FAA Part 107 Drone Practice Test

What action causes a stall in a UAS?

1. Exceeding the maximum speed

2. Exceeding the maximum allowable operating weight

3. Exceeding the critical angle of attack

4. Flying in adverse weather conditions

The correct answer is: Exceeding the critical angle of attack

Stalling in a UAS (Unmanned Aircraft System) occurs when the aircraft exceeds the critical angle of attack. The critical angle of attack is the angle between the wing's chord line and the oncoming airflow at which the wing can no longer generate adequate lift. When this angle is exceeded, the airflow separates from the wing's upper surface, leading to a significant loss of lift. Understanding the dynamics of lift is crucial for UAS operation, as it helps pilots maintain control and avoid potentially dangerous situations. If a pilot inadvertently maneuvers the UAS at too high of an angle relative to the airstream, the wings become unable to support the weight of the aircraft, resulting in a stall. Although other factors, such as weight and speed, can impact overall aircraft performance and handling, exceeding the critical angle of attack is the specific action that directly leads to a stall condition. This is why managing the angle of attack is vital in flight operations to maintain a safe and controlled flight environment.