Definition
An operating mode of an RNAV system used during instrument approach procedures, in which the unit's course-deviation sensitivity is increased so that a small lateral deviation produces a larger needle deflection than in en route mode. In this mode the RNAV computer continues to display position relative to a defined waypoint, but with finer guidance suitable for final approach tracking.
Plain English
A setting on the RNAV unit that you switch to when flying an approach. It makes the course needle more sensitive, so the aircraft has to stay tighter to the centerline than during cruise.
Context Anchor
Seen on older VOR/DME RNAV units when selecting navigation guidance to a programmed waypoint, especially when setting up for an instrument approach or approach-like course guidance.
Derivation
RNAV stands for area navigation -- a method of navigating directly between any two points rather than only between ground stations. APPR is short for approach. The mode name simply tells the pilot the box is now configured for the approach phase.
Why Pilots Care
It enables approaches to airports that lack ILS or VOR coverage, expanding the number of usable runways in instrument conditions.
Intuition Check
APPR does not mean the equipment has cleared you to fly an approach or that the approach is automatically approved. Here it means the navigation unit is using its approach guidance setting.
Example Sentence 1
After crossing the initial approach fix, the pilot selected RNAV/APPR mode to obtain finer course guidance for the final segment.
Example Sentence 2
With RNAV/APPR mode armed, the autopilot captured the vertical path and began a continuous descent to the runway.