What to expect from your shiny new P39-L1

[Mitthrawnuruodo]

Rear-mounted engine is not necessarily bad in terms of survivability.

 

Of course, it shields the pilot against attacks from the rear. Seat armour often seems insufficient to stop cannon rounds, so having the engine there might be quite beneficial. 

 

Often, It would be good to trade an oil or coolant leak for the pilot's life. 

[Ehret]

Often, It would be good to trade an oil or coolant leak for the pilot's life. 

 

Even more so when most sorties were over, or very close to friendly territory.

[=EXPEND=CG_Justin]

That plate is only behind the engine, it doesnt extend to its sides, top or bottom which is a problem. Considering engine was behind the pilot it was found that explosions occurring in tail section had high probability of damaging engine, plenty of evidence of that was found in New Guinea combat. 

Seeing as most online combat looks like and how often people hit tails I feel like the weakest point of P-39 will be its engine. 

 

Not only this, but the lack of side and top protection for the engine might be a big problem when being hit in high deflection situations. I notice many times, when Red pilots use their hard turning tactics, the high deflection angle has enemy projectiles impacting in an almost "top down" or "full side" pattern covering a lot of surface area. I think these types of high angle shots are going to be very detrimental to the P-39's engine as they negate the rear armor completely. A well aimed 20mm hit just aft of the cockpit coupled with a few rifle caliber shots and I think she's going to stream oil and water and get HOT in a HURRY.

 

My feeling is, the mantra for this plane will be...

 

"Aim well and make your hits count, and don't get hit...like, ever....at all.....seriously!"

 

 

On a side note, I wonder how "destructible" the air intake scoop on the top will be, and how it might adversely effect performance? If I'm not mistaken, the inlets for the water and oil rads are on the leading edge of the wing at the wing roots?

 

Really looking forward to the new update!

Edited January 29, 2018 by =TBAS=CG_Justin

[A_radek]

 

 

Not only this, but the lack of side and top protection for the engine might be a big problem when being hit in high deflection situations

Armor plate was indeed small, far back and would expose engine even to low angle deflection shots. I wonder if the optional removal of it would model cog change. As it is that far back it should have a noticeable effect.

I'm expecting mediocre performance. The slow firing cannon will make deflection shots difficult. Lack of slats coupled with little stall warning and the allison engine management won't make it a popular choice among the online fighterjocks. Still, until we get the i-153 alternatively whatever comes after bodenplate, it will for me be the fighter with the most character and I for one will enjoy trying to get proficient with it.

[Finkeren]

I don’t get this notion of the P-39’s engine being more vulnerable than any other fighter’s.

 

The engine is protected from rear attacks by an armor plate - that alone makes it better off than most fighters. To then complain that it wasn’t protected from the other sides seems a little silly. Which WW2 fighter had an engine protected by armor on all sides?

 

On the P-39 the engine occupies the same spot as the cockpit on most conventional fighters of the era. If that part of the aircraft was particularly vulnerable or more likely to be hit, it seems a better idea to have the engine there than the cockpit.

Edited January 29, 2018 by Finkeren

[=362nd_FS=Hiromachi]

It seems to be a better idea for the pilot. I tend to think of it like in Merkava tank, where engine serves as secondary protection to some degree. But it doesnt change the fact that engine is the largest object in this area and instead of being in front of the aircraft it's in the middle and rear part of it. Thus any hits in the tail section or wing root area can potentially damage it - either explosion or shrapnels. This is supported by field experiences from operating that aircraft.

Besides, the plate that protected rear part of the engine wasnt even that thick. 13 mm and 20 mm AP rounds should penetrate it. But I dont think it makes it better than in most of other fighters due to fact that there are more objects that any bullet has to pass before it recheas engine in the front of the machine - tail section, armored plate behind the pilot, seat, pilots body, front panel, fire-proof bulkhead, oil/fuel tank ... and only then it reaches engine. And some fighters also had armored plate behind control panel. 

[Ehret]

I'm expecting mediocre performance. The slow firing cannon will make deflection shots difficult.

 

To the contrary - 2 nose mounted 0.50" MG (for a punch), and (optional) 4x 0.3" MG in wings (for a "shotgun effect") plus instantaneous turn rate, and forward visibility should make deflection shots quite effective in the P39. Once you will get close (under 200m) -  not a rare occurrence at all - the 37mm will work too with some trigger discipline.

Edited January 29, 2018 by Ehret

[Aap]

Absolutely not.

It makes almost 2 rounds per seconds and unlike a machinegun you just have to hit one time to get a score.

If this kind of canons were "garbage" russians wouldn't have used it for more than 20 years with MiG 15/17/19 and so on....

 

Mig-15/17's 37mm gun had rate of fire of 400 rounds per minute, supported by 2 x 23mm with 800 rpm. 

Mig-19 had 3 x 37mm guns with rate of fire of 850-1000 rpm.

A little different than the 150 rpm we are talking about here. 

[Ehret]

Mig-15/17's 37mm gun had rate of fire of 400 rounds per minute, supported by 2 x 23mm with 800 rpm. 

Mig-19 had 3 x 37mm guns with rate of fire of 850-1000 rpm.

A little different than the 150 rpm we are talking about here. 

 

Closure rates and times for gun solutions were a little different, too.

[Finkeren]

Though I haven’t heard that it was ever done, I wonder if it would have been technically possible to replace the M4 cannon with an NS-37? It would be heavier, but also a lot more effective with around 50% gain on both rate of fire and muzzle velocity.

 

Purely speculative of course, I’m not advocating any ficticious field mods.

[A_radek]

I don’t get this notion of the P-39’s engine being more vulnerable than any other fighter’s.

 

The engine is protected from rear attacks by an armor plate - that alone makes it better off than most fighters. To then complain that it wasn’t protected from the other sides seems a little silly. Which WW2 fighter had an engine protected by armor on all sides?

 

On the P-39 the engine occupies the same spot as the cockpit on most conventional fighters of the era. If that part of the aircraft was particularly vulnerable or more likely to be hit, it seems a better idea to have the engine there than the cockpit.

 

Your right. For me it's not as much a seemingly vulnerable engine but rather all that plumbing in the rear. On a conventional fighter you would have wings, gear and all those parts taking some of it. While the pilot would be directly behind a larger piece of armor. Again this might very well be just me doubting an unconventional design and motivating that doubt with reasons that wouldn't make any real world difference.

 

 

 

Though I haven’t heard that it was ever done, I wonder if it would have been technically possible to replace the M4 cannon with an NS-37? It would be heavier, but also a lot more effective with around 50% gain on both rate of fire and muzzle velocity.

 

Purely speculative of course, I’m not advocating any ficticious field mods.

Or better yet the 23mm. Never heard of such mods. But after reading 'Red star airacobra' you realize even a shortage of american lightbulbs for the gunsight posed a problem. So replcing the gun for something home made could have made sense.

[A_radek]

To the contrary - 2 nose mounted 0.50" MG (for a punch), and (optional) 4x 0.3" MG in wings (for a "shotgun effect") plus instantaneous turn rate, and forward visibility should make deflection shots quite effective in the P39. Once you will get close (under 200m) -  not a rare occurrence at all - the 37mm will work too with some trigger discipline.

 

Not sure yet I would want the 4x 0.3. But yes admittedly the two 50's get shadowed by the presence of a 37mm, and would have a punch of their own.

[=EXPEND=CG_Justin]

To then complain that it wasn’t protected from the other sides seems a little silly. Which WW2 fighter had an engine protected by armor on all sides?

 

 

Not complaining, just observing. It's not that I think the engine will be any more vulnerable, maybe just a better target to where it sits in relation to an attacking aircraft's sight picture. Even during high deflection shots, the attack in most cases is still generally coming from the rear.

 

So far, all we have are historical accounts, and nothing but speculation about what we will get in game. I was simply speculating, as denoted by the words I have highlighted below. I am as anxious to see how she performs as anyone.

 

Hopefully it wont be long before we find out for certain.

 

Not only this, but the lack of side and top protection for the engine might be a big problem when being hit in high deflection situations. I notice many times, when Red pilots use their hard turning tactics, the high deflection angle has enemy projectiles impacting in an almost "top down" or "full side" pattern covering a lot of surface area. I think these types of high angle shots are going to be very detrimental to the P-39's engine as they negate the rear armor completely. A well aimed 20mm hit just aft of the cockpit coupled with a few rifle caliber shots and I think she's going to stream oil and water and get HOT in a HURRY.

 

My feeling is, the mantra for this plane will be...

 

"Aim well and make your hits count, and don't get hit...like, ever....at all.....seriously!"

[FTC_Etherlight]

Weapons-wise I don't see a reason to take the .30 cals ever. We all know what 2 50's can do in a Mig-3 for example, they are quite enough against fighters. The 37mm is a nice bonus against people who are not aware, attackers and bombers. It's probably not too great in a high deflection dogfight-situation but the 50's will do that job nicely anyway.

[EAF19_Marsh]

Don't know if this has any bearing on actual BoK, but historically most pilots tended to underestimate deflection and hit the aft end of the aircraft rather than the front. Possibly might lead to slightly higher propensity towards engine damage, alongside the low- / no-deflection shots crashing straight into the engine.

 

Probably marginal impact. Anyway, looking forward to flying the beastie!

[Ehret]

Weapons-wise I don't see a reason to take the .30 cals ever. We all know what 2 50's can do in a Mig-3 for example, they are quite enough against fighters. The 37mm is a nice bonus against people who are not aware, attackers and bombers. It's probably not too great in a high deflection dogfight-situation but the 50's will do that job nicely anyway.

 

For personal score, yes - the 0.3" aren't doing enough damage to secure a kill, but for a team? One quick pass and it's probable an enemy plane will leak something... not much damage, but enough to be visible thus making tracking so much easier.

 

4x Brownings add +5000 rounds/minute to the P39' rate of fire - a not trivial amount. They have a decent (500rpg?) number of rounds in the Aircobra, too; should be good for the spraying.

[Finkeren]

The .30cals could be useful for crippling bombers and Stukas. Compared to the ones on the Spitfire they do have the benefit of being placed closed together in pairs. That means, that even if you're hitting outside convergence, you're hitting with a minimum of 2 guns at a time.

[Barnacles]

I'm rather nervously wondering if it will be cold meat like the BoS P-40.

 

I don't think it will, as it will have a much better climb rate than the p40, and be significantly faster with better energy retention. It should also have the benefits of the p40, ie firepower and dive speed. I think an engagement with one from the point of view of the opposing aircraft is this:

 

You'll see them heading towards your area in a shallow dive, and be co alt but with a lot less kenetic energy, as being a clean airframe, slightly-heavier-than-a-109 aircraft, the p39 will have gathered a tremendous amount of speed. The key then will be to avoid the p39s dive attacts from hi yoyos until it has less of an e advantage. I think the 109 will then have an advantage in turn rate and climb rate so may be able to turn the tables once you are co-e.

[Herne]

My expectations for the P39 :-

1: Look around enjoying the view of the gorgeous Kuban Map

2: crap my pants when I get bounced by FW's and ME's

3. enjoy the view from my parachute.

[hedger72]

 

Or better yet the 23mm. Never heard of such mods. But after reading 'Red star airacobra' you realize even a shortage of american lightbulbs for the gunsight posed a problem. So replcing the gun for something home made could have made sense.

 

 

Happened across this particular site which claims that native weapon mods for the P-39 were indeed undertaken by the Russian:

 

http://all-aero.com/index.php/contactus/59-planes-b-c/1423-bell-p-39-airacobra

 

"Some were refitted with Soviet armament of a single Berezin 20 millimeter cannon and twin Berezin 12.7 millimeter UBS machine guns"

 

Wonder if any of this information is true? I certainly have not read it anywhere else. Curious if others more "in the know" could comment.

[Panthera]

Depending on what boost pressure we get we can also expect some pretty damn impressive low altitude speed, the aircraft achieving ~550 km/h @ SL at 57" Hg.  Climb rate is also not shabby at 3,600 to 3,800 ft/min.

 

Combined with a good turn rate I'd expect this to be quite a popular crate

[AndyJWest]

Happened across this particular site which claims that native weapon mods for the P-39 were indeed undertaken by the Russian:

 

http://all-aero.com/index.php/contactus/59-planes-b-c/1423-bell-p-39-airacobra

 

"Some were refitted with Soviet armament of a single Berezin 20 millimeter cannon and twin Berezin 12.7 millimeter UBS machine guns"

 

Wonder if any of this information is true? I certainly have not read it anywhere else. Curious if others more "in the know" could comment.

 

The full paragraph, for context:

Some late-model P-39s supplied to the USSR remained in service into the early 1950s. Some were refitted with Soviet armament of a single Berezin 20 millimeter cannon and twin Berezin 12.7 millimeter UBS machine guns; a few were even fitted with the Klimov M-105P vee-12 engine, which had a similar form-factor to the Allison V-1710.

Even if it is correct, it doesn't seem relevant to Kuban, and without more details (Which models? When? How many?) isn't much use at all.

[A_radek]

Depending on what boost pressure we get we can also expect some pretty damn impressive low altitude speed, the aircraft achieving ~550 km/h @ SL at 57" Hg. Climb rate is also not shabby at 3,600 to 3,800 ft/min.

 

Combined with a good turn rate I'd expect this to be quite a popular crate

Where did you find these numbers?

[Monostripezebra]

hopefully this:

https://youtu.be/BWwI6gZw67g?t=332

 

 

and

Edited January 29, 2018 by Monostripezebra

[Panthera]

Where did you find these numbers?

 

Here:

http://www.wwiiaircraftperformance.org/P-39/P-39N_level-speeds.jpg

and here

http://www.wwiiaircraftperformance.org/P-39/P-39Q-5_42-19615_ENG-19-1631-A.pdf

 

EDIT: Misread the speed chart, 344 mph is at 12400 ft, not SL. 329 mph (529 km/h) could be achieved at SL @ 57" Hg, still decent.

Edited January 29, 2018 by Panthera

[Cpt_Cool]

Though I haven’t heard that it was ever done, I wonder if it would have been technically possible to replace the M4 cannon with an NS-37? It would be heavier, but also a lot more effective with around 50% gain on both rate of fire and muzzle velocity.

 

Purely speculative of course, I’m not advocating any ficticious field mods.

 

A little extra weight in the nose is probably a good thing for the p-39 anyway, with the COG being so close to the center of lift. I think I remember hearing that it had stability issues if the M4 was empty (the spent brass didn't eject for this reason). anyone feel free to correct me on that point though.

[CrazyDuck]

Mig-19 had 3 x 37mm guns with rate of fire of 850-1000 rpm.

 

That's actually 3 x 30 mm (NR-30). Devastating firepower, about 18 kg per second!

[[CPT]Pike*HarryM]

One interesting small thing I've seen mentioned a couple of times re: the P-39's design is that it had the "wrong" airfoil. Some minimal searching indicated that it had a NACA 0015 (symmetrical) airfoil.

https://en.wikipedia.org/wiki/Bell_P-63_Kingcobra. The XP-39E lead to the P-63.

 

 

 

 

The resulting  XP-39E featured two primary changes from the earlier P-39D from which it was developed. One was a redesigned wing. The root airfoil, a NACA 0015 on other models of the P-39, was changed to a NACA 0018, to gain internal volume.^[3] The other was a switch to the Continental I-1430 engine, which featured an improved overall design developed from the hyper engine efforts, as well as an improved supercharger.

 

 

So why did they choose a symmetrical airfoil? It lets you fly inverted more easily (modern aerobatic planes often have symmetrical airfoils). Greater volume? The  P-39 put a lot of stuff in the wings, so maybe they needed it for required fuel load? Also at higher speeds a symmetrical airfoil would maintain efficiency better I would think as long as it was trimmed correctly. So what makes it "wrong"? Thicker chord, more drag? It looks at a glance like it would be thicker than another typical fighter of the time, like a 109 or a P-40.

Edited January 29, 2018 by [CPT]Pike*HarryM

[JtD]

0015 is 15% thickness, which is normal to thin compared to other root thicknesses used at the time. Some fighters went up to 18% thickness, many were in the 15/16% region.

 

Using a symmetrical airfoil isn't the best idea from an efficiency point of view. You need angle of attack to create lift, which typically gives you higher drag than a cambered airfoil which creates the same lift at a lower angle of attack. Also, you get a fairly low maximum lift coefficient.

On the plus side you get a constant, low moment coefficient, making strength and stability calculations easy. You don't get unwanted pitch up or pitch down behaviour from the main wing as you change angle of attack, so you can easily counteract it with the tail.

Edited January 29, 2018 by JtD

[Blitzen]

Flat upside down spins come at no extra cost!

[Panthera]

0015 is 15% thickness, which is normal to thin compared to other root thicknesses used at the time. Some fighters went up to 18% thickness, many were in the 15/16% region.

 

Using a symmetrical airfoil isn't the best idea from an efficiency point of view. You need angle of attack to create lift, which typically gives you higher drag than a cambered airfoil which creates the same lift at a lower angle of attack. Also, you get a fairly low maximum lift coefficient.

On the plus side you get a constant, low moment coefficient, making strength and stability calculations easy. You don't get unwanted pitch up or pitch down behaviour from the main wing as you change angle of attack, so you can easily counteract it with the tail.

 

Quite right, this also shone through during the NACA flight & WT tests in comparison with the NACA 66 & esp. NACA 230XX series airfoils. 

[Mac_Messer]

I`d like that single Hispano in the propeller hub!

Though I haven’t heard that it was ever done, I wonder if it would have been technically possible to replace the M4 cannon with an NS-37? It would be heavier, but also a lot more effective with around 50% gain on both rate of fire and muzzle velocity.

Purely speculative of course, I’m not advocating any ficticious field mods.

Noooooooo, ofcourse not!

[Finkeren]

I`d like that single Hispano in the propeller hub!

 

I think I read somewhere, that the VVS only received a single P-39D-1 for evaluation but ended up with most of the D-2s / P-400s. Wasn’t the D-1 the only version with a Hispano?

[Lusekofte]

I expect this plane to be successful at low medium altitud, I expect a year or two with a lot of topics about helicopter flaps, too powerful weapons and too fast to be real discussion, like all the successful Red Army fighters have been treated. I have no doubt this will perform good in this sim. But it would be a lot of opinions about it

[=WH=PangolinWranglin]

I expect another plane with instrumentation I can read, along with the A20 and Spitfire. 

 

I expect good things from the .50s, fantastic things from the 37mm (once I spend a month honing my aim), and an overall nice aircraft. I think I'll like it. I'm interested in the .30s. I'll probably try it with and without the .30s a lot. 

 

I also expect that shiny metal skin to be able to blind pilots diving on me, making them crash. 

[Stig]

successful Red Army fighters

 

 

At the same time the least successful USAAF fighter, of those that were produced and fielded in numbers; it will be interesting.

[Sgt_Joch]

It will be interesting to see what engine limits the Devs use.

 

According to the Pilot's operating instructions:

 

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

 

limits are (p.25):

 

-take off: 3000 rpm/51" boost - 5 minutes

-emergency: 3000 rpm/42" boost - 15 minutes

-continuous: 2600 rpm/37.2" boost - unlimited

 

However, 57" boost was used in flight tests of the p39Q.

 

P39Q has slightly higher limits (p.22):

 

 

-take off: 3000 rpm/50.5" boost - 5 minutes

-WEP: 3000 rpm/57" boost - 5 minutes

-military: 3000 rpm/44" boost - 15 minutes

-continuous: 2600 rpm/39.2" boost - unlimited

 

http://www.wwiiaircraftperformance.org/P-39/P-39Q-1_Operating_Instructions.pdf

 

not sure what the difference is between the V-1710-63 used in the "L" model and the V-1710-85 model engine used in the "Q", if any, that would warrant the change.

Edited January 29, 2018 by Sgt_Joch

[Panthera]

Odd with the 5 min at 50.5" and then 15 min at 57".

 

Either way as already discussed to death in the thread on the subject of WEP limits, these time limits are not actual limits but rather guidelines to maximize the TBO.

[Sgt_Joch]

Odd with the 5 min at 50.5" and then 15 min at 57".

 

Either way as already discussed to death in the thread on the subject of WEP limits, these time limits are not actual limits but rather guidelines to maximize the TBO.

 

false, but really not pertinent here.

 

you are still a relative newbie around here, but believe me, multiple threads on the P39 engine limits will appear and be endlessly discussed once the plane is released. 

Edited January 29, 2018 by Sgt_Joch

[-=PHX=-SuperEtendard]

Here:

http://www.wwiiaircraftperformance.org/P-39/P-39N_level-speeds.jpg

and here

http://www.wwiiaircraftperformance.org/P-39/P-39Q-5_42-19615_ENG-19-1631-A.pdf

 

EDIT: Misread the speed chart, 344 mph is at 12400 ft, not SL. 329 mph (529 km/h) could be achieved at SL @ 57" Hg, still decent.

For that similar ~1300 HP power, the P-39N does around 550 km/h and the P-39Q around 530 km/h. Maybe this can be explained because the Q model has .50 cals in the wings in external gunpods, if im correct this was standard in the early Q models and it's also mentioned in the report.

 

I dont know if there are significant aerodynamical differences between the N and the L, but maybe the 550 km/h value from the N can be a good approximation.

 

The -63 engine in the L had 1325 HP at 51" for 5 minutes as war emergency power.

 

There is this graph that shows around 308 mph (495 km/h) for the military power which is 42", for 15 minutes. Which is 1150 HP.

 

http://www.wwiiaircraftperformance.org/P-39/P-39K_Performance_Chart-1400.jpg

 

I have seen a picture from a Russian document showing 60" for 5 minutes for this engine, for a total of 1580 HP. It does note that this setting isn't mentioned in the official american V-1710-63 manual. I don't know if the Soviets used this very high regime.

 

But if so, I think this would increase its performance considerably maybe putting it at the high 500s km/h speeds, close to the La-5FN and 1.65 ata Fw 190 As.

 

https://forum.il2sturmovik.com/uploads/monthly_08_2017/post-16698-0-17910100-1503083316.png