Drone Pilot Practice Exam

When does lift generally become unstable in fixed-wing aircraft?

1. During steady climbs

2. During stalls

3. During fast descents

4. During level cruising

The correct answer is: During stalls

Lift becomes unstable in fixed-wing aircraft during stalls. A stall occurs when the angle of attack exceeds a certain critical value, causing the airflow over the wings to become turbulent and separating from the wing's surface. This separation leads to a significant loss of lift, which can drastically affect the aircraft's ability to maintain altitude or control. In this state, the aircraft may experience a sudden descent, and pilot skills become critical in recovering from the stall. Other flight conditions – such as steady climbs, fast descents, and level cruising – typically maintain stable lift characteristics as long as the aircraft is controlled within its operational parameters. In steady climbs, the aircraft maintains an appropriate angle of attack without exceeding the stall threshold. During fast descents, even though the aircraft is descending quickly, as long as it maintains a controlled flight path, the lift remains stable enough to keep the aircraft manageable. Level cruising operates within a stable configuration where lift equals weight, allowing consistent performance. Therefore, while all scenarios influence lift in some capacity, stalls are particularly significant for presenting instability and potential loss of control.