P39-L1 Kobra performance and discussion

[Trooper117]

Mate, have you actually spent time reading about the history of this aircraft? 

'The spin was a known killer'' if the pilot didn't follow the recovery procedure to he was likely to die... that procedure is very different to other standard WWII aircraft.

The position of the engine behind the pilot altered the COG... with the correct training, it was of course recoverable, but don't be deceived, it will catch many out in the next theatre.

Edited September 9, 2016 by Trooper117

[=362nd_FS=Hiromachi]

The major problem I find here is maneuverability. It's capable fighter and can turn very well as Manu linked, but at the same time as indicated in NACA reports its unstable at higher angles of attack and there is lack of stall warning (as it sounds a complete lack), so one trying to turn very tight may find it hard turning at those high angles of attack. Riding on the edge of stall might be a no go here. 

[YSoMadTovarisch]

The P39D in Manu's chart was armed with a 20mm cannon, if we're to get the 37mm cannon version it shouldn't turn nowhere near as well, iirc the P39Q with 1 x 37mm and 2 x 50 cal in Soviet test had a turn time of 20s, slightly better than the G2, but not enough to make a difference considered the nasty stall characteristic and the 109's much better at riding the stall.

[II./JG77_Manu*]

The P39D in Manu's chart was armed with a 20mm cannon, if we're to get the 37mm cannon version it shouldn't turn nowhere near as well, iirc the P39Q with 1 x 37mm and 2 x 50 cal in Soviet test had a turn time of 20s, slightly better than the G2, but not enough to make a difference considered the nasty stall characteristic and the 109's much better at riding the stall.

you care to elaborate why the change of cannon would make such a huge difference?

[YSoMadTovarisch]

you care to elaborate why the change of cannon would make such a huge difference?

 

Plus I read a P39K US test and it had a stall speed of 105mph IAS, which is quite a bit higher than the 109G.

http://www.wwiiaircraftperformance.org/P-39/P-39K-1_L1_Operating_Instructions.pdf

Page 22:

 

The airplane has good stalling characteristic (about 105 mph "Flaps up" and about 90 mph "Flaps down")

Edited September 9, 2016 by GrapeJam

[II./JG77_Manu*]

 

Plus I read a P39K US test and it had a stall speed of 105mph IAS, which is quite a bit higher than the 109G.

 

Well well, but the K/L series are way closer to the D, then the Q-15. 

[JtD]

Test data was 15 minute rating, i am aware that 5-min rating will make this a little better.

Regarding turning, i have some data in an old post here..the P39 (when the turning of the L can be compared to the D, what i'd expect) should turn nearly as good as the Spit Mk9, some good 1,5s better then the Yak1b, so definitely able to outturn everything the Germans have with ease.

~18s for an aircraft with 17% higher weight, 12% lower power, 11% higher span loading and 5% lower wing loading when compared to a Bf109G, which is at ~21s. Not supported if using the same physics.

[II./JG77_Manu*]

~18s for an aircraft with 17% higher weight, 12% lower power, 11% higher span loading and 5% lower wing loading when compared to a Bf109G, which is at ~21s. Not supported if using the same physics.

P40© is even less powerful with pretty similar weight, and Bf109F (19s turn time) pilots have been told to never engage a horizontal turnfight with them. There's surely a lot more to turn rate, then the 4 figures you were just giving

If i had to guess, i'd say the weight distribution within the aircraft also can make quite a difference

Edited September 9, 2016 by II./JG77_Manu*

[JtD]

Sure, and the "a lot more to turn rate" also doesn't support these figures. Neither does it support the 18s for the P-40.

[A_radek]

turn rate..    what interests me more is the effect (or lack of) of that clean low-drag airframe.

And truly hope it will come with different weapon field modifications. 1x37 and and 2x 50's will be plenty. I'd even sacrifice some armor for a few less kilos.

[Willy__]

 

 

The major problem I find here is maneuverability. It's capable fighter and can turn very well as Manu linked, but at the same time as indicated in NACA reports its unstable at higher angles of attack and there is lack of stall warning (as it sounds a complete lack), so one trying to turn very tight may find it hard turning at those high angles of attack. Riding on the edge of stall might be a no go here. 

 

That sounds like an aircraft we have in game right now....   

[=WH=PangolinWranglin]

Would anyone happen to know how to recover from a stall? I am very excited and don't want to make a fool of myself. 

[Trooper117]

Sorry, I meant spin recovery, not stall... I used to know it by heart but will check in my manual for you tomorrow.

If I remember right it has two phases, a pre recovery, followed by the recovery... and I do remember that if it was not done swiftly enough, the aircraft would not recover.

[Matt]

This manual might be useful.

 

http://www.wwiiaircraftperformance.org/P-39/P-39K-1_L1_Operating_Instructions.pdf

Just check page 19 of the manual.

[LittleJP]

Not very well versed on the Aircobra at all. Armament wise, did it serve as 2x .50 cal and 20 mm cannon, or was it limited to 2x .50 with the 37mm, with optional 4x .303s?

[ShamrockOneFive]

Not very well versed on the Aircobra at all. Armament wise, did it serve as 2x .50 cal and 20 mm cannon, or was it limited to 2x .50 with the 37mm, with optional 4x .303s?

 

Most P-39s had a 37mm M4 cannon firing through the propeller hub and Browning M2 .50cals in the nose. Most also had four Browning .30cal machine guns in the wings. Later on in the Q models the .30cal machine guns were removed and small .50cal pods were fitted to the wings. These gunpods were frequently removed by Russian crews leaving the aircraft with just the nose mounted .50cals and 37mm.

 

Early models of the P-39 had a US licensed version of the Hispano 20mm cannon installed instead of the 37mm cannon. These were the P-400 (export versions) and P-39D-1 batches mostly but it gets a little confusing from there

[LittleJP]

Alright. Did the ones serving on the Russian side have 20 mms mounted? Be curious in what kind of different loadouts we can expect. I for one would probably stick find a 20mm and .50s perfectly adequate, if it's historical.

 

A slow firing 37 mm is all fine and dandy, but the lack of ammo really would be troublesome.

[ShamrockOneFive]

Alright. Did the ones serving on the Russian side have 20 mms mounted? Be curious in what kind of different loadouts we can expect. I for one would probably stick find a 20mm and .50s perfectly adequate, if it's historical.

 

A slow firing 37 mm is all fine and dandy, but the lack of ammo really would be troublesome.

 

The Russians did have some of the Airacobra Mark I/P-400 models that the British rejected in service and these were armed with the 20mm cannon. The P-39L-1 version that we have traces back to the P-39D-2 which was armed with the 37mm cannon (the original armament BTW) so its very likely that we'll have the 37mm cannon (with 30 rounds) fitted. The Hispano only had a drum feed and that had a maximum of 60 rounds so it the cannon didn't carry very much ammunition at all.

Edited September 10, 2016 by ShamrockOneFive

[CF-105]

Yep, turnfight-wise it will probably beat everything apart the I16...however i fear it will really lack climb rate. According to the data Matt provided, at 60% fuel the climb rate is comparable to the Lagg3 (with 100%). 

 

My issue with the Lagg-3 isn't it's climb rate, speed, or engine power, it's just its turn rate/stall speed.

The P-39 will be wonderful for me.

[Holtzauge]

I’m also looking forward to trying out the P-39: It’s such an unusual design and it will certainly be fun to try out the 37 mm..…  

 

Americas hundred thousand by F. H. Dean is as mentioned before a good source of data. There is a figure  21 on page 191 which gives the following data for P-39 D, D-1, D-2, F and K-1 at military power:

 

Weight for performance numbers given for 7631 lb (3464 Kg)

 

Max speed ca 370 mph at 12,000 ft ( 595 Km/h at 3658 m) and ca 310 mph (499 Km/h) at SL.

 

Climb rate ca 2400-2500 fpm up to 12,000 ft (12.2-12.7 m/s up to 3658 m)

 

Climb time up to 16,400 ft (5000 m) just over 7 min

 

(Read off up to 5 Km because it can then be compared to the IIRC correct 5 min for Fw-190 and Yak-1)

 

Now these figures are for military power Allison V-1710-63, which is given as 1150 hp at 3000 rpm 42”” but there is also WEP for the D-2 which is given as 1590 hp at 2500 ft with 3000 rpm and 61””. However, there are no performance figures given at WEP in Dean’s book.

 

Disclaimer: I only eyeballed the above numbers from the chart so they may be somewhat off but they give you an idea anyway.

 

So while it certainly packs a punch with the 37 mm, it is not such a stellar performer in speed and climb. Will consequently have to be flown with care if mixing it up with Fw-190’s and Me-109’s……

[Sokol1]

[Venturi]

Americas hundred thousand by F. H. Dean is as mentioned before a good source of data. There is a figure  21 on page 191 which gives the following data for P-39 D, D-1, D-2, F and K-1 at military power:

 

Weight for performance numbers given for 7631 lb (3464 Kg)

 

Max speed ca 370 mph at 12,000 ft ( 595 Km/h at 3658 m) and ca 310 mph (499 Km/h) at SL.

 

Climb rate ca 2400-2500 fpm up to 12,000 ft (12.2-12.7 m/s up to 3658 m)

 

Climb time up to 16,400 ft (5000 m) just over 7 min

 

(Read off up to 5 Km because it can then be compared to the IIRC correct 5 min for Fw-190 and Yak-1)

 

Now these figures are for military power Allison V-1710-63, which is given as 1150 hp at 3000 rpm 42”” but there is also WEP for the D-2 which is given as 1590 hp at 2500 ft with 3000 rpm and 61””. However, there are no performance figures given at WEP in Dean’s book.

 

 

From Vees for Victory pg 434

 

[VBF-12_Snake9]

Will the 37mm be anything like the 37 on the lagg?

 

I ask because the lagg 37 rate of fire is so bad the gun is only useful against slow moving bombers.

[Venturi]

(p39) m4 37mm cannon, 150rpm, 2000ft/sec muzzle veloc, 608g HE-T, 750g AP-T

 

(lagg 3) sh37 37mm cannon, 175rpm, 2950ft/sec muzzle veloc, 735g HEI or 760g AP-T ----- cannon was experimental use only on lagg 3

Edited September 11, 2016 by Venturi

[MiloMorai]

The U.S did not supply M80 armor-piercing rounds for these lend-Lease aircraft, instead, the Soviets received 1,232,991 M54 high-explosive rounds. The M4 was sometimes used against soft ground targets but was primarily for air-to-air combat on the Eastern Front at which duty it was highly effective. The Soviets did not use the P-39 for tank-busting. Soviet pilots appreciated the M4's reliability but complained of its low rate of fire (three rounds per second) and small magazine size (30 rounds).

[216th_Jordan]

Will the 37mm be anything like the 37 on the lagg?

 

I ask because the lagg 37 rate of fire is so bad the gun is only useful against slow moving bombers.

 

I think its actually quite good. M4 gun is a lot slower.  Definately not a snapshot weapon.

[VBF-12_Snake9]

(p39) m4 37mm cannon, 150rpm, 2000ft/sec muzzle veloc, 608g HE-T, 750g AP-T

 

(lagg 3) sh37 37mm cannon, 175rpm, 2950ft/sec muzzle veloc, 735g HEI or 760g AP-T ----- cannon was experimental use only on lagg 3

If I understand this. The lagg 37 has a greater rate of fire than the p39 does.

 

Wow that sucks for the 39.

[=362nd_FS=Hiromachi]

I'd throw that 37 mm away and stuck in there Hispano, even though pilots complained about magazine with only 60 rounds it still sounds like a better option for dogfights. Even hunting bombers with that 37 mm wont be easy, unless one hangs on bomber tail ...

[seafireliv]

Some good ole American nose art. This better be a in-game, not a custom skin.

 

 

With Feminism in today`s world screwing everything up, even games and sims, don`t bet on it.

[Venturi]

To put it in perspective, that is 2.5 rounds per second. M4 muzzle velocity is just two hundred ft/sec slower than the mg151/20. 

 

Not good for high deflection shots but fine for shots from astern. 

 

https://www.youtube.com/watch?v=t-JOTgBwQgY

Edited September 11, 2016 by Venturi

[ShamrockOneFive]

I always used it as more of a sniper in the IL-2 1946 aircraft. You come in with your .50cals and .30cals going and when the timing seems right... tap the cannon and put a single round towards the target at fairly close range. One or two hits is usually all that you needed.

 

It's not that different with the LaGG-3's Sh37.

[SOLIDKREATE]

The P-39 is a phenomenal plane.....as long as you don't turn LOL!

[216th_Jordan]

I always loved the 37mm in the old Il-2. I do find the soviet 37mm a bit underwhelming though. It was said that the M4 could take down a bomber in 1 or 2 shots, with the soviet 37mm you definately need more.

[707shap_Srbin]

With Feminism in today`s world screwing everything up, even games and sims, don`t bet on it.

 

Well, soviets also had girls in mind.

 

Красотулечка - Bell Beauty

[216th_Lucas_From_Hell]

There were a few P-39s delivered through Iran which still packed 20mm cannons, but they were exceptions rather than the rule. If memory serves me right there were about seven of them between 16 GIAP and 45 IAP, including Ivan Babak's first P-39. Those were of P-39D production though, so not applicable to the P-39L-1 we are getting

[-=PHX=-SuperEtendard]

Maybe there will be 20mm as a mod... because currently there are mods that "shouldn't be there"? like the gunpods for the Mc 202, or the several gun variants of the MiG-3, or the 37mm for the IL-2 mod 42?

Edited September 11, 2016 by -=PLR=-SuperEtendard

[LukeFF]

 

 

the several gun variants of the MiG-3, or the 37mm for the IL-2 mod 42?

 

Those are perfectly valid loadouts that were used operationally.  

[-=PHX=-SuperEtendard]

Those are perfectly valid loadouts that were used operationally.  

But I meant is as if they were for specific variants which aren't strictly the ones modelled in the game right now? (like if giving a 30mm for a G2 for example)

[216th_Lucas_From_Hell]

The MiG-3 we have (late version) packed all the armament you have there, AFAIK all at more than 200 units each.

 

The P-39 will probably offer additional armour or its removal, particularly cockpit armour.

[JtD]

We have a MiG-3 series 24, no more than 100 of which were produced. You don't put 'more than 200' of several different weapon layouts into 100 planes - which I think is the point SuperEntendard is making. In general, the armament options for the aircraft are a little bit generous. Which is why I'd expect the 20mm gun in the P-39L as an option, even though the manual only lists the 37mm gun.