P-39 Engine Control

[=WH=PangolinWranglin]

Will it be as annoying as the P40's Allison? Were there any automatic controls? And will it be any different because it is running its power through a shaft to the propeller of the aircraft? 

[Sokol1]

Based on this video, yes.

 

 

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

Edited October 5, 2016 by Sokol1

[Finkeren]

Honestly the most annoying part of running the P-40E-1's engine is the draconian time limit and MP-constraints.

 

There is no doubt, that the engine controls will be rather similar on the two planes, except for the cooling which will likely be slightly more complex and less effective in the P-39 than the simple and very effective system on the P-40. So yes, the engine will have quite complex controls.

 

However, there is no way of telling how the devs will handle the limitations on the engine. The P-40E-1 has the V-1710-39, while the P-39L has the considerably improved V-1710-63, which at least nominally produces an extra 175hp at take off. The limits on this engine might be modelled less restrictive than the P-40's, since the limits were greatly loosened up on the V-1710 over the course of its development.

 

So yeah: Controls will be complex, but it just might be, that there will be less reason to adjust them all the time.

[Cpt_Branko]

No automatic boost control.

 

Anyway, V-1710-39 and V-1710-63 do not differ very much. The V-1710-39 produces virtually the same amount of power at the same manifold pressure. Not sure if it's going to be true ingame (engine management is a bit weird). Actually let's relate the engines a bit better. The V-1710-35 used on earlier Airacobras (P-39D) was very similar to V-1710-39 (used on the P-40E), except adapted to the P-39. Similarly, the V-1710-63 as used on P-39K/L is a sibling engine to the V-1710-73 used on P-40K. The two (-63, -73) differed in propeller reduction gear from the earlier generation (-35 and -39), and there might have been some strenghtening of components (I found mention of it somewhere, but I'm not positive on this).

 

We know for a fact that in December 1942, on the V-1710-39 it was allowed to use of up to 57" Hg as a war emergency rating for duration of 5 minutes, and on the V-1710-73 as used on P-40K it was also in December 1942 allowed to use up to 60" Hg as a war emergency rating for duration of 5 minutes. This was not a result of any changes on the engines, but rather different instructions of use; by all indication it was a result of crews already misusing the engine (no automatic boost control, so).

 

Actually the limits for the P-39K/L outlined in the manual which is available on WWIIaircraftperformance were amended 1944 (much of the manual was amended at that date). There's no definitive document on the engine limitations at the time of the production of the P-39K/L series (likely similar to initial limitations of V-1710-73, for which the January 1942 table also lists 51" Hg takeoff rating as maximum allowed), nor is there definitive documentation on what happened to the engine limitations of that particular engine at the time all supercharged Allison engines were uprated in December 1942. Realistically, the P-39K/L almost certainly was cleared for 57" Hg or 60" Hg at the time as it's emergency power rating, but there's just no documentation on it. As the P-39K/L models did not need an emergency power rating in 1944, this was likely amended away. It's sibling engine, the P-40K's V-1710-73 is quoted to deliver 1550 HP at sea level (with ram air) at the war emergency rating 60" Hg.

 

If you want to see the much improved version of the engine, you'd want the (much more produced, but I think left out for balance reasons) P-39N, which saw a shift to 1:9.6 blower ratio on the V-1710-85 engine, and consequent significant increase at performance at altitude with only small sacrifice of low altitude performance (realistically speaking; in game it would have higher performance at low altitude due to operating on 1943 engine limits), and of course automatic boost control. The V-1710-85 is a sibling engine to the P-40N's engine, the V-1710-81. Both featured automatic boost controls and were in December of 1942 cleared for use of up to 57" Hg as war emergency rating for duration of 5 minutes (automatic boost control was pretty much necessary on these engines, because 57" Hg brought you fairly close to detonation point unlike with earlier engines).

 

If you really care about what happens to the implementation of the P-39L, you might want to try to find a P-39K/L manual from 1943, one which wasn't amended later on. There's no definitive document on the engine limitations of the P-39K/L series at the time all supercharged (to be precise; the turbocharged Allisons as on the P-38 had a different trajectory) Allison engines were uprated in December 1942, but likely it is languishing in some archive somewhere.

Edited February 5, 2017 by Cpt_Branko

[Dakpilot]

Although the Allison engines were basically the same, during production time there were many small changes including casting and crankshaft etc.

 

without going into the minutiae of details it would not be unreasonable to expect an early-mid 43 V1710 to have a little more durability than a late 41 or early 42 one, alongside the published relaxed MP restrictions

 

Cheers Dakpilot

[Cpt_Branko]

Yes, there were production changes from 1941 to 1942. Hence the different designations of the engines over time. It's certain the engine was strenghtened, comparing the 1941-early 1942 models (like the -39 and -35) and mid 1942 models (like the -73 and -63).

 

We can infer that from both different (higher) takeoff ratings, and the fact that when the manufacturer decided to raise the limitations, the war emergency power allowances as per the manufacturer were on V-1710-39 and -35 engines 57" Hg @ 3000 RPM, while on the -73 and -63 engines, they were 60" Hg @ 3000 RPM. Since we know that detonation wasn't the limiting factor here, the difference is almost certainly due to structural strength of the engine.

 

It's possible that nothing more than takeoff rating was allowed on the P-39L if it wasn't refitted with a automatic boost control.

 

We'll see if they refine their engine failure modes in the future. If they implement more realism in this it won't be such a huge downside not to have an automatic boost control.

Edited February 6, 2017 by Cpt_Branko

[Farky]

 

No automatic boost control.

 

Anyway, V-1710-39 and V-1710-63 do not differ very much. The V-1710-39 produces virtually the same amount of power at the same manifold pressure. Not sure if it's going to be true ingame (engine management is a bit weird). Actually let's relate the engines a bit better. The V-1710-35 used on earlier Airacobras (P-39D) was very similar to V-1710-39 (used on the P-40E), except adapted to the P-39. Similarly, the V-1710-63 as used on P-39K/L is a sibling engine to the V-1710-73 used on P-40K.

 

 

Absolutely correct.

 

 

The two (-63, -73) differed in propeller reduction gear from the earlier generation (-35 and -39), and there might have been some strenghtening of components (I found mention of it somewhere, but I'm not positive on this).

 

There were also some minor changes in models -63/-73 compared to models -35/-39, like larger oil pumps, improved lubrication system, slightly improved inlet to the supercharger impeller and guide vanes.

 

 

We know for a fact that in December 1942, on the V-1710-39 it was allowed to use of up to 57" Hg as a war emergency rating for duration of 5 minutes, and on the V-1710-73 as used on P-40K it was also in December 1942 allowed to use up to 60" Hg as a war emergency rating for duration of 5 minutes. This was not a result of any changes on the engines, but rather different instructions of use; by all indication it was a result of crews already misusing the engine (no automatic boost control, so).

 

Correct. Just detail - V-1710-39 was allowed to use 56"Hg as WER, not 57".

 

 

Actually the limits for the P-39K/L outlined in the manual which is available on WWIIaircraftperformance were amended 1944 (much of the manual was amended at that date). There's no definitive document on the engine limitations at the time of the production of the P-39K/L series (likely similar to initial limitations of V-1710-73, for which the January 1942 table also lists 51" Hg takeoff rating as maximum allowed), nor is there definitive documentation on what happened to the engine limitations of that particular engine at the time all supercharged Allison engines were uprated in December 1942.

 

We know limits for V-1710-63 after December 1942, see picture (from Allison manual). But, engine and aircraft are two different things. Although engine (-63) had allowed limit 60"Hg for 5 minutes (WER), this was allowed only on engine/airplane with boost control (automatic manifold pressure regulator in US terminology). Since P-39K / L was not equipped with this device, therefore could not use WER, at least not officially. What was technically possible is of course a completely different story.

 

 

 

Realistically, the P-39K/L almost certainly was cleared for 57" Hg or 60" Hg at the time as it's emergency power rating, but there's just no documentation on it. As the P-39K/L models did not need an emergency power rating in 1944, this was likely amended away. It's sibling engine, the P-40K's V-1710-73 is quoted to deliver 1550 HP at sea level (with ram air) at the war emergency rating 60" Hg.

 

I will repeat my self, but this is very important - engine was cleared for 60"Hg, not the airplane. Two different things (at least in this case and also in case of P-40E). In terms of V-1710-63 performance, here is power chart -

 

 

 

 

without going into the minutiae of details it would not be unreasonable to expect an early-mid 43 V1710 to have a little more durability than a late 41 or early 42 one, alongside the published relaxed MP restrictions

 

Cheers Dakpilot

 

Production of V-1710-35/-39 ended in April/May 1942, production of V-1710-63/73 started in April/March 1942 (and ended July/August 1942). All four engines were very similar, but you are right - V-1710-63/-73 was little bit "stronger" ( with regard to durability).

There were no major changes in construction (like diferent casting or crankshaft), perhaps with the exception of elimination of backfire screens during production of -35/-39 and introduction of "streamline manifolds" nearly at the end of production run of -63/-73.

 

EDIT:

 

 

It's possible that nothing more than takeoff rating was allowed on the P-39L if it wasn't refitted with a automatic boost control.

 

Absolutely correct.

 

 

[=FB=VikS]

We know limits for V-1710-63 after December 1942, see picture (from Allison manual). But, engine and aircraft are two different things. Although engine (-63) had allowed limit 60"Hg for 5 minutes (WER), this was allowed only on engine/airplane with boost control (automatic manifold pressure regulator in US terminology). Since P-39K / L was not equipped with this device, therefore could not use WER, at least not officially. What was technically possible is of course a completely different story.

 

wer63.JPG

Do we really know about december 1942? (except "allison abuse" document by RAAF) cause this picture can be from a third edition of F-type engines manual, which printed date noted as 30th april 1944

 

 

I will repeat my self, but this is very important - engine was cleared for 60"Hg, not the airplane. Two different things (at least in this case and also in case of P-40E). In terms of V-1710-63 performance, here is power chart -

 

power chart E6.jpg

btw - from which document this picture?

[Farky]

Do we really know about december 1942? (except "allison abuse" document by RAAF) cause this picture can be from a third edition of F-type engines manual, which printed date noted as 30th april 1944

 

You are right, this picture is from Allison manual dated April 30, 1944. However, we are sure that War Emergency Ratings were allowed on V-1710s no later than in December 1942. For example, we can see War Emergency Ratings in USAAF Technical Order No. 03-10HA-5 dated November 30 1942 -

 

 

Allison V-1710 Adjustment of Regulator.pdf

 

 

btw - from which document this picture?

 

That power chart is scan from book "Vee's For Victory!" (ISBN 0-7643-0561-1), page 165. I don't know if this is copy of document from Allison company or from Wright Field (i.e. USAAF). We can try to contact the author of the book (Daniel D. Whitley) and ask him. Anyway, this power chart is same for V-1710-35, 39, 63 and 73, with the exception of a lower Manifold Pressure limit for War Emergency Rating in models -35/-39 of course. All four engines produced at the same Manifold Pressure and the same RPM same power. But I am pretty sure you know that.

 

Power chart for V-1710-35 (via "Vee's For Victory!") -

Power chart for V-1710-39 (RAF manual Mustang I) -

[Venturi]

Allison was covering their behind with conservative ratings, which was encouraged by strict USAAF requirements for equipment durability. 

 

No automatic boost regulator = overboosting by pilots in the field.

 

Multiple historical (but anecdotal) accounts of the engine surviving just fine with this abuse should inform the possible time limits in game.

 

Moot point if the airframe does not also perform as it should.

 

Thank you.

[=FB=VikS]

However, we are sure that War Emergency Ratings were allowed on V-1710s no later than in December 1942. For example, we can see War Emergency Ratings in USAAF Technical Order No. 03-10HA-5 dated November 30 1942 -

 

Allison V-1710 Adjustment of Regulator.pdf

btw - what is the source of this document? (web site?) Just curious - maybe there some more interesting stuff there  

 

 

That power chart is scan from book "Vee's For Victory!" (ISBN 0-7643-0561-1), page 165. I don't know if this is copy of document from Allison company or from Wright Field (i.e. USAAF). We can try to contact the author of the book (Daniel D. Whitley) and ask him. Anyway, this power chart is same for V-1710-35, 39, 63 and 73, with the exception of a lower Manifold Pressure limit for War Emergency Rating in models -35/-39 of course. All four engines produced at the same Manifold Pressure and the same RPM same power. But I am pretty sure you know that.

 

Power chart for V-1710-35 (via "Vee's For Victory!") -

power chart E4.jpg

Power chart for V-1710-39 (RAF manual Mustang I) -

power chart F3R.JPG

rgr, thanks!

[Farky]

 

 

btw - what is the source of this document? (web site?) Just curious - maybe there some more interesting stuff there

 

This document was posted about year ago on this forum by NZTyphoon, I don't know original source.

[=MG=Dooplet11]

Good day!

Modes of operation V1710-39 , -63, and the period of these modes do not remain without attention and the Russian part of the community:

 

https://forum.il2sturmovik.ru/topic/5644-r-40-i-r-39-dva-samoleta-odin-dvigatel/page-1

 

https://forum.il2sturmovik.ru/topic/5644-r-40-i-r-39-dva-samoleta-odin-dvigatel/page-5?do=findComment&comment=514614