P-40E...have I lost my mind?

[ACG_KaiLae]

First, I'm no expert in this area. However, I got to thinking. I drive around in the P-40 a fair amount. Getting anything done with this plane is hard; it's sort of like killing something with a LaGG. You get extra style points for doing so lol. However, one thing I noticed was that unless I was diving on something, I never saw the speed much over 300 MPH. I recall this plane having a top speed of something like 350 MPH. I looked up some documents online (later found they were not for the P-40E) which said top speed was at 15,000 feet. So I was curious, put the plane up at 15,000 and ran it with throttle fully open, and 2600 RPM. Top speed - 250 MPH. Ok, so I tried combat power, 2800 RPM. Top speed, 270-275 MPH (I ran RPM up until technochat said emergency, so just under 2900 RPM I recall to test that). 

 

I left the server, and looked up the documents online for the P-40E:

 

http://www.wwiiaircraftperformance.org/P-40/P-40E_40-384_PHQ-M-19-1300-A.pdf

 

http://www.wwiiaircraftperformance.org/P-40/P-40E_40-633_FS-M-19-1580-A.pdf

 

Now, it actually says max speed at 11,400 feet of 342 MPH. But, it also lists a series of tests done at about 15,000 feet as well, under varying conditions (drop tank, no drop tank, various propellers, etc). At cruise power - which I'll take it to mean throttle fully open since at this alt manifold pressure is about 37" - and 2600 RPM, listed test speed is about 310 MPH.

 

Now, as I said, I'm no expert, but is something off here? Have I missed something? In short, could someone more knowledgeable check this out please and see if I have done something wrong (probable) and if the plane is off (maybe possible?).

[JtD]

Do you know the difference between indicated air speed (IAS), which you see on the HUD and your speed gauge, and true air speed (TAS), which is the speed your aircraft is actually moving at?

 

If you don't, this would probably explain most of it - 250mph IAS at 15000feet being 320mph TAS.

[ACG_KaiLae]

No, thanks for pointing that out. Was going off the speedometer in the cockpit.

[JtD]

Well, in that case, a conversion calculator and what wiki has to say about IAS and TAS. Personally, if I measure speeds in game, I'm taking a stop watch and measure the time I need from one grid line to another, at least 10, better 50km away. This will give you the true speed without any conversion calculations.

 

http://indoavis.co.id/main/tas.html

 

https://en.wikipedia.org/wiki/Indicated_airspeed

 

https://en.wikipedia.org/wiki/True_airspeed