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B767Driver · May 11th, 2006, 19:49

I'm trying to find a good explanation of why the indicated airspeed for Vx increases as altitude increases.

I understand the reason for the indicated Vy decrease...available horsepower decreases and shifts the maximum excess thrust to a lower speed.

Obviously, Vx is excess thrust dependent. As airspeed increases...thrust drops off fast. So why is maximum excess thrust for a prop airplane found at a higher airspeed as altitude is gained.

I'm having trouble finding a good explanation for this.

May 11th, 2006, 19:49	#1
B767Driver Old Skool Join Date: Sep 2003 Posts: 1,847	Vx and altitude I'm trying to find a good explanation of why the indicated airspeed for Vx increases as altitude increases. I understand the reason for the indicated Vy decrease...available horsepower decreases and shifts the maximum excess thrust to a lower speed. Obviously, Vx is excess thrust dependent. As airspeed increases...thrust drops off fast. So why is maximum excess thrust for a prop airplane found at a higher airspeed as altitude is gained. I'm having trouble finding a good explanation for this.