Definition
Instrument approach procedures based on area navigation that uses a VOR station paired with co-located DME equipment as the navigation reference. The aircraft's RNAV system computes its position from the VOR's bearing and the DME's distance, allowing the pilot to fly a course to a waypoint that is not located directly over a ground-based navaid. These approaches are an older form of RNAV and are gradually being replaced by GPS-based RNAV (GPS) and RNAV (RNP) procedures.
Plain English
An approach where the aircraft figures out its position by combining a direction from a VOR station with a distance from a DME station, then flies a path to imaginary points in space rather than directly over the station itself.
Context Anchor
Seen when briefing older RNAV approach procedures and checking whether the aircraft’s installed navigation equipment is approved to fly that specific approach.
Derivation
RNAV stands for area navigation, meaning navigation along any chosen path within the coverage of ground or space-based navaids, rather than only directly to or from a station. The 'VOR/DME' part names the two ground stations supplying the bearing and distance the RNAV computer uses to calculate position.
Why Pilots Care
They allow aircraft without GPS or inertial navigation to fly more flexible approaches than traditional ground-based procedures.
Grounding Statement
Picture the navigator using one known ground point, plus your direction and distance from it, to draw your position and keep you on the published approach path.
Intuition Check
“Based” does not mean the approach is only loosely related to VOR/DME. It means the RNAV guidance depends on VOR/DME information unless another authorized navigation method is specifically allowed.
Example Sentence 1
Before filing, the crew confirmed their avionics could fly a VOR/DME based RNAV approach, since the destination did not have a GPS overlay published.
Example Sentence 2
Before GPS, many airports published VOR/DME based RNAV approaches to provide direct routing to the final approach course.