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-   -   Demo P-51 and Spitfire Top Speed (http://forum.fulqrumpublishing.com/showthread.php?t=8507)

Marchochias 08-01-2009 06:55 AM

Quote:

Originally Posted by SleepTrgt (Post 86006)
ive come close to 375 Mph level flight.

At what altitude? Was this with speed from a dive, or just gaining speed by going level?

I tried bringing the P-51 to 20 000 feet and diving, it reached 492 mph in the dive but the speed dropped off quickly after levelling.

The highest I could reach at very low altitude was 280 mph.

Does anyone know if the speed indicator is showing true airspeed or indicated airspeed?

TexRoadkill 08-01-2009 08:24 AM

If they fly at the same speed no matter what the altitude then they must be using true air speed. If it they were using IAS then you would probably see the speed closer to 400-500 mph when flying under 10,000 ft.

IceFire 08-01-2009 12:47 PM

I haven't finished the download yet but if BoP is doing things right then the speed you're seeing listed is called Indicated Air Speed (IAS). The top speed of aircraft that you see published in books and so forth is listed in True Air Speed (TAS). The Mustang will top out at 437mph TAS (D model) or 439mph TAS (B/C models) in the 25,000 feet range where the difference between IAS and TAS will be quite high. At sea level IAS and TAS are the same.

The difference is that air at higher altitudes is thinner thus the measurement will be different for speed. TAS corrects for that difference and measures your actual speed across the ground.

Marchochias 08-02-2009 12:23 AM

Yeah I know what IAS and TAS are, I just didn't know which one IL-2 BOP is using because it doesn't specify.

Since the maximum speed is so much lower at sea level, how fast was a P-51D supposed to be able to go at sea level or very close to it?

Also, do you know what the "WEP" throttle setting is? I'd never heard of such a thing before.

DigitalMan 08-02-2009 12:35 AM

Quote:

Originally Posted by Marchochias (Post 86361)
Also, do you know what the "WEP" throttle setting is? I'd never heard of such a thing before.

War Emergency Power. Pilots referred to it as pushing the throttle "through the gate." It would burn up fuel pretty quickly, but since we have unlimited we can push the throttle through the gate forever in the game.

IceFire 08-02-2009 02:22 PM

Quote:

Originally Posted by Marchochias (Post 86361)
Yeah I know what IAS and TAS are, I just didn't know which one IL-2 BOP is using because it doesn't specify.

Since the maximum speed is so much lower at sea level, how fast was a P-51D supposed to be able to go at sea level or very close to it?

Also, do you know what the "WEP" throttle setting is? I'd never heard of such a thing before.

Try this: http://www.wwiiaircraftperformance.o...stangtest.html

According to the top test a standard P-51B Mustang operating at 60.5" Manifold Pressure reaches 363 MPH TAS at 5000 feet. Thats the lowest altitude they test for on that one. There are a variety of other tests available but they use higher pressures in the engine and better grades of fuel. Have a look...but be warned there's lots of information :)

WEP is war emergency power. On the Mustang it'll include a bump up in boost pressures as well as water injection to keep the engine from exploding.

Marchochias 08-02-2009 09:01 PM

Thanks for the info.

After getting the hang of the controls a bit more, I got the P-51D up to 300 mph level flight at very low level (under 2000 ft).

Still slow to accelerate, but very quick to climb.

juz1 08-02-2009 09:35 PM

how about your flaps? (snigger...)

keeping flaps raised and trim sorted with the stang really helped me...got into dogfighting the 190s (quick buggers! )...adjusting the flaps back to raised from combat as soon as you don't need the stability...and the stang is loaded with rockets at the start..
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