Which aircraft system is crucial for a safe landing in case of an engine failure?

The landing gear is essential for a safe landing in the event of an engine failure because it is the system that directly supports the aircraft's touchdown and helps absorb the impact when landing. When an engine failure occurs during flight, the pilot must ensure a safe approach and landing, and the landing gear must be deployed properly to facilitate landing on the runway.

In this scenario, the other systems do play roles in flight operations, but they do not directly correlate with performing a safe landing after engine failure. The navigation system assists with guidance to the landing site, but it does not contribute physically to the landing process. Thrust vectoring, which involves manipulating engine thrust direction to enhance maneuverability, is not relevant when an engine is non-functional since it relies on the engine's performance. Lastly, while the autopilot can aid in handling the aircraft during flight, it does not take over the crucial physical aspects of landing when engine power is lost. Therefore, the landing gear is the fundamental system that directly ensures a safe landing in case of engine failure.