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2025-02-02 14:20本頁面
【正文】 tabase contains the elements from which the flight plan is constructed. These are defined via the ARINC 424 standard. The navigation database (NDB) is normally updated every 28 days, in order to ensure that its contents are current. Each FMS contains only a subset of the ARINC data, relevant to the capabilities of the FMS.The NDB contains all of the information required for building a flight plan and information relevant to it. These includeWaypoints, Airways (highways in the sky) Radio navigation aids including DME (Distance Measuring Encoders), VOR (VHF Omnidirectional Range) NDB (Nondirectional beacons) Airports Runways Standard Instrument Departure (SID) Standard Terminal Arrival (STAR) Holding patterns And a variety of related and often installation specific information [edit] Flight PlanThe flight plan is generally determined on the ground, before departure either by the pilot for smaller aircraft or a professional dispatcher for airliners. It is entered into the FMS either by typing it in, selecting it from a saved library of mon routes or (Company Routes) or via a datalink with the airline dispatch center.During preflight other information relevant to managing the flight plan is entered. This can include performance information such as gross weight, fuel weight and center of gravity. It will include altitudes including the initial cruise altitude. For aircraft that do not have a GPS, the initial position is also required.The pilot uses the FMS to modify the flight plan, in flight for a variety of reasons. Significant engineering design minimizes the keystrokes in order to minimize pilot workload in flight and eliminate any confusing information (Hazardously Misleading Information). The FMS also sends the flight plan information for display on the Navigation Display (ND) of the flight deck instruments (EFIS). The flight plan generally appears as a magenta line, with other airports, radio aids and waypoints displayed.Special flight plans, often for tactical requirements including search patterns, rendezvous’, inflight refueling tanker orbits, calculated air release points (CARP) for accurate parachute jumps are just a few of the special flight plans some FMS can calculate.[edit] Position DeterminationOnce in flight, a principal task of the FMS is to determine the aircraft39。 Scanning DME (Distance measuring equipment) that check the distances from five different DME stations simultaneously in order to determine one position every 10 seconds or so. VOR’s (VHF Omnidirectional Radio Range) that supply both distance and bearing. With two VOR stations the aircraft position can be determined, but the accuracy is limited. Inertial Reference Systems (IRS) use ring laser gyros in order to calculate the aircraft position. They are highly accurate and independent of outside sources. Airliners use the weighted average of three independent IRS to determine the “triple mixed IRS” position. The FMS constantly crosschecks the various sensors and determines a single aircraft position and accuracy. The accuracy is described as the Actual Navigation Performance (ANP) a circle that the aircraft can be anywhere within measured as the diameter in nautical miles. Modern airspace has a set Required Navigation Performance (RNP). The aircraft must have its ANP less than its RNP in order to operate in certain highlevel airspace.[edit] GuidanceGiven the flight plan and the aircraft
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