Which term is the forward force that propels the airplane through the air?

• A. Thrust Line
• B. Torquemeter
• C. Thrust Aerodynamic Force
• D. Thrust

Answer: (D)

The forward propulsion through the air is produced by thrust—the aerodynamic force that pushes the airplane in the direction of flight. This thrust is generated by the propulsion system, such as engines with propellers or jet engines. In level flight, thrust balances drag, keeping airspeed steady. The other terms don’t describe the propulsion force: a torquemeter measures torque rather than the forward push; “thrust aerodynamic force” isn’t the standard term used; and the later notion of the thrust line refers to the direction of that force, not the force name itself.