What distinguishes turbofan engines from turboprops?

What distinguishes turbofan engines from turboprops?

• A. They are only used on military aircraft
• B. A fan replaces the propeller
• C. They do not use combustion
• D. They produce no thrust

Answer: (B)

The big idea here is how thrust is produced and what drives it in the engine. A turbofan uses a large front fan to move a lot of air directly through the engine. This fan pushes air around the engine (the bypass flow) and out the back, providing most of the thrust, especially at typical subsonic speeds, while the core still burns fuel to add some additional thrust through exhaust. In a turboprop, the turbine drives a propeller, and that propeller is the main source of thrust, with the exhaust contributing much less to overall thrust. So the statement that best distinguishes turbofans is that a fan replaces the propeller. The other choices aren’t accurate: turbofans can be used on civilian and military aircraft, they do use combustion, and they do produce thrust.

The big idea here is how thrust is produced and what drives it in the engine. A turbofan uses a large front fan to move a lot of air directly through the engine. This fan pushes air around the engine (the bypass flow) and out the back, providing most of the thrust, especially at typical subsonic speeds, while the core still burns fuel to add some additional thrust through exhaust. In a turboprop, the turbine drives a propeller, and that propeller is the main source of thrust, with the exhaust contributing much less to overall thrust.

So the statement that best distinguishes turbofans is that a fan replaces the propeller. The other choices aren’t accurate: turbofans can be used on civilian and military aircraft, they do use combustion, and they do produce thrust.