Private Pilot Private Exam

Which four forces act on an airplane in flight?

1. Lift, Drag, Thrust, Weight

2. Gravity, Thrust, Lift, Mass

3. Lift, Yaw, Thrust, Drag

4. Weight, Thrust, Drag, Pressure

The correct answer is: Lift, Drag, Thrust, Weight

The four forces that act on an airplane in flight are lift, drag, thrust, and weight. Understanding these forces is crucial for pilot training and aircraft performance. Lift is the aerodynamic force that acts perpendicular to the relative wind and supports the airplane in the air. It is generated primarily by the wings as air flows over and under them, following Bernoulli's principle and Newton's third law. Weight, or gravitational force, acts downward toward the center of the Earth and is the result of the airplane's mass. It must be counteracted by lift for the airplane to ascend or maintain altitude. Thrust is the forward force produced by the engines, propelling the airplane through the air and overcoming drag. Without sufficient thrust, the airplane would not maintain its speed or altitude. Drag is the aerodynamic resistance that opposes an airplane's forward motion. It is caused by friction between the air and the aircraft surfaces and by the pressure differences that occur as the aircraft moves through the air. Together, these four forces interact during flight to determine an airplane's performance, control, and stability, making this combination the fundamental concept in understanding flight dynamics.