P39-L1 Kobra performance and discussion

[II./JG77_Manu*]

Very excited to see this new plane coming to BoX. My favourite inline prop fighter of all time

 

Unfortunately i only have performance sheets about P39-D and P39-Q/N family, and next to no idea about the performance from K/L.

Does anyone here have some data? Would be really interested, and how it compares to the other best (coming) Soviet fighters Yak1b and Yak7b. 

Especially about engine limits, and if they are as rigid as the ones of the P40-E.

Thanks in advance

 

I will mostly fly it regardless at least against the hs129 it will prove more then deadly 

Edited September 8, 2016 by II./JG77_Manu*

[Trooper117]

I think the Soviets received more Q and N versions overall didn't they?

[Matt]

This manual might be useful.

 

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

 

[II./JG77_Manu*]

Thanks Matt.

 

15 minutes at 3000rpm. Thank god

[BlitzPig_EL]

V-1710-63 rated at 1325 hp.

[BlitzPig_EL]

Thanks Matt.

 

15 minutes at 3000rpm. Thank god

 

Also 5 minutes at 3000rpm/51 inches for take off, which gives the 1325bhp I mentioned.

Edited September 8, 2016 by BlitzPig_EL

[=362nd_FS=Hiromachi]

I only have some flight trials, comparing P-39 Q with A6M3 "Hamp" if you are interested. 

[II./JG77_Manu*]

I only have some flight trials, comparing P-39 Q with A6M3 "Hamp" if you are interested. 

Sure, why not post them here, so everyone can see them this topic should be about the plane itself, and gather information

[=362nd_FS=Hiromachi]

It's more about what Hamp can and cant do, or what Airacobra pilot should do and what should avoid. But there are some details on acceleration for instance. Also, keep in mind that Hamp in this test was not operated at proper settings and performed quite a bit below original specification:

 

 

 

 

 

I will later look into my library to see if I can find more on P-39. L is somewhat mysterious to me, most of the time you hear about P-39 D/P-400 or P-39 N and Q. 

[II./JG77_Manu*]

Thanks mate.

 

 

 

I will later look into my library to see if I can find more on P-39. L is somewhat mysterious to me, most of the time you hear about P-39 D/P-400 or P-39 N and Q. 

 

 

Yep, same here. That's the reason i was asking, next to no knowledge to K/L series in contrary to earlier and late Kobra.

[[CPT]Pike*HarryM]

I have a book ( http://tinyurl.com/jprf38a )  that says this about the P-39L:

 

 

The P-39L followed (after the K), of which 250 were built using serial numbers 42-4454 through 42-4703. The P-39L added a streamlined low drag nosewheel. It could be fitted with wing rails to launch rockets in combat. The P-39L returned to the Curtiss Electric propeller. It had improved low altitude performance. It was otherwise identical to the P-39D-2. P-39Ls flew in New Guinea and North Africa in 1943. P-39L-2s were eleven P-39Ls modified for photo-reconnaissance.

[JtD]

It's basically a P-39D-2 with a different propeller. You can expect it to at low altitude fly circles around every plane we currently have in game while being as fast as the Fw190A-5. 250 were built.

[-TBC-AeroAce]

P39 is a very interesting design! I wonder how good it could have been with some development and if the jet was a bit later!

 

Remember all our favs like the Spit or 109 started out quite poor

Edited September 8, 2016 by AeroAce

[BlitzPig_EL]

I am looking forward to flying it in this game engine.

 

Getting a handle on the 37mm's ballistics will be a challenge, as it is far different from the machine guns on the aircraft, but I did it back in the old days, and it was effective.  The 39 was the first aircraft in IL2/46 that I got good at flying and fighting with.

 

The L is an interesting variation.  Not one you ever hear much about.

[=362nd_FS=Hiromachi]

I'm not sure about its combat capability but if this helps, the following document is a "Bible" of flight characteristics and flying qualities (I uploaded it to my google disk, if something doesnt work than please say so) :

https://drive.google.com/file/d/0B0Iwvrpz0e6CVW85dE9OUlJpN0U/view

A flight investigation of the flying qualities of a standard Bell P-39D-1 airplane was made by the NACA at Langley Field, Va. The tests were conducted during February and March of 1943 and consisted of 21 flights requiring a total flying time of approximately 23 hours. The present report is a summary covering all data obtained in the flying-qualities investigation. Of course there are differences to some degree (engine, power ratings, armament) but airframe is same which makes it probably best to determine what can be expected of it in flight.

[Y29.Layin_Scunion]

Did the "L" variant have nose mounted .50 cals refitted like most other Soviet Cobras?  

[BlitzPig_EL]

Did the "L" variant have nose mounted .50 cals refitted like most other Soviet Cobras?  

 

What do you mean, "refitted"?   

 

Like all P 39s in addition to the nose cannon, there were two .50" Brownings synchronized to fire through the propeller disc. 

[JtD]

The L armament is 1x37mm+2x0.50 in the nose and 4x0.30 in the wings. 30 rounds for the 37mm gun were carried, 200rpg for the 0.50 and 300rpg for the 0.30.

Edited September 8, 2016 by JtD

[Y29.Layin_Scunion]

What do you mean, "refitted"?   

 

Like all P 39s in addition to the nose cannon, there were two .50" Brownings synchronized to fire through the propeller disc. 

I apologize, I'm thinking of them simply removing the wing mounted .30 cals, which a lot of Soviets did.  The 50s were always in the nose.  Just curious to the armament which JtD answered specifically.

Edited September 8, 2016 by Y-29.Layin_Scunion

[Trooper117]

Getting the spin recovery right will be very interesting... this will catch a lot of flyers out, be sure...

[II./JG77_Manu*]

It's basically a P-39D-2 with a different propeller. You can expect it to at low altitude fly circles around every plane we currently have in game while being as fast as the Fw190A-5. 250 were built.

 

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%). 

[Y29.Layin_Scunion]

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%).

 

Eh...LaGG isn't terrible but it's not great either. I see what you're saying though. Compared to a G-4, it'll be tough.

[II./JG77_Manu*]

Eh...LaGG isn't terrible but it's not great either. I see what you're saying though. Compared to a G-4, it'll be tough.

 

That's exactly what i wanted to say yes. Not terrible, like the P40 (god forbid), but also not rapid like the Yaks. Anyway, much looking forward to it  

[Turban]

Getting the spin recovery right will be very interesting... this will catch a lot of flyers out, be sure...

 

 

The outrage will be something like we haven't seen before, as that spin was very nasty. 

[69th_chuter]

The outrage will be something like we haven't seen before, as that spin was very nasty. 

 

 

Only when the ammo was gone.  The spin characteristics were variable dependent on CG, but the game may pick one universal characteristic as has been done in previous games.  We'll see.

[Rjel]

Time to watch some of the training films for the P-39 on YouTube. Honestly when I read the announcement at work today, I thought the P-39L designation was a mistake. Never heard of that model before. 

[ShamrockOneFive]

I apologize, I'm thinking of them simply removing the wing mounted .30 cals, which a lot of Soviets did.  The 50s were always in the nose.  Just curious to the armament which JtD answered specifically.

 

Interestingly, this page talks about the removal of the .50cal gunpods fitted in later versions but pointed out that in many photos, the .30cals are still present.

http://mig3.sovietwarplanes.com/lendlease/p-39/misos/general.html

 

So that comment about removing guns may have been mostly about the pods rather than the wing mounted weapons. I'm curious if others have details on removal. They certainly kept the .50cals in the nose and from what I hear, the 37mm was very well liked.

 

 

Only when the ammo was gone.  The spin characteristics were variable dependent on CG, but the game may pick one universal characteristic as has been done in previous games.  We'll see.

 

Weight definitely changes when ammo is removed... it'll be interesting to see if the engine also removes the weight positionally or from the fixed overall weight of the aircraft. A question for the flight model programmers!

[69th_chuter]

I have a book ( http://tinyurl.com/jprf38a )  that says this about the P-39L:

 

 

The late-style "low drag" nose wheel is a larger diameter wheel/low profile tire (same circumference) with a higher pressure.  I believe the "lower drag" is actually a reference to ground roll not aerodynamics but almost every author that references it seems to imply aerodynamics.  And, like all other nose wheels on combat aircraft in WW2 it's non-steerable (castoring).  It will be interesting to see how P-39 taxiing is modeled (1946 modeled all nosewheels as steerable).

[Fern]

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

 

[Fern]

Getting the spin recovery right will be very interesting... this will catch a lot of flyers out, be sure...

 

The outrage will be something like we haven't seen before, as that spin was very nasty. 

 

And this is how shit starts in these forums.

 

Read this below: http://www.warbirdsresourcegroup.org/URG/p39_design.html

 

The weight distribution of the P-39 was supposedly the reason for its tendency to enter a dangerous flat spin, a characteristic Soviet test pilots were able to demonstrate to the sceptical manufacturer who had been unable to reproduce the effect. After extensive tests, it was determined the spin could only be induced if the aircraft was improperly loaded, with no ammunition in the front compartment. The flight manual noted a need to ballast the front ammunition compartment with the appropriate weight of shell casings to achieve a reasonable center of gravity. High speed controls were light, consequently, high speed turns and pull-outs were possible. The P-39 had to be held in a dive since it tended to level out, reminiscent of the Spitfire. Recommended dive speed limit (Vne) was 475 mph (764 km/h) for the P-39.

Soon after entering service, pilots began to report that “during flights of the P-39 in certain maneuvers, it tumbled end over end.” Most of these events happened after the aircraft was stalled in a nose high attitude with considerable power applied. Concerned, Bell initiated a test program. Bell pilots made 86 separate efforts to reproduce the reported tumbling characteristics. In no case were they able to tumble the aircraft. In his autobiography veteran test and airshow pilot R.A. “Bob” Hoover provides an account of tumbling a P-39. He goes on to say that in hindsight, he was actually performing a Lomcevak, a now common airshow maneuver, which he was also able to do in a Curtiss P-40. An informal study of the P-39’s spinning characteristics was conducted in the NASA Langley Research Center 20-foot Free-Spinning Tunnel during the 1970s. A study of old reports showed that during earlier spin testing in the facility, the aircraft had never tumbled. However, it was noted that all testing had been done with a simulated full ammunition load, which drew the aircraft’s center of gravity forward. After finding the original spin test model of the P-39 in storage, the new study first replicated the earlier testing, with consistent results. Then, the model was re-ballasted to simulate a condition of no ammunition load, which moved the aircraft’s center of gravity aft. Under these conditions, the model was found to often tumble when thrown into the tunnel.

Edited September 9, 2016 by Fern

[Willy__]

Keep your ammo and never shoot and you will be fine. LW pilots thanks you.   

 

   

[JtD]

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%).

You're forgetting that the test data is usually for the military rating, but a emergency rating was also available. This will boost the climb rate to somewhere between 16m/s and 20m/s. In terms of turning, it should be somewhere near a low fuel P-40E, given it has a smaller wing and is about the fuel load lighter. The P-39's reputation in the VVS however was much better than the P-40's, and seeing how poorly the P-40 performs in game (matching the reputation), I'm expecting miracles from the P-39 (matching the reputation), just like it was in Il-2:1946.

 

If the current Fw190 was a reference, both the Spitfire and the P-39 would simply be unflyable owing to control issues. But again, don't worry, it will be fine.

 

You guys been here?

http://www.wwiiaircraftperformance.org/P-39/P-39.html

Not much on the L, but still good for a general picture.

[LLv34_Wmaker]

Per Francis H. Dean's America's Hundred Thousand, P-39L's Allison-63 had a 61" WEP setting with an output of 1590hp for 5 minutes which is the highest power output for production Airacobra. Not sure weather that power setting was available to the Soviets during the Battle of Kuban. It is known that Stalin himself made sure that Pokryshkin's 9 GIAD got all the 100 octane fuel they needed for their P-39s during Operation Bagration.

 

Of the 4719 - 4942 Airacobras recieved by the USSR, 137 were L-models.

[II./JG77_Manu*]

You're forgetting that the test data is usually for the military rating, but a emergency rating was also available. This will boost the climb rate to somewhere between 16m/s and 20m/s. In terms of turning, it should be somewhere near a low fuel P-40E, given it has a smaller wing and is about the fuel load lighter. The P-39's reputation in the VVS however was much better than the P-40's, and seeing how poorly the P-40 performs in game (matching the reputation), I'm expecting miracles from the P-39 (matching the reputation), just like it was in Il-2:1946.

 

If the current Fw190 was a reference, both the Spitfire and the P-39 would simply be unflyable owing to control issues. But again, don't worry, it will be fine.

 

You guys been here?

http://www.wwiiaircraftperformance.org/P-39/P-39.html

Not much on the L, but still good for a general picture.

 

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. 

[=362nd_FS=Hiromachi]

America's Hundred Thousand is a good source, that section in which this MAP is mentioned should be send to developers.

 

Anyway, I expect it also hard aircraft to control in maneuvering near maximum angle of attack, as in provided NACA document:

"In every 'condition tested, the stall developed abruptly, There was no warning of the approaching stall either in the form of buffeting and shaking of the airplane or controls, or in the form of a marked Increase in the rearward movement of or force on the control stick. At the stall break, the ailerons floated in such a manner that the stick tended to move in the direction of the initial roll. This action occurred too late to constitute a warning, however. The movements of the controls required for trimming during the stall approach were never great enough to be considered important as stall warnings. Figure 52 is a time history of a stall showing the typical absence of warning and ensuing motions of the airplane when the controls were fixed at, the stall break."

 

[Riderocket]

There's an interesting point about the "XFL-1 Airabonita" which was essentially a P-39 but with a tail dragger wheel system. I must say it doesn't look as good as the P-39s Tricycle wheels.

[Rjel]

I think this will be helpful to remember when we get the P-39.

 

[Irgendjemand]

I think this will be helpful to remember when we get the P-39.

 

Nice. The energyloss from a stall seems to be quite drastic. Will be very interesting what the devs model with this plane. Finally an awesome allied plane. Looking forward to actually flying this one. Not just buying:)

[Trooper117]

And this is how shit starts in these forums.

 

 

Stop talking rubbish... in real life the P-39 stall killed a lot of pilots...

In the old IL2 I flew the P-39  many times and yes, that stall caught many people out and some never learned how to get out of it in game.

 

Me stating that it will catch people out in game this time is not sh+t... it's a warning for people to be prepared, nothing more, nothing less...

[Fern]

Stop talking rubbish... in real life the P-39 stall killed a lot of pilots...

In the old IL2 I flew the P-39  many times and yes, that stall caught many people out and some never learned how to get out of it in game.

 

Me stating that it will catch people out in game this time is not sh+t... it's a warning for people to be prepared, nothing more, nothing less...

I heard the P-39 out climbed the yak-1...

 

Just because another game did it doesn't mean it's right. Sounds to me that the Soviets figured out the cause and a solution to the spin. Shouldn't have anything to worry about until ammo is spent.

 

Then the other Bell test pilot says it was just a Lomcevak, an air show move. Just remember most of these test probably didn't have ammo installed, unless you can prove it.