What speed multiplier defines the maximum range speed in cruise?

• A. 0.95 x VMD
• B. 1.32 x VMD
• C. 1.5 x VMD
• D. 1.1 x VMD

Answer: (B)

Maximizing range means getting the most distance per unit of fuel. The speed for minimum drag (VMD) is the baseline where the airplane experiences the least total drag. Cruising a bit faster than this increases parasite drag, but the aircraft covers more miles each hour, so the fuel per mile can actually decrease up to a point. When you work through the relationship between speed, drag, and fuel flow (the usual range calculation uses how fuel flow grows with speed and how distance per hour changes with speed), the optimum comes out to a speed about 1.32 times VMD. That particular multiplier reflects the balance where the gain in distance per hour outweighs the rise in fuel burn per hour, giving the smallest fuel per mile and hence maximum range. So the 1.32 × VMD figure is the best estimate for maximum range speed in cruise.