About Mach speed

[Theone05 0]

So, i'm just wondering, how is it possible that example F-15 has topspeed of 2.5 Mach. Still, i have been able to reach barely only mach 2.0 in Lock On (Just as an example). So the thing that i'm asking, how do you really measure those speeds? Should it be at level-flight or diving down at high altitudes?

[DWCAce 19]

typically it's measured straight and level, and at different altitudes. The higher the altitude, the higher your true airspeed will be. Also, the loading of the aircraft is a big factor. If you are carrying external stores, your drag and weight are increased.

[PG_Raptor 0]

Mach numbers are not the same thing as airspeed. Actually, there are a lot of different types of airspeed, but we'll stick with true and mach. True airspeed is how fast you are moving through the air. You're mach number is the true airspeed relative to the speed of sound. As Dwcace said, it depends on your altitude. At sea level, the speed of sound is 776 mph. As you go up in altitude, the air gets thinner, and the speed of sound drops. Something like 640 mph at 30000 ft. Therefore, if you are traveling at the same true airspeed, your moach will be higher at altitude then at the ground. It really doesn't matter whether your flying level or climbing or descending, the instantaneous mach will be the same, though it will tend to get lower as you descend, higher as you climb. Etc. Did you get that, or do I need to rephrase myself? :D

[TheoneOnly 0]

Thanks a lot guys. Problem solved.

 

 

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