Definition
The loss or significant degradation of an aircraft's navigation equipment, such that it can no longer reliably determine position, track, or guidance to a destination or along an airway. Causes include antenna icing, receiver malfunction, loss of signal reception, power loss to the unit, or interference with the navigation source.
Plain English
The equipment the pilot uses to find their way is no longer working properly, or has stopped working entirely.
Context Anchor
Seen in instrument flying and antenna icing discussions, where ice on an antenna can weaken or block the signals the navigation equipment needs.
Why Pilots Care
Loss of reliable navigation forces reliance on backup methods or immediate diversion to maintain safety during instrument flight.
Intuition Check
Do not assume failure means the unit must be dark or completely off. In flying, a navigation system failure can also mean the system is still showing information, but that information is unreliable.
Example Sentence 1
After picking up ice on the antenna, the pilot suspected a navigation system failure when the course needle began drifting erratically.
Example Sentence 2
The crew noticed the navigation system failure on the approach and immediately executed the published missed approach procedure.