To maintain long-range cruise as weight decreases due to fuel burn, what action should the pilot take?

• A. Reduce thrust and reduce airspeed
• B. Increase thrust and reduce airspeed
• C. Maintain thrust and increase airspeed
• D. Reduce thrust to maintain best L/D ratio

Answer: (A)

Efficient long-range cruise occurs near the speed for the best lift-to-drag ratio. As fuel is burned, weight drops, so the lift required decreases and the speed that gives the best L/D shifts to a lower value. To stay at that efficient point, you should reduce both airspeed and the corresponding thrust to match the reduced drag and lift needs. Pushing thrust up or maintaining a higher speed would increase fuel burn and move away from the most efficient cruise. Reducing thrust alone without slowing to the lower optimal speed wouldn’t optimize efficiency, so lowering both parameters keeps you in the most economical cruise condition.