Where does maximum range occur in a propeller-driven airplane?

Maximum range in a propeller-driven airplane occurs at maximum lift/drag ratio because this point represents the most efficient use of the airplane's aerodynamic capabilities. The lift/drag ratio is a crucial measure of an aircraft's efficiency in converting thrust to produce lift while minimizing drag. When an airplane operates at this optimal ratio, it can maintain flight over a longer distance for a given amount of fuel.

In practical terms, achieving maximum lift/drag ratio often involves flying at a specific airspeed that balances lift and drag, ensuring that the airplane can glide the farthest without requiring thrust from the engine. This efficiency becomes particularly relevant during long-distance flights where the goal is to extend range effectively.

While maximum thrust can produce high speed and altitude, it may lead to increased drag that detracts from overall efficiency. Maximum speed does not consider fuel consumption in relation to distance traveled, and minimum weight, while reducing drag and increasing range, does not directly relate to optimal performance in lift generation and drag reduction at steady cruise conditions. Thus, emphasizing the lift/drag ratio leads to enhanced aerodynamic efficiency and the longest range possible for the flight mission.