P-39

[EvilDingo]

I would love to see this plane in AH. It's performance wouldn't break any records, but it certainly wouldn't be a hangar queen. Great guns, great look, and distinct flight characteristics that would make it unique to fly.

Does anyone have any performance specs for the various models? I know it had serious issues with stalls and spins and could be quite unstable. Even so, almost 10,000 were manufactured, close to half of those going to the Soviet Union.

Thoughts?

[EvilDingo]

Woops, forgot the pretty picture.

[DblTrubl]

I've been itching to fly this bird too. I was hoping a P-39D would be included in 1.10. A VVS P-63 would also be a nice addition and perhaps a bit more competitive in the MA.

Specs below are from Joe Baugher's website.
Specification of Bell P-39D Airacobra:

Engine: One 1150 hp Allison V-1710-35 twelve-cylinder liquid cooled engine. Performance: Maximum speed 309 mph at sea level, 335 mph at 5000 feet, 355 mph at 10,000 feet, 368 mph at 12,000 feet, and 360 mph at 15,000 feet. An altitude of 5000 feet could be reached in 1.9 minutes. It took 5.7 minutes to reach an altitude of 15,000 feet and 9.1 minutes to reach 20,000 feet. Service ceiling was 32,100 feet. Maximum range (clean) was 600 miles at 10,000 feet at 231 mph. Range with one 145.7 Imp gal drop tank was 1100 miles at 196 mph. Weights: 5462 pounds empty, 7500 pounds gross, and 8200 pounds maximum takeoff. Dimensions: Wingspan 34 feet 0 inches, length 30 feet 2 inches, height 11 feet 10 inches, and wing area 213 square feet. Armament: One 37-mm cannon in the nose with 30 rounds. Four wing-mounted 0.30-inch machine guns with 1000 rpg, two fuselage-mounted 0.50-inch machine guns with 200 rounds per gun. One 250 lb, 325-lb, or 500-lb bomb could be carried underneath the fuselage.

Specification of P-63A-10:

Engine: One Allison V-1710-93 twelve-cylinder Vee liquid cooled engine with a single-stage supercharger and auxiliary hydraulic turbosupercharger, rated at 1325 hp at sea level and 1150 hp at 22,400 feet. Performance: Maximum speed was 361 mph at 5000 feet, 392 mph at 15,000 feet, and 410 mph at 25,000 feet. An altitude of 25,000 feet could be reached in 7.3 minutes. Service ceiling was 43,000 feet. Ferry range was 2575 miles. Weights were 6375 pounds empty, 8800 pounds loaded, and 10,500 pounds maximum takeoff. Dimensions: Wingspan 38 feet 4 inches, length 32 feet 8 inches, height 12 feet 7 inches, and wing area 248 square feet. Armament One 37-mm M10 cannon with 58 rounds firing through the propeller hub, two 0.50-inch machine guns in the nose with 200 rpg, and one 0.50-inch machine gun in each of two underwing gondolas with 200 rpg. A centerline underfuselage rack could carry a 75-US gallon auxiliary fuel tank or a 500-lb bomb.

[Tony Williams]

The mixed armament was a bit of a problem. The .30" had a reasonably high muzzle velocity but lost it and dropped away fast. The .50" kept on going. The 37mm had a low velocity so didn't match the others at all. Not easy to hit with all of them at once, unless you were very close.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

[whgates3]

according to my book, USSR got 5707 P-39s, RNZAF got a bunch (P-400s w/ 20mm instead of 37mm in the nose) & the USAAF used it in the Aleutians, Soloman Islands, New Guinea & North Africa. So, other than CBI, the P-39 was in all theaters of the war. Other than the P-40 no fighter was used more widely...

[Pei]

The 37mm had a low velocity so didn't match the others at all. Not easy to hit with all of them at once

I rather suspect that if you got close enough to attempt a hit with the 37mm you wouldn't need to bother with the MGs .

Here's an interesting question:
Did the Soviet P-39s get fitted with the NS-37 (or some other Soviet cannon), or were they using the original US armament?

[HoHun]

Hi Tony,

>The mixed armament was a bit of a problem. The .30" had a reasonably high muzzle velocity but lost it and dropped away fast. The .50" kept on going. The 37mm had a low velocity so didn't match the others at all. Not easy to hit with all of them at once, unless you were very close.

Do you have an actual set of trajectory diagrams for the P-39? It's my impression that for the relatively short ranges typical for air combat, trajectory differences usually could be compensated for with good accuracy by selecting different elevation values for each set of guns. The impact points would finally diverge vertically, but too far downrange to matter in air combat.

(The wing-mounted guns were diverging worse, anyway, for purely geometric reasons.)

Regards,

Henning (HoHun)

[Tony Williams]

Originally posted by Pei

Here's an interesting question:
Did the Soviet P-39s get fitted with the NS-37 (or some other Soviet cannon), or were they using the original US armament?

They stuck with the US guns. I've often wondered why - the NS-37 was in a different league in terms of both muzzle velocity and rate of fire, but the problem might have been weight; about 70% more.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

[Tony Williams]

Originally posted by HoHun
Hi Tony,

Do you have an actual set of trajectory diagrams for the P-39? It's my impression that for the relatively short ranges typical for air combat, trajectory differences usually could be compensated for with good accuracy by selecting different elevation values for each set of guns. The impact points would finally diverge vertically, but too far downrange to matter in air combat.

(The wing-mounted guns were diverging worse, anyway, for purely geometric reasons.)

Regards,

Henning (HoHun)

Hi Henning.

No, I have no trajectory diagrams. The only data I have is for projectile drop at a couple of ranges: at 365m, the 37mm dropped 137cm (.50 = 81 cm) while at 730m the drop was 1,440cm (.50 = 867cm).

Of course, that was only part of the problem. The flight time of the big shells was much longer than that of the .50" bullets, so even if the guns were harmonised to strike at the same point, if the .50s were hitting the 37mm might arrive too late - except in a straight tail chase.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

[Karnak]

I've always thought of the P-39D as the pre-Dreadnought of WWII fighters.

Armed with a bevy of mismatched weapons that don't support each other.

[HoHun]

Hi Tony,

>The only data I have is for projectile drop at a couple of ranges: at 365m, the 37mm dropped 137cm (.50 = 81 cm) while at 730m the drop was 1,440cm (.50 = 867cm).

Now think about the adjustment possiblities: For example, by making the the trajectories cross at 365 m, you'd have both projectiles strike very near the aiming point (within 50 cm) from point blank range out to at least 500 m, which in a WW2 context is pretty much maximum effective range anyhow.

>Of course, that was only part of the problem. The flight time of the big shells was much longer than that of the .50" bullets, so even if the guns were harmonised to strike at the same point, if the .50s were hitting the 37mm might arrive too late - except in a straight tail chase.

The flight time difference becomes a problem only with long flight times - and that means with long range. However, at long range, the only viable target is a non-manoeuvering one anyhow, so I don't think flight time difference is really a limiting factor.

Regards,

Henning (HoHun)

[Samm]

When you're firing the 37mm do you really need to supplement it with mg's ?

 Unlike the flakyak the mgs on the p63 would actually be usefull as "rtb" guns .

[EvilDingo]

The principal difference between the P-39Q and earlier version was in the fighter's armament--the four wing-mounted 0.30-inch machine guns were replaced by a single 0.50-inch machine gun mounted in a fairing underneath each wing. The ammunition capacity of the underwing guns was 300 rounds per gun. The two fuselage-mounted 0.50-inch machine guns with 200 rpg, plus the hub-mounted 37-mm cannon with 30 rounds, were retained. The replacement of the four wing guns was generally applauded by American pilots, most of whom thought that the 0-30-inch guns of the earlier versions were too light to be effective and it wasn't worth the extra fuel needed to carry the 4000 rounds of 0.30-inch ammunition. However, the Russians, who got most of the P-39Qs built, usually had the underwing gun pods removed.

So starting with the P-39Q, the armament differences were pretty much null and void anyway. 4 .50s, and one whopper 37mm. Also, this was the most widely produced version. From what I've read, at low alts the P-39 really shined which is probably why the Russians liked it so much.

[Sachs]

I've heard the russians were afraid of heights.

[Seeker]

One of the NG's I lurk in is lucky enough to have a Vet or two post there.

I thought this might be of interest.........


What Hugh Dow said about the P-39 armament.
............................. ............................. .

Armament loads for the P-39 D through M models:

30 cannon rounds, 200 rounds in each of the two nose 50s (I
could never remember whether it was 200 or 250 rounds) and
1000 in each of the four wing 30s.  I think that these are
correct, though we never carried that many rounds in the
wing guns except on strafing missions.  They also say that
the Q model carried 300 rounds for each of the two 50
caliber wing pods and that the pilots thought that this was
a great improvement over the 30s.  I'm sure they never
spoke to anyone who ever flew the two birds in combat.  It
was a BIG step backwards as far as I was concerned -- cut
down its quick roll rate and slowed the bird down so that
we could never have caught an enemy a/c in a chase.  And
though we never flew any strafing missions in the Q, that
I know of, the two wing mounted 50s would have shot their
wad about the same time as the nose mounted synchronized
guns, leaving the bird with an entirely too limited firing
time for many strafing ops.  I would have never shot down
my second Me-109 if I had been flying a Q--there would have
had no ammo to fire by the time I encountered him and I
might not have been able to out turn him with those awful
pods hanging out there. There is an interesting comparison
of the P-39 against the ME 109 E and the Spitfire VB,
reportedly conducted by the RAF test unit at Duxford in 41
or 42 where they found that the Airacobra could out turn
and out run the 109 below about 15,000 and could out run
and out dive the Spit at these lower altitudes.  Of course,
both the Spit and the 109 could outclimb the 39 and the Spit
could also out turn the Airacobra at these lower altitudes,
as well as all higher altitudes.  This is the first
independent verification I have ever seen of what I have
said over the years about our comparative trials at Elmas,
Sardinia between the Me-109 and the P-39.  Naturally, I'll
be able to use some of this data when I get back to the
paper, "P-39 Airacobra in Combat".

 Rowdy