan 27, 2021

Koopernic said:
The thing about the Merlin XX is it leads to the 1600 hp Merlin 24 which was way ahead of any single stage Allison.

Without the altitude at which the power is made the simple listing of power is useless.

The Merlin 24 was rated at 1615hp at 2250 ft.

The engines in the P-39K and L were rated at 1580hp at 2500ft. at 60 in (15lbs or so).

glennasher · Jan 27, 2021

The Soviets and the USAAF were fighting different wars, and it's obvious that the USAAF didn't think the P-39 was suitable for the war they were fighting in Northern Europe. I think we can all agree on that. The Bell simply didn't work for the USAAF and what they wanted (and needed) to accomplish.
Since the Soviets weren't paying for the airplanes, and didn't have to take good care of them, they could fly them "balls to the wall" without any repercussions, and flew them with no regard for engine life or anything else, they simply didn't care.
Either way you look at it, they appear to be "throwaway aircraft". There's no point in making a silk purse out of a sow's ear, at least the USAAF got it.

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