When is the landing gear considered to be locked down?

The condition of the landing gear being locked down is primarily established through the function of the overcentre mechanism. This mechanism is designed to ensure that the landing gear remains securely in the down and locked position during the landing phase. Once the landing gear is extended and the overcentre mechanism engages, it prevents the gear from retracting inadvertently, providing the necessary safety and stability for landing.

While other indicators, such as lights and alignment with wheel wells, may provide additional assurance about the landing gear status, the critical factor for determining that the gear is locked down is the secure engagement of the overcentre mechanism. This operational principle is vital to flight safety, as an improperly locked landing gear could lead to catastrophic failure during landing.