P-40 Performance - Allison versus Merlin

[HoHun]

Hi everyone,

Here some graphs on the performance of the Allison- versus the Merlin-engined Curtiss P-40 fighters.

That the P-40F was not as good as one might have expected has two main reasons: It was using an early Packard-built V-1650-1 that was similar to the two-speed, single-stage 20-series Rolls-Royce Merlin and not as powerful as the later V-1650 engines fitted to the Mustang that were based on the 60-series Merlins. Additionally, the P-40F was 160 kg heavier than the P-40E, and an amazing 750 kg heavier than the P-40B, which of course had considerable impact on its performance.

(The Allison-vs-Merlin issue was raised in this thread:

http://www.ww2aircraft.net/forum/avi...mal-13759.html (P-38 with Merlin Engines? Any such animal?)

However, since that was a P-38 thread I decided to start a new one for the P-40 here.)

Regards,

Henning (HoHun)

[claidemore]

Turn rates are in degrees per second?

[HoHun]

Hi Claidemore,

>Turn rates are in degrees per second?

Oops - yes, they are!

Regards,

Henning (HoHun)

[kool kitty89]

How about adding in the P-40M?
(I think the P-40N is less comparable as there were many other changes to that model and many changes in that model its-self) And the P-40K is roughly the same as the P-40E (at normal loaded weight) except it has more power below 5,000 ft due to increased boost limit to 60" HG. (1,570 hp at ~3,000 ft)

The P-40M was basicly the P-40K with the V-1710-81 (as P-51A and P-40N) instead of the -73. The -81 having much better altitude performance due to the 9.6:1 blower (opposed to the 8.8:1 of the -36 and -73), as has been discussed before. This also had the disadvantage of lower max boost rating (than the -73) and lower max power available below ~5,100 ft.

So:

P-40M

Gross weight: 8,400 lbs

powered by one V-1710-81 with 1,200 hp takeoff,
1,125 hp at 17,500 ft millitary rating, and
1,480 hp at 10,400 ft at 57" Hg WEP rating. (1,360 hp at SL -although using 57" WEP at SL was not recomented-) These are with ram in high speed level flight.

Without ram (for climb) mil was at ~14,600 ft and
WEP at ~7,500 ft. (crit alt effectively drops by ~2,900 ft)

There's a graph for the P-51A-1 with power curves (climb and level flight) on WWII Aircraft Performance too:

[HoHun]

Hi Koolkitty,

>(I think the P-40N is less comparable as there were many other changes to that model and many changes in that model its-self)

Hm, I believe the P-40N-1 at 7800 lbs, 57" Hg is quite comparable and have included it in the comparison :-)

Note that the graphs for the P-40N decay a bit quicker with altitude than those of the other types. I suspect that is because the underlying engine graph is more accurate than those for the earlier models - during the war, a better understanding of high-altitude power developed. (And the engine graphs up high were calculated anyway.)

It was Sir Stanely Hooker who came up with an improved method of calculating high-altitude power, but unfortunately an important part of it consists of running the supercharger on a test stand to measure its performance parameters in isolation, so it's difficult to try it at home :-(

Regards,

Henning (HoHun)