The statement 'An advantage of the turboprop is that its efficiency drops off as airspeed and altitude increase' is true or false.

• A. True
• B. False
• C. Not stated
• D. Both

Answer: (B)

Turboprop efficiency is best at moderate, lower-to-mid altitude flight. The design purpose of a turboprop is to deliver excellent fuel economy at slower cruise speeds, where the propeller can convert engine power into forward thrust with high propulsive efficiency. As airspeed and altitude increase beyond that practical envelope, the engine loses mass flow and the propeller faces thinner air and higher blade speeds, which reduces overall efficiency. The real advantage of a turboprop is efficiency at those moderate speeds and altitudes, not a decline in efficiency as speed and altitude rise. Therefore, the statement is not correct.