VOR/DME

VOR/DME
Name	VOR/DME
Caption	VOR/DME ground facility schematic
Type	aviation navigation aid
Invented	mid-20th century
Inventor	Edward G. Scheinman
Country	International

VOR/DME

VOR/DME is a combined ground-based aeronautical radio navigation system used worldwide for en route and terminal operations. It integrates a Very High Frequency Omnidirectional Range station with a Distance Measuring Equipment transponder to provide radial bearing and slant distance to aircraft. Operators and regulators such as Federal Aviation Administration, International Civil Aviation Organization, Eurocontrol, Civil Aviation Authority (United Kingdom), and Airservices Australia have overseen siting and procedures for the system.

Overview

The system pairs a VHF Very High Frequency omnidirectional azimuth transmitter with a UHF Ultra High Frequency interrogator/responder for distance measurement. Primary users include operators flying between reporting points near aerodromes such as Heathrow Airport, John F. Kennedy International Airport, Sydney Airport, Tokyo Haneda Airport, and Dubai International Airport. Military organizations like the United States Air Force, Royal Air Force, and Indian Air Force have also used VOR/DME for tactical navigation. Manufacturers and suppliers include firms such as Honeywell International Inc., Thales Group, Raytheon Technologies, Collins Aerospace, and Leonardo S.p.A. for ground and airborne equipment.

Technical Description

A VOR provides azimuth information by transmitting a reference phase and a variable phase on VHF frequencies between 108.00 and 117.95 MHz. The DME component operates in the 960–1215 MHz band using pulse-pair interrogation and replies to compute slant range. Airborne receivers made by Garmin, BendixKing, Universal Avionics, Rockwell Collins, and Avidyne decode VHF bearings and UHF distance data. Signal processing relies on phase comparison and time-of-flight measurement techniques developed in parallel to work by researchers associated with Bell Labs, MIT Radiation Laboratory, National Aeronautics and Space Administration, and Institute of Navigation. Antenna farms sited at locations including Mount Wilson (California), Table Mountain (Cape Town), and Chilbolton Observatory ensure line-of-sight propagation.

Navigation and Procedures

Pilots use VOR/DME for route following on airways such as Victor airways, Jet routes (United States), and for instrument approaches including VOR/DME approach procedures at aerodromes like Los Angeles International Airport, Frankfurt Airport, and Chicago O'Hare International Airport. Flight crews plan using charts from Jeppesen, Federal Aviation Administration Aeronautical Information Services, Eurocontrol Aeronautical Information Publications, and national NOTAM systems like AIS Australia. Integration with avionics and flight management systems by vendors such as Honeywell, Rockwell Collins, and Thales allows coupling to autopilots during terminal procedures and holds depicted in publications like Instrument Flying Handbook (FAA) and ICAO Annex 10.

Installation and Maintenance

Siting and frequency coordination require coordination among authorities such as ICAO, Federal Communications Commission, Ofcom, and regional air navigation service providers including NAV CANADA and NATS (air traffic control). Installation projects have involved contractors like BAE Systems, Siemens, and Alenia Aeronautica for civil and military airports including Hartsfield–Jackson Atlanta International Airport and Paris–Charles de Gaulle Airport. Maintenance regimes follow standards from ICAO Annex 14 and manufacturer recommendations from Thales, Raytheon, and Honeywell, with periodic flight inspection by organizations such as Flight Inspection Modernization Project teams within Eurocontrol and national flight inspection units.

Limitations and Accuracy

Accuracy is affected by line-of-sight restrictions, terrain shielding at sites near Rocky Mountains, Andes, and Himalayas, and slant range errors at low altitudes over large airport complexes like Denver International Airport. Multipath reflection near urban centers such as New York City, London, and Hong Kong can introduce bearing errors. DME accuracy degrades with geometry and high vertical distance, influencing operations at airfields such as Tenzing-Hillary Airport and Sana'a International Airport. Interference sources include adjacent frequency users coordinated via International Telecommunication Union and spurious emissions from transmitters made in facilities like Rovereto and Farnborough Airport testing centers.

History and Development

Early VOR concepts evolved from radio range and Lorenz beam systems used in the 1930s and during World War II by organizations such as Royal Air Force and United States Army Air Forces. Postwar standardization involved ICAO committees and manufacturers including RCA, Philips, and Westinghouse Electric Corporation. Developments in DME trace to work by MIT, Bell Laboratories, and later avionics companies such as Collins Radio Company and Garmin Ltd. that advanced airborne interrogators and transponders. Program deployments expanded with civil aviation growth at hubs like O'Hare, Frankfurt am Main Airport, and Changi Airport during the Jet Age.

Global Use and Decommissioning Programs

Many states continue to operate VOR/DME networks while implementing satellite navigation via Global Positioning System, Galileo (satellite navigation), GLONASS, and BeiDou Navigation Satellite System. Decommissioning programs have been undertaken by authorities including FAA, UK CAA, Nav Canada, and Airservices Australia as part of performance-based navigation rollouts such as NextGen and SESAR. Regions with dense terrain or limited satellite coverage, as in parts of Africa, South America, and Central Asia, still rely on VOR/DME infrastructure near airports like Jomo Kenyatta International Airport, El Dorado International Airport, and Almaty International Airport. The transition involves coordination with operators such as IATA, ICAO, and airline groups including International Air Transport Association to ensure continuity of service and safety.

Category:Aviation navigation systems