时间：2011-04-18 00:52来源：蓝天飞行翻译 作者：航空 点击：次
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DH [ICAO]. (See ICAO Term DECISION ALTITUDE/ DECISION HEIGHT.)DIGITAL-AUTOMATIC TERMINAL INFORMA-TION SERVICE (D-ATIS). The service provides text messages to aircraft, airlines, and other users outside the standard reception range of conventional ATIS via landline and data link communications to the cockpit. Also, the service provides a computer. synthesized voice message that can be transmitted to all aircraft within range of existing transmitters. The Terminal Data Link System (TDLS) D-ATIS application uses weather inputs from local automated weather sources or manually entered meteorological data together with preprogrammed menus to provide standard information to users. Airports with D-ATIS capability are listed in the Airport/Facility Directory. DIGITAL TARGET. A computer.generated symbol representing an aircraft’s position, based on a primary return or radar beacon reply, shown on a digital display. DIGITAL TERMINAL AUTOMATION SYSTEM (DTAS). A system where digital radar and beacon data is presented on digital displays and the operational program monitors the system perfor-mance on a real.time basis. DIGITIZED TARGET. A computer.generated indication shown on an analog radar display resulting from a primary radar return or a radar beacon reply. DIRECT. Straight line flight between two naviga-tional aids, fixes, points, or any combination thereof. When used by pilots in describing off-airway routes, points defining direct route segments become compulsory reporting points unless the aircraft is under radar contact. DIRECT ALTITUDE AND IDENTITY READ-OUT. The DAIR System is a modification to the PCG D.2 AN/TPX-42 Interrogator System. The Navy has two adaptations of the DAIR System-Carrier Air Traffic Control Direct Altitude and Identification Readout System for Aircraft Carriers and Radar Air Traffic Control Facility Direct Altitude and Identity Readout System for land-based terminal operations. The DAIR detects, tracks, and predicts secondary radar aircraft targets. Targets are displayed by means of computer-generated symbols and alphanumeric characters depicting flight identification, altitude, ground speed, and flight plan data. The DAIR System is capable of interfacing with ARTCCs. DIRECTION FINDER. A radio receiver equipped with a directional sensing antenna used to take bearings on a radio transmitter. Specialized radio direction finders are used in aircraft as air navigation aids. Others are ground-based, primarily to obtain a “fix” on a pilot requesting orientation assistance or to locate downed aircraft. A location “fix” is established by the intersection of two or more bearing lines plotted on a navigational chart using either two separately located Direction Finders to obtain a fix on an aircraft or by a pilot plotting the bearing indications of his/her DF on two separately located ground-based transmitters, both of which can be identified on his/her chart. UDFs receive signals in the ultra high frequency radio broadcast band; VDFs in the very high frequency band; and UVDFs in both bands. ATC provides DF service at those air traffic control towers and flight service stations listed in the Airport/Facility Directory and the DOD FLIP IFR En Route Supplement. (See DF FIX.)(See DF GUIDANCE.)DIRECTLY BEHIND. An aircraft is considered to be operating directly behind when it is following the actual flight path of the lead aircraft over the surface of the earth except when applying wake turbulence separation criteria. DISCRETE BEACON CODE. (See DISCRETE CODE.)DISCRETE CODE. As used in the Air Traffic Control Radar Beacon System (ATCRBS), any one of the 4096 selectable Mode 3/A aircraft transponder codes except those ending in zero zero; e.g., discrete codes: 0010, 1201, 2317, 7777; nondiscrete codes: 0100, 1200, 7700. Nondiscrete codes are normally reserved for radar facilities that are not equipped with Pilot/Controller Glossary discrete decoding capability and for other purposes such as emergencies (7700), VFR aircraft (1200), etc. (See RADAR.)(Refer to AIM.)DISCRETE FREQUENCY. A separate radio frequency for use in direct pilot-controller commu-nications in air traffic control which reduces frequency congestion by controlling the number of aircraft operating on a particular frequency at one time. Discrete frequencies are normally designated for each control sector in en route/terminal ATC facilities. Discrete frequencies are listed in the Airport/Facility Directory and the DOD FLIP IFR En Route Supplement. (See CONTROL SECTOR.)DISPLACED THRESHOLD. A threshold that is located at a point on the runway other than the designated beginning of the runway. (See THRESHOLD.)(Refer to AIM.)DISTANCE MEASURING EQUIPMENT. Equip-ment (airborne and ground) used to measure, in nautical miles, the slant range distance of an aircraft from the DME navigational aid. (See MICROWAVE LANDING SYSTEM.)(See TACAN.)(See VORTAC.)DISTRESS. A condition of being threatened by serious and/or imminent danger and of requiring immediate assistance. DIVE BRAKES. (See SPEED BRAKES.)DIVERSE VECTOR AREA. In a radar environ-ment, that area in which a prescribed departure route is not required as the only suitable route to avoid obstacles. The area in which random radar vectors below the MVA/MIA, established in accordance with the TERPS criteria for diverse departures, obstacles and terrain avoidance, may be issued to departing aircraft. DIVERSION (DVRSN). Flights that are required to land at other than their original destination for reasons beyond the control of the pilot/company, e.g. periods of significant weather. DME. (See DISTANCE MEASURING EQUIPMENT.)PCG D.3 DME FIX. A geographical position determined by reference to a navigational aid which provides distance and azimuth information. It is defined by a specific distance in nautical miles and a radial, azimuth, or course (i.e., localizer) in degrees magnetic from that aid. (See DISTANCE MEASURING EQUIPMENT.)(See FIX.)(See MICROWAVE LANDING SYSTEM.)DME SEPARATION. Spacing of aircraft in terms of distances (nautical miles) determined by reference to distance measuring equipment (DME). |
