Which engine type uses the bypass to create additional thrust by diverting a secondary airflow around the combustion chamber?

• A. Turbojet engine
• B. Turboprop engine
• C. Turboshaft engine
• D. Turbofan engine

Answer: (D)

This question centers on how bypass air adds thrust in a turbofan engine. A turbofan uses a large front fan that moves air, and a portion of that air goes into the engine core for combustion while a larger portion is diverted around the core through a bypass duct. The bypass air does not pass through the combustion chamber; it is accelerated by the fan and exits through a nozzle, contributing additional thrust. This arrangement gives high overall propulsion efficiency and lower fuel burn at subsonic speeds, along with reduced noise, compared with engines that rely almost entirely on core exhaust. The other engine types either don’t use a bypass around the core or rely on a propeller/rotor to produce thrust, so they don’t generate thrust from a bypass stream in the same way.