Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What does propeller efficiency represent?

1. The ratio of thrust horsepower to brake horsepower.

2. The actual distance a propeller advances in one revolution.

3. The difference between the geometric pitch of the propeller and its effective pitch.

4. The thrust generated by the propeller at various RPMs.

The correct answer is: The ratio of thrust horsepower to brake horsepower.

Propeller efficiency is defined as the ratio of thrust horsepower to brake horsepower. This indicates how effectively the propeller converts the engine's power into useful work, specifically in producing thrust. Thrust horsepower reflects the actual thrust produced by the propeller, while brake horsepower accounts for the power available at the engine output, after losses due to friction and other factors. The closer the ratio is to 1, the more efficient the propeller is at converting engine power into thrust. This efficiency is a critical consideration in aviation, as it directly affects aircraft performance, fuel consumption, and overall effectiveness during flight. Understanding this concept allows pilots and engineers to evaluate propeller performance under varying conditions and to optimize aircraft design for improved efficiency and performance. Other proposed answers refer to different aspects of propeller design or operational characteristics but do not directly define propeller efficiency itself.