Private Pilot Private Exam

What is the relationship of lift, drag, thrust, and weight when the airplane is in straight-and-level flight?

1. Lift is greater than weight; thrust is less than drag.

2. Lift equals weight; thrust equals drag.

3. Lift is less than weight; thrust equals drag.

4. Lift equals drag; thrust is greater than weight.

The correct answer is: Lift equals weight; thrust equals drag.

In straight-and-level flight, the forces acting on the airplane are balanced to maintain a constant altitude and speed. Lift is generated by the wings, opposing the force of weight, which acts downwards due to gravity. For the airplane to maintain level flight, lift must equal weight, ensuring that the airplane neither climbs nor descends. Simultaneously, thrust, which is produced by the engines, must equal drag, the aerodynamic resistance opposing the airplane's forward motion. This balance ensures that the airplane maintains a constant speed. Thus, in straight-and-level flight, both lift is equal to weight, and thrust is equal to drag, confirming that the airplane remains stable and level.