Which statement accurately describes a turbojet engine?

• A. A ducted fan engine.
• B. A turboprop that uses propeller thrust.
• C. An electric propulsion system.
• D. A turbine engine which produces its thrust entirely by accelerating the air through the engine.

Answer: (D)

Understanding turbojet operation means recognizing how thrust is produced in a pure turbine jet. A turbojet accelerates air that flows through the engine and out the nozzle. The compressor compresses incoming air, fuel is burned, and the high-energy gases expand through the turbine and then exit the nozzle at high speed. The thrust comes from this rapid acceleration of a large mass of air, with no separate propulsive device like a fan or propeller.

That description matches a turbine engine whose thrust is generated entirely by accelerating air through the engine. A ducted fan engine (turbofan) uses a large fan to produce additional thrust; a turboprop relies mainly on a propeller for thrust; an electric propulsion system uses electric motors rather than combustion-driven jet exhaust.