P-39Q performance

[oboe]

I ran across this document on P-39Q performance and made some tests to compare to our P-39Q in game.

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

I tested offline with fuel burn multiplier set to 1.00.   My take off weight with 100% (120 gal) fuel was 7464 lbs, less than the report's listed weight of 7871 lbs (they had underwing gun pods mounted, although if I mounted them, my weight was still less than theirs).   I ran the engine with full WEP and matched their numbers of 3000 rpm and 57 in Hg, more or less depending on altitude.

While I was able to match perfectly the max speed of 374 mph at 10,000 ft, my climb performance was less than their maximum value of 3805 fpm at 7400 ft.  In fact, I was unable to exceed 3200 fpm, no matter how I played with the speed setting in auto climb (I tried it at default of 160-165mph, and also tried 175 and 185 mph settings).  Best climb I saw in the E6B display was 3185 fpm.

Pretty cool to have access to such old data, though I'm confused why my climb rate was less than they achieved, even though my aircraft's weight was less - and yet I got same max speed as they reported.

<S>

[Vraciu]

Clearly Hitech has nerfed the P-39.      

[bustr]

Can you find Bell test docs for the first factory release of the 39-Q before the test data you linked. Best I can tell Hitech uses the first released for duty data and not later data like the fact the P51-D flew over the continent burning 150-Oct and a higher Max manifold than our's runs at in the game.

[oboe]

Hi Bustr,

Not sure I could find those docs, I just ran across these.  But honestly what could be better than actual flight test data, with tests conducted by the AAF, on delivered aircraft in combat trim?    The cynic in me suspects that data released by the factory/manufacturer on the first airframes for a particular a/c might be on the optimistic side of the actual a/c's performance...

I was wondering too if there could be something off/wrong about my testing method.   The document does go into much detail about the condition of the test aircraft, however it doesn't list the octane rating of the fuel used.

[RODBUSTR]

Yin Yang of Aces High.  Some low, some high,    Try  the Tempest  AH claimed initial climb rate with WEP around 4600 fpm, but will clearly do 6500fpm. try It.  take off speed to 280mph and pull back on the stick.   

[atlau]

But can it sustain it?

I assumed the autospeed climb gave you the optimum climb speed. Am i mistaken?

[oboe]

But can it sustain it?

I assumed the autospeed climb gave you the optimum climb speed. Am i mistaken?

The Airacobra was able to sustain each of the autospeed values I tested with - the default was about 160 mph but it
was also able to maintain 175 and 185 climb speeds.

I am not sure auto speed gives the optimum climb speed for each airframe.  It seems to be around 160 mph for all the aircraft I've tried.   It may be just set to a generic 160 mph for every aircraft...

[atlau]

No the autospeed climb rate is different by plane. P51 is like 175 vs 155 or so for the f4u

[nrshida]

Yin Yang of Aces High.  Some low, some high,    Try  the Tempest  AH claimed initial climb rate with WEP around 4600 fpm, but will clearly do 6500fpm. try It.  take off speed to 280mph and pull back on the stick.   

What you describe is not sustained climb rate.


Good research Oboe, hope you get your plane fixed.

[FLS]

The Airacobra was able to sustain each of the autospeed values I tested with - the default was about 160 mph but it
was also able to maintain 175 and 185 climb speeds.

I am not sure auto speed gives the optimum climb speed for each airframe.  It seems to be around 160 mph for all the aircraft I've tried.   It may be just set to a generic 160 mph for every aircraft...

It's likely the best lift/drag speed which is why it's similar in contemporary fighters.

[Krusty]

It is calculated per aircraft and not an across-the-board default.

[haggerty]

Would be awesome if the P-39 could climb at 3800ft/min.  I'd definitely use it way more often.