Tactical air navigation system
Tactical Air Navigation ( TACAN, English for tactical air navigation ) is a military beacon that the civil use VOR / DME is very similar. TACAN provides range and azimuth information ( polar coordinates) from a single ground station.
The TACAN and DME systems are interoperable, the combinations TACAN-Bordgerät/DME-Bodenstation, DME-Bordgerät/TACAN-Bodenstation and DME-Bordgerät/DME-Bodenstation only provide distance information; only the combination TACAN-Bordgerät/TACAN-Bodenstation provides both distance and azimuth information.
The equipment combination consisting of VOR and TACAN, is used in the Air Force of the Armed Forces under the name VORTAC. Civil aircraft get azimuth information from the VOR portion of the VORTAC and distance information from compatible DME TACAN part; Military aircraft get azimuth and distance information from the TACAN ( without using the VOR). TACAN equipment are also used on military ships to navigation, for example. Board helicopters back to the mother ship, to allow in bad weather.
Operation
TACAN beacon operating in the frequency range 962-1213 MHz ( divided into 126 X and 126 Y channels), which is allocated to the aeronautical radionavigation service on primary use. The direction information is always relative to magnetic north when TACAN (see VOR). The corresponding instrument display always shows the right-handed angle from north to a line aircraft - ground station.
While the directional information is any number of aircraft simultaneously available, only a maximum of 100 aircraft may be operated simultaneously for distance measurement, while always maintaining the 100 strongest signals have priority. Distances supplied by the TACAN, however, are basically slant ranges, ie the direct distance between the aircraft and the ground station. Determining the exact distance is only possible if the amount is known about the background or the angle of elevation. The TACAN operates in quasi -sight up to a distance of 390 nautical miles.
Unlike the VOR to a TACAN station can also be located on board a military aircraft and other example is used in tank approaches.
The pointing by other aircraft but is less accurate than to a ground station, as of most aircraft only the 15 Hz sine wave can be sent which is thus an accuracy / error of about 3 ° to 5 ° moves to itself. In a TACAN ground station of the 15 Hz sine wave is additionally modulated by 135 Hz amplitude modulation, thus the 15 Hz are the coarse information and the 135 Hz based the fine information of the direction to the station to magnetic north. In addition, unlike BEFORE the main reference pulse ( MRB ) is only emitted when the VOR shows eastwards, every 40 degrees will be sent a by- reference pulse (ARB ). The MRB is for the plant important insofar as it marks the starting point of the angle measurement to the next positive zero crossing of the 15 Hz oscillation. Thus, for example, results in an MRB pulse at 180 ° to the next positive zero crossing of the sine wave 15 Hz (360 ° ) is an angle of 180 °, so the station is located to the south. In MRB 90 ° ( neg ) = 90 ° angle to the next heading. Zero crossing = station eastwards At MRB 90 ° ( pos.) = angle of 270 ° to the next heading. Zero crossing = station westwards In MRB 0 ° = 0 ° angle station northbound
Frequency availability
On the part of the spectrum management has been declared for the TACAN frequency availability with restrictions. Thus, the airborne use in German airspace and the use on marine vessels in the German territorial waters example, are not permitted.
TACAN stations in Germany
The following frequency channels are assigned to coordinated and Europe for the TACAN sites in question: