When must gust locks be applied to the aircraft controls?

The application of gust locks to aircraft controls is critical for maintaining control surface position and preventing unintended movement of the aircraft when it is not being actively operated. Gust locks are specifically designed to protect against the adverse effects of wind, which can cause control surfaces to flutter or move if not secured.

When an aircraft is left unattended, especially in potentially windy conditions, applying gust locks ensures that control surfaces like ailerons, rudders, and elevators remain in a neutral or safe position, preventing any damage. This practice is part of proper aircraft ground handling and maintenance protocols, as it minimizes the risk of pilot error during pre-flight checks and secures the aircraft while not in use.

In contrast, applying gust locks only when flying in turbulence, at the end of the flight, or specifically prior to maintenance activities does not fully encompass the appropriate scenarios for their use. While applying locks during maintenance might seem logical, it does not account for situations where the aircraft is simply parked or left unattended, which is a critical point at which gust locks should definitely be used.