Within terrain flight operations, which navigation method relies on external visual cues?

The chosen answer, pilotage, is the correct method of navigation that relies on external visual cues. In terrain flight operations, pilotage involves navigating by referencing prominent terrain features and landmarks that are visible to the pilot. This method allows the pilot to determine their position relative to recognizable geographical features such as mountains, rivers, towns, or roads, using visual navigation techniques.

Pilotage is particularly useful in areas where detailed maps or other navigational aids may not be available or practical. It allows pilots to maintain situational awareness and adjust their flight path based on what they can see outside the cockpit, making it a fundamental skill in visual flight rules (VFR) operations.

Other methods listed, such as dead reckoning, rely on calculations based on speed, time, and course rather than visual cues; radio navigation involves the use of radio signals and instruments; and autopilot navigation is a system that controls the aircraft without the pilot's constant input, generally utilizing programmed waypoints or radio signals rather than relying on visual observations.