What is a disadvantage of turbojet engines?

• A. Provides excellent takeoff performance on short runways
• B. Has low maintenance requirements
• C. Cannot produce exceptionally high thrust at low altitudes and airspeeds
• D. Operates more quietly than turbofans

Answer: (C)

Turbojet engines rely on accelerating air to very high exhaust speed with little or no bypass air. That design yields strong thrust only when the aircraft is moving fast enough to push a lot of air through the engine. At low airspeeds and low altitudes, the mass of air entering the engine is limited, so the thrust isn’t exceptionally high. In other words, turbojets don’t deliver great takeoff thrust at low speeds compared with other types of engines, and they burn more fuel and are louder as a result. The other statements describe characteristics that aren’t typical advantages of turbojets: they aren’t known for excellent short-field takeoff performance, they don’t generally have low maintenance requirements, and they aren’t quieter than turbofans.