When is the landing gear emergency control system activated?

The landing gear emergency control system is designed to activate when the normal hydraulic system fails. This is a critical safety feature that ensures the landing gear can still be deployed in the event of hydraulic failure, allowing for a safe landing. The emergency system uses an alternative hydraulic source or system, which is essential for ensuring that the aircraft can be landed safely even if the primary system has encountered an issue.

In the case of the other options, they do not align with the operational logic of the emergency control system. During takeoff, the primary focus is on ensuring that the normal systems are functioning; if there is an emergency, the emergency systems would only come into play if there is a failure. The emergency control system does not need to operate when the main system is functioning, as it’s designed as a backup. Similarly, taxiing on wet runways does not inherently trigger the emergency control system; it functions independently of runway conditions and is activated specifically in response to failures in the normal hydraulic systems.