Definition
An onboard electronic processing unit in an RNAV system that takes signals from VOR and DME ground stations and uses them to calculate the aircraft's position relative to a pilot-defined waypoint, then drives the cockpit course and distance displays accordingly.
Plain English
A small computer in the aircraft that does the math behind area navigation. It takes in raw signals from ground-based navigation stations and works out where you are in relation to the point you want to fly to.
Context Anchor
Seen in older VOR/DME RNAV equipment discussions, especially when the handbook explains how the aircraft calculates navigation guidance from ground-based radio aids.
Why Pilots Care
It enables navigation to waypoints that are not located at actual VOR or DME stations, allowing more direct routes and flexible routing in instrument conditions.
Intuition Check
Do not read “computer” here as a laptop or general-purpose device. In this context, it means a built-in navigation calculating unit carried in the aircraft.
Example Sentence 1
The airborne computer uses the selected VOR radial and DME distance to calculate the aircraft's position relative to the waypoint.
Example Sentence 2
During the approach, the airborne computer continuously updated the aircraft's position using nearby VOR and DME stations.