use indicated air speed for realistic
flight

Quote:


In real life, the airspeed gauge works off air pressure. (Edit: Before I confuse anyone, this isn't barometric pressure as it affects the altimeter. This is "wind" pressure if you like, pushing against a mechanical component in the gauge mechanism through a tube sticking out of the fuelage.) As your altitude rises, the air gets thinner and consequently the reading is artificially reduced.

Using true airspeed gives you your actual speed compared to the ground but it isn't how pilots see it in their cockpits. (You can get this figure from your GPS btw.)