USN air combat data from Office of Naval Intelligence

[TheElf]

Hi, Dans 'facts' have the Zero achiving it's fastest speed at 14,930
with the P-39 getting it's fastest speed at 13,800

Where do you get the 10k for P-39D disadvantage? The Manual says "high altitude" I don't think 10k is considered high (I'm thinking the P-39 problem is at 20k...well over 15k at least. In testing the results at 9k and 15k were the same)

When I want to beat up P-39s in UV I set the bombers to 16k and my Zeros to 17k (then the P-39 have to climb while I can dive)

To be clear the manual says,"For every 1k' above 10k' the P-39/400 loses one maneuver point not to exceed 9 maneuver points." This would mean that at 19k' the penalty would cease being applied, and ALL P-39/400's would operate at their maneuver rating -9. ---The Manual 20.4 High Alt Combat P.60

Elf

[mogami]

Hi Ok thanks, So 10k normal 11k -1, to 19k - 9 And TJ thinks it should start at 14k rather then 11k OK no problem. And the whole issue is the super charger (or lack of one)

(If the ac achived it's fastest speed at 13,800 I'd say being minus below that was incorrect.)

Should not be too hard to fix.

[TheElf]

More gouge on the P-39 From the NASM (National Air and Space Museum)Website http://www.nasm.si.edu/nasm/aero/aircraft/bellp39q.htm

"Even more damning, NACA advised the Air Corps to remove the turbo-supercharger, and it apparently agreed, believing that an engine with a geared supercharger was close at hand. However, Allison was years away from fielding such a powerplant and when it did, newer and more advanced airframes became the logical recipients. Without this vital component, the P-39 became unsuitable for combat above about 6,080 m (20,000 ft).

With war clouds gathering, the Air Corps contracted with Bell for eighty production airplanes designated the P-39C (twenty airplanes) and the P-39D (sixty airplanes). To supplement the cannon, Bell armed the P-39C with two .50 and two .30 caliber machine guns mounted in the upper nose cowling to fire through the propeller. The company relocated the .30 caliber gun battery to the wings and doubled their number on the P-39D. Foreign air forces, debilitated by years of fiscal neglect, frantically bought up the first Airacorbras. In 1940, the French and the British each signed contracts for hundreds of export Airacobras. The order came too late for the French and the British found nothing to like in the P-39 so many of these airplanes were redirected to the Air Corps and redesignated as P-400s. The British Government sent most its P-39s to the Soviet Union. The Army Air Corps had absorbed 179 Airacobras destined for England and most of these fighters went into action in the Pacific Theater with the 8th Pursuit Group at Port Moresby, New Guinea, in April 1942. For the next year-and-a-half, the best fighter aircaft the United States could field were P-39s and Curtiss P-40s"

A P-400 is just a P-39D that had been repossessed after the Brits poo-poo'd the entire aircraft. Among the 19 deficienceies they found...lethal Carbon Monoxide concentration in the cockpit after firing the guns, random errors in the compass after firing the cannon, and an unacceptably long takeoff roll of 2250'(686m)

Elf

[TheElf]

A P-400 is just a P-39D that had been repossessed after the Brits poo-poo'd the entire aircraft. Among the 19 deficienceies they found...lethal Carbon Monoxide concentration in the cockpit after firing the guns, random errors in the compass after firing the cannon, and an unacceptably long takeoff roll of 2250'(686m)

Forgot...this comes from "American warplanes of WWII". Edited by David Donald, 1995 Aerospace Pub. Ltd.

[mogami]

Hi, Well things are coming together. It all makes sense because the super charger is for thinner air so above 20k the P-39D would suffer. But that being the case and since I can't find too many combats at or over 20k (and the Soviets kept 2 P-39 groups as fighters till 45) Then the poor P-39D was simply out classed by the Japanese over Port Moresby (and the Canal) At any altitude.
(I was intersted in one of Mdiehls reports that had P-400 in combat after the date I had seen the USAAF forbid them from dogfighting) Also I thought the P-400 was armed differently then P-39D.

The penalty should be above 20k and likely there are plently of other aircraft from both sides that should also suffer from it. How high can an open cockpit aircraft fly?

[TheElf]

Thought this might help. Came from Mike Wood on the UV forum back in MAR 02. Pretty interesting. I wonder, does the info below mean that Zeros CAN't make slashing attacks? If so I think this is a mistake

You might notice that some aircraft perform better in some circumstances than other, in the game. Pilot/air crew experience is always the most important factor in the air war, in Uncommon Valor, but experience can be somewhat offset by the flight characteristics and capabilities of the aircraft.

COMBAT AIR PATROL

In this game, the most important characteristic for combat air patrol (CAP) is climb rate. Normally, only a couple to a few aircraft are in the air at once. When enemy aircraft are spotted by those aircraft that are airborne or by radar or ground forces assigned to watch for enemy aircraft, all planes available for CAP are scrambled. The altitude at which CAP is assigned is not important in the game, as all aircraft will end up at the same altitude, +-3000 feet of the enemy bombers. But, planes being scrambled have to get up to that altitude. A high climb rate allows the fighters to climb to combat altitude before the bombers arrive at the target. Other factors include the experience of the pilots, the skill of the squadron commander, the moral and fatigue of the squadron, the presence of friendly radar and the weather. The higher the climb rate, the more aircraft that will be able to intercept in the incoming force.

AIR TO AIR COMBAT

In this game, once aircraft have closed for combat, the most important factors include maneuverability and speed. If a plane has a significantly higher maneuverability, the pilot will try to dogfight. If the plane has a significantly higher speed, the pilot will try to make slashing attacks. If the pilot succeeds or no is primarily dependent on his skill. So, you will find that a trainer, such as the Wirraway, will suffer horribly against a high performance fighter, such as a Zero. The Zero is much faster and far more maneuverable. The only saving feature of the Wirraway, in such a case is the rear firing gunner. The Wildcat is also in trouble, as it is not any faster than the Zero, and is less maneuverable to boot. The Kittyhawk, on the other hand, is significantly faster and quite durable. The Kittyhawk pilot will try for slashing attacks, using speed to fly by very quickly, fire his guns and then dive or make a very lazy turn around and come back. He also can go head to head with the Zero and stand a good chance of living to tell the tale. Later war Allied aircraft, such as the Lightning, Thunderbolt or Corsair are adequately maneuverable and extremely fast and rugged. Very few Japanese aircraft can stand up to these. Pilot experience determines, of course, if the desired tactic can be achieved and squadron commander's air skill is influential. If the tactic is not known to the pilots, they will not use it well. Fatigue and morale are also important.

BOMBERS

Endurance, speed and bomb load are very important to the bomber. Aircraft such as the Flying Fortress, have almost no maneuverability and will usually become damaged on the mission, if opposed by interceptors or anti-aircraft artillery. But, big bombers are lost more on landing with damage, than in air to air combat. Smaller, faster aircraft, such as the Havoc, might be fast enough to avoid the better part of the flak and can maneuver against interceptors. This allows medium bombers, like the Mitchell, to fly unescorted missions against the Japanese with an acceptable loss rate. Bombers without self-sealing fuel tanks, with low endurance, speed and only moderate firepower, such as the Nell will suffer losses much higher than replacement rate, if unescorted and opposed. Bomb load is important, because it means more bomb damage and fewer missions being flown over the same target.

ALTITUDES

If opposing bombers or flying close escort, the fighter altitude is determined pretty much by the bomber altitude. Altitude within the +- 3000 feet of the bombers is determined more by pilot and squadron leader skill and aircraft speed than by assigned altitude. The Airacobra, lacking a super-charger, does not perform well at high altitudes. To take advantage of this, the Japanese player might make a high altitude fighter sweep. This would simulate high cover. Otherwise, the escorts will fly close cover. The higher the bomber, the less chance it will take damage from anti-aircraft artillery. But, with higher altitude, the chance of hitting any thing is reduced.

RANGE

Pilots and crews become fatigued as the fly. A long mission will cause them to end up with a high fatigue and disruption rate, upon arriving at the target. Flying a Zero from Rabaul is much more tiring than flying from Lae and squadron performance suffers accordingly.


Hope this Helps...

Michael Wood

Last edited by Mike Wood on Tuesday at 0312 PM 26 Mar 02 .
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PS. Mogami we need to get together sometime here in Va Bch and talk shop face to face

[mogami]

Hi, Sorry Elf I am in Charleston SC now.

[TheElf]

Hi, Well things are coming together. It all makes sense because the super charger is for thinner air so above 20k the P-39D would suffer.

I think if you read that piece from NASM is says that the P-39D became "unsuitable for combat above 20K' ". I think it would be reasonable to infer that above that altitude it was really bad, and it wasn't that at 20K' that it's performace hit a "wall" and began to degrade, but it was a gradual progression starting lower and becoming impossible above 20k'. Therfore I think this graduated progression is pretty **** accurate on 2x3's part(I can't wait to hear from TJ on this ) In fact, an Axis Fan-boy might argue that they may have been a bit lenient as there is no further panalty or even a "No can do" restriction above 20K.

But that being the case and since I can't find too many combats at or over 20k (and the Soviets kept 2 P-39 groups as fighters till 45) Then the poor P-39D was simply out classed by the Japanese over Port Moresby (and the Canal) At any altitude.

The Russians really liked the P-39. Primarily as an Ground support Aircraft. The 37mm cannon was the same size as their main battle tank in 39-42, the Pz III series. They also took order of the P-39Q, a marked improvement over the D. I could look up the improvements but its late and I don't feel like it. Maybe 2morrow. I believe the 2 grps of P-39s in late 45' you are refering to were probably the Q model.

(I was interested in one of Mdiehls reports that had P-400 in combat after the date I had seen the USAAF forbid them from dogfighting) Also I thought the P-400 was armed differently then P-39D.

I'm pretty sure you're right. I believe the 37mm was deleted. I looked but couldn't find where I read about that. Maintainers hated the thing. Had to pull the engine to work on it! Pilots found it difficult to fire accurately, and it frequently jammed. Not to mention the weight.

The penalty should be above 20k and likely there are plently of other aircraft from both sides that should also suffer from it. How high can an open cockpit aircraft fly?

I disagree. See above

If the pilot is wearing an O2 mask, sky's the limit. The Navy uses 14k as a no kidding altitude for no O2. I have a pressurized cockpit and frequently let my mask dangle above 14k. Gotta hawk the cabin altimeter though. Don't tell anyone.

[TheElf]

Hi, Sorry Elf I am in Charleston SC now.

Did you move??

[mogami]

Hi, Yes, I just can't sit still.

I know the Soviets liked the Iron Dogs for ground attack but they also kept those two groups as fighters. Seems they had plently of low level air combat.
I was never sure where pilots went on oxygen. How much does an aircraft carry? (would long flights like Rabaul to Guadalcanal force Japanese to fly below 14k part of the way to have enough oxygen for when they went higher closer to target?)

[Tristanjohn]

To be clear the manual says,"For every 1k' above 10k' the P-39/400 loses one maneuver point not to exceed 9 maneuver points." This would mean that at 19k' the penalty would cease being applied, and ALL P-39/400's would operate at their maneuver rating -9. ---The Manual 20.4 High Alt Combat P.60

Elf

That's right. The penalty begins at above 10,000 feet, running up, in increments of a thousand feet, to 20,000 feet. Point is this reflects doubly-confused thinking on the matter as it doesn't recognize the "Zero's" own deficiency's as altitude increased above 12,000 feet while completely botching the P-39's flying characteristics with regard to its own actual issues with altitude.

It's a gross error by any barometer.

[TheElf]

Hi, Yes, I just can't sit still.

I know the Soviets liked the Iron Dogs for ground attack but they also kept those two groups as fighters. Seems they had plently of low level air combat.
I was never sure where pilots went on oxygen. How much does an aircraft carry? (would long flights like Rabaul to Guadalcanal force Japanese to fly below 14k part of the way to have enough oxygen for when they went higher closer to target?)

Not sure. I just read an excerpt from Frank over on Mdiehls thread. In it the P-400s that were participating in a co-op CAP with Marine F4F's didn't even have O2 on board. Possibly a supply issue? Dunno. They capped at 15k'. Back in WWII I'm sure all they had was Liquid O2(but that's without researching it). It would have been kept in a Spherical container somewhere near the cockpit. It was limited in supply aboard an airplane. But think of the B-17s and P-51's who flew 8 hour missions at hi Alt. They must've had enough for at least that long. I would assume that given the limitations of the system pilots put it on above 14-15k' and took it off below.

It wasn't until the last 10 years or so that Our Hornets got OBOGS (On Board Oxyen Generation Sytem) A veritable endless supply of O2 from our bleed air system. Some FA-18A's and low lot C's still use LOX.

[Daniel Oskar]

The P-400 was a little more of a dog than the P-39. It had a different engine than many of the P-39Ds, the Allison V-1710-35 rated at 1150 hp. Many of the P-39D models in use on the 'canal had the V-1710-63 rated at 1325hp.

[TheElf]

That's right. The penalty begins at above 10,000 feet, running up, in increments of a thousand feet, to 20,000 feet. Point is this reflects doubly-confused thinking on the matter as it doesn't recognize the "Zero's" own deficiency's as altitude increased above 12,000 feet while completely botching the P-39's flying characteristics with regard to its own actual issues with altitude.

It's a gross error by any barometer.

On May 20 we fought the highest air battle in our history, when CDR Nakajima led 15 Zeros into the enemy zone at Moresby at a height of 30,000'. It took us an hour and 20 min. to reach Moresby from Lae. We relied on our height to give us the advantage of suprise, and were astonished to encounter an enemy formation several miles ahead of us at the same altitude.
I was doubtful of the Zero's ability to perform aerobatics at this height. My personal record height witht the Zero was 37,720 feet, acheived with an O2 mask and an electrically heated jacket. At that height the plane was extremely sluggish at the controls, and refused to climb another foot. Consequently, it seemed unwise to fight with the Zero at a height of 30,000'(he isn't saying he would DIVE from 30,000 though )
There were 10 enemy fighters, apparently P-39s of a new design(personally I think they may have been P-40s ). I led the attack and was at once engaged. The 14 other Zeros met the head-on attack of the remaining planes.
The controls were sluggish in the thin air. As the other plane came at me, I tried for an advantageous position from which to fire. We seemed almost to be moving in slow motion. I kept edging clser to the other fighter in a tight spiral, and maneuvered for a quick burst. I yanked the stick over hard--too hard!"

-----At this point Sakai's mask falls off and he blacks out. He doesn't pass out, he blacks out. Not unconciousness, but much like the intial stages of G-LOC when sight is lost. he regains his vision at 20k(keep this altitude in your back pocket)------

"...,I was at 20k, the plane still under control.
I snapped out of the turn instantly, for it was likely that the Airacobra had followed me down and was setting me up for the kill. but the other plane was also in trouble! Possibly the pilot had turned too sharply at that height and had spun out, or, perhaps he too, suffered from a lack of O2. Whatever the cause, there he was at 20k' with me, spiraling around slowly. I shoved the throttle forward and headed for him, even as he came out of his seeming stupor. the next instant his wing was up and around and the P-39 came at me with all guns blazing. But the Zero was back in its element. I came out of a turn with the Airacobra above and to my right. One quick burst with my cannon and the plane broke in two." ---SAMURAI! Ch.18 p.167-8

v/r
Elf

[Tristanjohn]

Hi Ok thanks, So 10k normal 11k -1, to 19k - 9 And TJ thinks it should start at 14k rather then 11k OK no problem. And the whole issue is the super charger (or lack of one)

(If the ac achived it's fastest speed at 13,800 I'd say being minus below that was incorrect.)

Should not be too hard to fix.

That's not exactly what I wrote, Mogami, or even the essence of it.

The P-39 was a kind of flying misfit--unusual door to the cockpit, tricycle landing gear, engine arranged in the rear, estranged armament, too heavy so a bad climber with the interception of bombers in mind, nowhere near nimble enough to engage the other side's best fighters in anything but passing-fast mode . . . and yet strange as it seems it still proved to be, in its own unique way, a serviceable airplane of sorts. Not great in any one area, mind you, but certainly not all bad and pretty impressive in its own right on the Eastern Front, especially as a tank killer.

The "Zero" had its own issues at altitudes greater than 12,000 feet; had a smallish engine, not turbocharged or for that matter truly "high performance," with little guts at high altitudes; a frame that was light as could be so diving wasn't its game; taking much punishment from enemy fire was a huge no-no; meanwhile its own armament was so-so at best. This plane was, in fact, an early-war very long-ranged fighter escort-type of rig that was on the fragile side and which had its hey-day before the close of 1941 and enjoyed its finest hour at medium and low altitudes against pilots flying inferior aircraft designs who were foolish enough to "dogfight" it, and when Japanese pilots ran out of those types the jig, as they say, was up.

Frankly, if Gary hopes to model any of theese "truths" correctly he's gonna have to break down and come up with a more sophisticated air model. What he has now doesn't make it by half.

Actually, that shouldn't present him with such a large problem. All he needs are a few more modifiers to express the air-combat dynamics in finer detail ("maneuver" and "speed" is a bad joke), experiment with the sequence of combinations, then (the biggie in my view) figure reasonable quantifications for the actual plug-in values.

Also, no more 10,000-foot altitude penalties based willy nilly on someone's "feeling" that that was the way it was. Much better (more responsible) research is called for all around.

[TheElf]

On May 20 we fought the highest air battle in our history, when CDR Nakajima led 15 Zeros into the enemy zone at Moresby at a height of 30,000'. It took us an hour and 20 min. to reach Moresby from Lae. We relied on our height to give us the advantage of suprise, and were astonished to encounter an enemy formation several miles ahead of us at the same altitude.
I was doubtful of the Zero's ability to perform aerobatics at this height. My personal record height witht the Zero was 37,720 feet, acheived with an O2 mask and an electrically heated jacket. At that height the plane was extremely sluggish at the controls, and refused to climb another foot. Consequently, it seemed unwise to fight with the Zero at a height of 30,000'(he isn't saying he would DIVE from 30,000 though )
There were 10 enemy fighters, apparently P-39s of a new design(personally I think they may have been P-40s ). I led the attack and was at once engaged. The 14 other Zeros met the head-on attack of the remaining planes.
The controls were sluggish in the thin air. As the other plane came at me, I tried for an advantageous position from which to fire. We seemed almost to be moving in slow motion. I kept edging clser to the other fighter in a tight spiral, and maneuvered for a quick burst. I yanked the stick over hard--too hard!"

-----At this point Sakai's mask falls off and he blacks out. He doesn't pass out, he blacks out. Not unconciousness, but much like the intial stages of G-LOC when sight is lost. he regains his vision at 20k(keep this altitude in your back pocket)------

"...,I was at 20k, the plane still under control.
I snapped out of the turn instantly, for it was likely that the Airacobra had followed me down and was setting me up for the kill. but the other plane was also in trouble! Possibly the pilot had turned too sharply at that height and had spun out, or, perhaps he too, suffered from a lack of O2. Whatever the cause, there he was at 20k' with me, spiraling around slowly. I shoved the throttle forward and headed for him, even as he came out of his seeming stupor. the next instant his wing was up and around and the P-39 came at me with all guns blazing. But the Zero was back in its element. I came out of a turn with the Airacobra above and to my right. One quick burst with my cannon and the plane broke in two." ---SAMURAI! Ch.18 p.167-8

v/r
Elf

I share this quote for two reasons

1. A few posts ago TJ doubted whether or not Zeros operated at this altitude. Clearly this shows that they did. But I would also submit that it was not the norm given Sakai's comments. Though attacking from this altitude to a lower altitude in the low to mid 20s would seem to be employing the Zero to its fullest given Sakai's comment on the "Element" of the Zero above. Does anyone want to contest that Saburo doesn't know what he's talking about?

2. I think this shows that certainly at 20k' the Zero was "In it's element". Further, if in fact these were P-39s on O2 at 30k' It could also illustrate the Airacobra and its pilots inability to take advantage of a Zero pilot who'd lost his vision at 30,000'. And then was broken in two around 20,000' once the Zero pilot had regained his vision!

As far as modeling EVERY aircraft performance bands at every 1000' interval... I think choosing one aircraft that suffered severely from altitude and modeling that is reasonable.

v/r
Elf

[TheElf]

Also, no more 10,000-foot altitude penalties based willy nilly on someone's "feeling" that that was the way it was.

What makes you think it was willy nilly, or that it was based on "feeling"?

Much better (more responsible) research is called for all around.

The P-39s poor performance at altitude is well-documented. Read my previous posts, particularly from the NASM. I can dig up more if I could just find my issue of Aviation history that covers it exploits

v/r
Elf

[TheElf]

How do I post an image file?

[TheElf]

I asked for and got a little more aircraft data from my buddy at Pax River, it is included alongwith the numbers I previously posted.

Max Level Speed:
A6M2: 282mph@SL 331mph@14,930'
Ki-43II: 272mph@SL 329mph@13,120'
F4F-4: 274mph@SL 320mph@18,800'
P-39D: 309mph@SL 368mph@13,800'
P-40E: 287nph@SL 362mph@15,000'

Best rate of climb:
A6M2: 3150fpm
Ki-43II: 3250fpm
F4F-4: 1950fpm
P-39D: 2550fpm
P-40E: 2100fpm

Power/wt ratio:
A6M2: 5.7lb/hp
Ki-43II: 4.9lb/hp
F4F-4: 6.5lb/hp
P-39D: 5.6lb/hp
P-40E: 6.4lb/hp

Wing Loading:
A6M2: 22lb/sqft
Ki-43II:24.8lb/sqft
F4F-4: 29.9lb/sqft
P-39D: 35.6lb/sqft
P-40E: 31.4lb/sqft

Sustained Turn rate in deg/sec:
1000' 10000' 15000'
A6M2 27 22 20
Ki-43:28 23 19
F4F-4 21 20 17
P-39D 20 16 13
P-40E 20 16 14

Initial Turn rate in deg/sec:
1000' 10000' 15000'
A6M2 40 35 31
Ki-43 40 34 31
F4F-4 33 31 28
P-39D 29 26 23
P-40E 31 27 25

Best turn Radius:
sustained radius sustained turning airspeed
A6M2 339' 110mph
Ki-43 338' 115mph
F4F-4 519' 125mph
P-39D 587' 140mph
P-40E 597' 140mph

Roll Rate in deg/sec:
150mph 200mph 250mph 300mph 350mph 400mph
A6M2 73 61 52 24 17 --
Ki-43 59 63 55 44 21 --
F4F-4 61 67 72 64 49 --
P-39D 63 75 69 59 50 45
P-40E 59 78 100 116 133 75

VNe (never exceed speed):
A6M2: 410mph
Ki-43: 460mph
F4F-4: 480mph
P-39D: 495mph
P-40E: 540mph

Check out these numbers. Particularly the ones for the P-39 and A6M2 at 15k' I think you'll see that the Zero has an edge in turn rate, both instantaneous and sustained, Rate of climb, wing loading, etc. a relative difference in sustained turn rate of 7 degrees per sec is big. P-39 only has an edge in MAX level airspeed. That advatage would be lost as soon as the P-39 strted to turn due to its HUGE disadvantage in wing loading. Unfortunatley we don't know where the numbers that are listed with no altitude occur in the performance charts.

By the way these numbers came from the Navy's TPS (Test Pilot School) in Pax River, MD. They're solid.

v/r
Elf

[TheElf]

The P-39 in Russia. Told you they loved it.

P-39N-1 "Airacobra", 1942 model

The prototype of the P-39 "Airacobra" fighter - XP - 39 (Model 12) was developed by the American Bell Aircraft Corporation in 1938. The fighter was built in such a way as to carry weapons of the largest caliber ever installed on a one-engine aircraft of the time. It was armed with a 37mm T9 cannon - developed by the American Armament Corporation - which fired through the propeller hub, and two synchronized 12.7mm caliber Browning machine-guns installed in the forepart of the fuselage. The engine had to be installed inside the fuselage behind the cockpit to place a gun of this caliber. The air propeller was started with the help of a shaft placed under the cockpit floor.

However, powerful armament availability was not the only concern for the designers working on the new fighter. Along with its fire power, they had to provide for aircraft operation at any time of the day and on ill-prepared runways. With the engine placed behind the cockpit, Bell designed a tricycle landing gear with a steerable nose wheel enabling taxing at high speed, take-off and landing on unprepared surfaces without the risk of the aircraft tipping over. Except for the hydraulic brakes, all XP-39 systems (later P-39) came with an electric drive. The cockpit was very practical and comfortable.

After the trials, the aircraft was completed and launched into large-scale production bearing the name P-39. In the course of production, a great number of modifications were made concerning the armament, engine, air propeller type, fuel reserve and other features. It is worth pointing out that "Airacobra" became increasingly perfected with each new modification.

The N version of the "Airacobra" (P-39N, P-39N-1 and P-39N-5 series) differed from the previous modifications in terms of improved flight performance due to a reduced fuel reserve (325 l) and weaker armor protection. This version of the P-39 saw the introduction of the new Allison V-1710-85 engine (power 1,200 HP) and Aero Prop propeller. The aircraft's armament consisted of a 37mm T9 cannon, two 12.7mm machine guns in the nose and four wing-mounted 7.62mm Browning machine guns. Overall, 2,095 aircraft of this variation were produced.

The Airacobra was shipped to the USSR under the lend-lease program. Altogether, the Soviet Union received approximately 4,750 P-39 aircraft of D, N and Q variations.

Good flight performance at low altitudes allowed the Airacobra to be used effectively for escorting Il-2 attack planes and protecting them from enemy fighters, bomber intercepts as well as ground attack. Contrary to popular belief, Soviet Union never used P-39s in ground attack role.