Definition
A function of certain helicopter flight management or autopilot/coupled navigation systems that automatically transitions the active navigation source from one signal or waypoint to the next as the aircraft progresses along a programmed route or instrument procedure. It is a system mode, not a pilot-selectable navigation aid, and its behavior is defined by the specific helicopter's flight manual.
Plain English
A mode in the helicopter's navigation system that automatically switches from one navigation signal or waypoint to the next at the right moment, so the aircraft keeps following the planned route without the pilot having to retune or reselect anything.
Context Anchor
Seen in helicopter flight manual limitations and avionics setup procedures for IFR helicopter operations, especially when preparing to fly an instrument approach.
Derivation
NAV is the common aviation short form of navigation, from older words meaning to direct or steer a vehicle on a route. Change over means to switch from one selected source or condition to another, which matches the aviation use here: switching which navigation source is being used for guidance.
Why Pilots Care
Confirms the aircraft can maintain continuous accurate guidance through procedure transitions without manual intervention.
Grounding Statement
When this mode changes, the guidance the pilot sees or the autopilot follows may begin coming from a different navigation source.
Intuition Check
Do not assume NAV Change Over mode means simply changing a radio frequency. Here it means the mode that controls which navigation source is feeding the helicopter’s guidance system.
Example Sentence 1
The Rotorcraft Flight Manual prohibits use of NAV Change Over mode below the final approach fix.
Example Sentence 2
Flight manual limitations require verification of NAV Change Over mode function during preflight checks for IFR flights.