AIM COM 4.7 Distance Measuring Equipment (DME)
Distance measuring equipment (DME) functions by means of two-way transmissions of signals between the aircraft and the DME site. Paired pulses at a specific spacing are sent out from the aircraft and are received by the ground station. The ground station then transmits paired pulses back to the aircraft on a different frequency. The time required for this signal exchange is measured in the airborne DME unit and is translated into distance (nautical mile [NM]) from the aircraft to the ground station. Distance information received from DME is slant range distance and not actual horizontal distance. Accuracy of the DME system is within ±0.5 NM or three percent of the distance, whichever is greater.
DME is collocated with most Canadian VHF omnidirectional range (VOR) installations (VOR/DME) and with many instrument landing system (ILS) and localizers (LOCs). In some cases, DME are also collocated with non-directional beacons (NDBs) to provide improved navigation capability.
The DME operates in the UHF band and therefore is limited to line-of-sight reception with a range similar to that of a VOR. The receiving equipment in most aircraft provide automatic DME selection through a coupled VOR/ILS receiver.
Distance information from a Tactical Air Navigation aid (TACAN) facility can be obtained by selecting the appropriate paired VOR frequency. (In that case, only DME information is being received; any apparent radial information must be ignored.)
The DME slant range error is the greatest when the airplane is at a high altitude close to or over the ground station. Moreover, slant range error also affects groundspeed and time-to-staion displays when you are close to the station.
AIM COM 4.8 TACTICAL AIR NAVIGATION (TACAN)
Tactical air navigation aid (TACAN) is a navigation aid (NAVAID) used primarily by the military for en route, non-precision approaches (NPAs) and other military applications. It provides azimuth in the form of radials and slant distance in nautical miles (NM) from the ground station. The system operates in the ultrahigh frequency (UHF) range with the frequencies identified by channel number.
TACAN users may obtain distance information from a distance measuring equipment (DME) that is paired with the VHF omnidirectional range (VOR). This TACAN paired channel number is published in the Canada Flight Supplement (CFS) for every VOR/DME facility.
CAUTION:
Only DME information is being received by the TACAN avionics. Any apparent radial information obtained through the TACAN avionics from a VOR/DME facility can only be false signals.
AIM COM 4.7 Distance Measuring Equipment (DME)
Distance measuring equipment (DME) functions by means of two-way transmissions of signals between the aircraft and the DME site. Paired pulses at a specific spacing are sent out from the aircraft and are received by the ground station. The ground station then transmits paired pulses back to the aircraft on a different frequency. The time required for this signal exchange is measured in the airborne DME unit and is translated into distance (nautical mile [NM]) from the aircraft to the ground station. Distance information received from DME is slant range distance and not actual horizontal distance. Accuracy of the DME system is within ±0.5 NM or three percent of the distance, whichever is greater.
DME is collocated with most Canadian VHF omnidirectional range (VOR) installations (VOR/DME) and with many instrument landing system (ILS) and localizers (LOCs). In some cases, DME are also collocated with non-directional beacons (NDBs) to provide improved navigation capability.
The DME operates in the UHF band and therefore is limited to line-of-sight reception with a range similar to that of a VOR. The receiving equipment in most aircraft provide automatic DME selection through a coupled VOR/ILS receiver.
Distance information from a Tactical Air Navigation aid (TACAN) facility can be obtained by selecting the appropriate paired VOR frequency. (In that case, only DME information is being received; any apparent radial information must be ignored.)
The DME slant range error is the greatest when the airplane is at a high altitude close to or over the ground station. Moreover, slant range error also affects groundspeed and time-to-staion displays when you are close to the station.
AIM COM 4.8 TACTICAL AIR NAVIGATION (TACAN)
Tactical air navigation aid (TACAN) is a navigation aid (NAVAID) used primarily by the military for en route, non-precision approaches (NPAs) and other military applications. It provides azimuth in the form of radials and slant distance in nautical miles (NM) from the ground station. The system operates in the ultrahigh frequency (UHF) range with the frequencies identified by channel number.
TACAN users may obtain distance information from a distance measuring equipment (DME) that is paired with the VHF omnidirectional range (VOR). This TACAN paired channel number is published in the Canada Flight Supplement (CFS) for every VOR/DME facility.
CAUTION:
Only DME information is being received by the TACAN avionics. Any apparent radial information obtained through the TACAN avionics from a VOR/DME facility can only be false signals.