A tactical air navigation system
, commonly referred to by the acronym TACAN
, is a navigation
system used by military aircraft. It provides the user with bearing and distance (slant-range) to a ground or ship-borne station. It is a more accurate version of the VOR
system that provides bearing
information for civil aviation
. The DME
portion of the TACAN system is available for civil use; at VORTAC
facilities where a VOR is combined
with a TACAN, civil aircraft can receive VOR/DME readings.Aircraft equipped with TACAN avionics
can use this system for enroute navigation as well as non-precision approach
to landing fields. The space shuttle
is one such vehicle that was designed to use TACAN navigation (although it has since been upgraded with GPS
as a replacement).
The typical TACAN onboard user panel has control switches for setting the channel (corresponding to the desired surface station's assigned frequency), the operation mode for either Transmit/Receive (T/R, to get both bearing and range) or Receive Only (REC, to get bearing but not range). Capability was later upgraded to include an Air-to-Air mode (A/A) where two airborne users can get relative slant-range information. Depending on the installation, Air-to-Air mode may provide range, closure (relative velocity of the other unit), and bearing, though an air-to-air bearing is noticeably less precise than a ground-to-air bearing.
The TACAN navigation system is an evolution of......