What is the lift-to-drag ratio and why is it important for cruise efficiency?

• A. L/D = lift divided by drag; higher L/D means more efficient cruise and less fuel burn
• B. L/D = drag divided by lift; higher L/D means more drag
• C. L/D = lift times drag; higher L/D improves acceleration
• D. L/D = lift minus drag; higher L/D reduces stability

Answer: (A)

Lift-to-drag ratio is a measure of how effectively the wing can generate lift relative to the drag it creates. It’s defined as lift divided by drag. In steady, level cruise, lift equals the aircraft’s weight, so a higher L/D means you can produce that weight support with less drag. Less drag means the engines or motors don’t have to work as hard to maintain the same cruise speed, which translates to lower fuel burn and greater range. The speed that gives the maximum L/D is the most fuel-efficient cruise condition because it minimizes the power needed for a given airspeed. The other options mix up the relationship (drag divided by lift, lift times drag, or lift minus drag) and don’t reflect how efficiently a aircraft travels through the air.