To maintain constant airspeed in steady, level flight, thrust must balance which aerodynamic force?

To maintain constant airspeed in steady, level flight, thrust must balance which aerodynamic force?

• A. Drag
• B. Weight
• C. Lift
• D. Inertia

Answer: (A)

In steady, level flight with constant speed, the airplane experiences zero net force along the direction of motion. The engine’s thrust pushes forward, while air resistance creates drag backward. For the speed to stay constant, these two forces must balance each other, so thrust equals drag. Lift and weight balance each other to keep the airplane at the same altitude, but that vertical balance is separate from maintaining constant airspeed. Inertia isn’t a separate force to balance; it’s the tendency of the aircraft to resist changes in motion. So the thrust must balance the drag.

In steady, level flight with constant speed, the airplane experiences zero net force along the direction of motion. The engine’s thrust pushes forward, while air resistance creates drag backward. For the speed to stay constant, these two forces must balance each other, so thrust equals drag. Lift and weight balance each other to keep the airplane at the same altitude, but that vertical balance is separate from maintaining constant airspeed. Inertia isn’t a separate force to balance; it’s the tendency of the aircraft to resist changes in motion. So the thrust must balance the drag.