The theoretical and technical principles of operation of ILS equipment are discussed in depth in AFMAN 11-217V3.Д¤.6.1. Additional information on DME is available in AFMAN 11-217V3. The time required for the round trip of this signal exchange is measured in the airborne DME unit and is displayed to the pilot as a distance in nautical miles from the aircraft to the ground station. The ground station then transmits paired pulses back to the aircraft at the same pulse spacing but on a different frequency. Additional information on VORTACs is available in AFMAN 11-217V3.ДME operation utilizes paired pulses transmitted from the aircraft to a ground station at a specific spacing. Both components of a VORTAC operate simultaneously and provide the three services at all times. VHF Omni-Directional Range/Tactical Air Navigation (VORTAC).ДЄ VORTAC is a unified navigation aid consisting of two components, VOR and TACAN, which provides three individual services: VOR azimuth, TACAN azimuth, and TACAN distance (DME) from one site. TACAN components and operation are discussed in depth in AFMAN 11-217V3.Д¤.4. The theoretical and technical principles of operation of TACAN equipment differ from those of VOR however, the end result, as far as reading the cockpit display is concerned, is the same. The theoretical and technical principles of operation of VOR equipment are discussed in depth in AFMAN 11-217V3. The problem may be the ground station and not the aircraft equipment. Advise ATC of any problems receiving NAVAIDs. Discontinue use of any suspect navigation aid and confirm aircraft position with radar (ground or airborne) or other equipment. The pilot will check notices to airmen (NOTAM) and flight information publication (FLIP) before flight for possible malfunctions or limitations to navigation aids.Д¤.1.5.

Never overfly an estimated time of arrival (ETA) without a careful crosscheck of navigation aids and ground checkpoints.Д¤.1.4. Use all suitable navigation equipment aboard the aircraft and crosscheck heading and bearing information.Д¤.1.3. The pilot will check the identification of any navigation aid and monitor it during flight IAW Chapter 7 of this manual.Д¤.1.2. Although operating principles and cockpit displays will vary among navigation systems, there are several precautionary actions that must be taken to prevent in-flight use of erroneous navigation signals:Д¤.1.1. Various types of navigation aids are in use today, each serving a special purpose.

Localizer directional aid