Question

Which factor is not a constant factor in cruise method 3?

(a) Mach number

(b) Angle of attack

(c) Altitude

(d) Relative air speed

The question was asked in a national level competition.

This intriguing question originated from Cruise Method 3 in portion Cruising Performance of Aircraft Performance

Answer 1

The correct answer is (d) Relative air speed

To elaborate: The factor that must be reduced in cruise method 3 (also known as constant angle of attack and constant altitude method) is angle of attack. Also the ratio of weight to lift coefficient and relative airspeed are kept constant i.e. W/CL ratio and u are constant throughout the method.