FAA Powerplant Written Practice Test

Which type of engine is most efficient for an aircraft operating at 300mph at altitudes between 20,000-25,000 ft?

1. Piston Engines

2. Turbine Engines

3. Turboprop Engines

4. Straight Jet Engines

The correct answer is: Turboprop Engines

Turboprop engines are specifically designed to operate efficiently at the altitude and speed range mentioned, making them the ideal choice for aircraft flying at 300 mph between 20,000 and 25,000 ft. Turboprops combine the efficiency of a piston engine at lower speeds with the power of a jet engine, utilizing a turbine to drive a propeller. This configuration allows them to achieve better fuel efficiency compared to pure jet engines at lower speeds, which is particularly advantageous for missions requiring a balance of speed and efficiency at the stated altitudes. While piston engines can also operate effectively at lower altitudes and speeds, they generally become less efficient as altitude and speed increase due to factors like reduced air density and the limitations of engine power output. Jet engines, on the other hand, excel at higher speeds and altitudes but can be less fuel-efficient in the subsonic range. Given that turboprops are optimized to operate effectively in the region where the question specifies, they stand out as the most efficient option for this application.