Definition
A ground-based navigation facility that combines a non-directional beacon (NDB), which transmits a low- or medium-frequency signal a pilot can home to using an automatic direction finder (ADF), with collocated distance measuring equipment (DME) that provides slant-range distance from the station to the aircraft.
Plain English
A navigation station that does two jobs at once: it sends out a radio beacon a pilot can fly toward, and it also tells the aircraft how far away it is from the station.
Context Anchor
Seen in NOTAMs, FAA abbreviation lists, and navigation aid information when checking whether a ground-based navigation station is available or out of service.
Derivation
The 'H' comes from the ICAO classification letter for a non-directional beacon (high-powered homing facility). 'DME' stands for distance measuring equipment. So HDME literally reads as 'homing beacon plus distance gear.'
Why Pilots Care
Combines two navigation functions in one facility, reducing the need to cross-reference separate NDB and DME stations during instrument flight.
Example Sentence 1
The approach uses an HDME, so the pilot tracks inbound on the ADF needle while crosschecking distance from the DME readout.
Example Sentence 2
HDME facilities allow a single tuned frequency to supply bearing and distance for an instrument approach.