Tactical Air Navigation System referred to by the acronym “TACAN” is a navigation system used by military aircraft. TACAN provides the user with bearing and distance (slant-range) to a ground or ship-borne station.
TACAN is a more accurate version of the [VHF omnidirectional range]/[distance measuring equipment] (VOR/DME) system that provides bearing and range information for civil aviation.
It operates in the frequency band 960-1215 MHz. The bearing unit of TACAN is more accurate than a standard VOR since it makes use of a two frequency principle, with 15 Hz and 135 Hz components.
It should provide a ninefold increase in accuracy compared to a VOR but operational use has shown only a ±3 fold increase(theoretically). TACAN stations can provide distance up to 390NM. Accuracy of the 135 Hz azimuth component is ±1° or ±63 m at 3.47 km. Accuracy of the DME portion is 926 m (±0.5 nautical mile) or 3 percent of slant range distance, whichever is greater – see FAA 9840.1 1982.