时间：2011-04-18 00:50来源：蓝天飞行翻译 作者：航空 点击：次
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1. The minimum vectoring altitude in each sector provides 1,000 feet above the highest obstacle in nonmountainous areas and 2,000 feet above the highest obstacle in designated mountainous areas. Where lower MVAs are required in designated mountainous areas to achieve compatibility with terminal routes or to permit vectoring to an IAP, 1,000 feet of obstacle clearance may be authorized with the use of Airport Surveillance Radar (ASR). The minimum vectoring altitude will provide at least 300 feet above the floor of controlled airspace. NOTE. OROCA is an off.route altitude which provides obstruc-tion clearance with a 1,000 foot buffer in nonmountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the U.S. This altitude may not provide signal coverage from ground.based navigational aids, air traffic control radar, or communications coverage. 2. Because of differences in the areas consid-ered for MVA, and those applied to other minimum altitudes, and the ability to isolate specific obstacles, some MVAs may be lower than the nonradar Minimum En Route Altitudes (MEAs), Minimum Obstruction Clearance Altitudes (MOCAs) or other minimum altitudes depicted on charts for a given location. While being radar vectored, IFR altitude assignments by ATC will be at or above MVA. f. Visual Descent Points (VDPs) are being incorporated in nonprecision approach procedures. The VDP is a defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided visual reference required by 14 CFR Section 91.175(c)(3) is established. The VDP will normally be identified by DME on VOR and LOC Arrival Procedures 5.4.17 procedures and by along.track distance to the next waypoint for RNAV procedures. The VDP is identified on the profile view of the approach chart by the symbol: V. 1.VDPs are intended to provide additional guidance where they are implemented. No special technique is required to fly a procedure with a VDP. The pilot should not descend below the MDA prior to reaching the VDP and acquiring the necessary visual reference. 2.Pilots not equipped to receive the VDP should fly the approach procedure as though no VDP had been provided. g. Visual Segment of a Published Instrument Approach Procedure. Instrument procedures de-signers perform a visual area obstruction evaluation off the approach end of each runway authorized for instrument landing, straight.in, or circling. Restric-tions to instrument operations are imposed if penetrations of the obstruction clearance surfaces exist. These restrictions vary based on the severity of the penetrations, and may include increasing required visibility, denying VDPs, prohibiting night instru-ment operations to the runway, and/or provide a “Fly Visual” option to the landing surface. 1.In isolated cases, due to procedure design peculiarities, an IAP may contain a published visual flight path. These procedures are annotated “Fly Visual to Airport” or “Fly Visual.” A dashed arrow indicating the visual flight path will be included in the profile and plan views with an approximate heading and distance to the end of the runway. The depicted ground track associated with the visual segment should be flown as a “DR” course. When executing the visual segment, the flight visibility must not be less than that prescribed in the IAP, the pilot must re-main clear of clouds and proceed to the airport maintaining visual contact with the ground. Altitude on the visual flight path is at the discretion of the pilot. 2.Since missed approach obstacle clearance is assured only if the missed approach is commenced at the published MAP or above the DA/MDA, the pilot should have preplanned climb out options based on aircraft performance and terrain features. Obstacle clearance is the sole responsibility of the pilot when the approach is continued beyond the MAP. NOTE. The FAA Administrator retains the authority to approve instrument approach procedures where the pilot may not necessarily have one of the visual references specified in CFR 14, part 91.175 and related rules. It is not a function of procedure design to ensure compliance with part 91.175. The annotation “Fly Visual to Airport” provides relief from part 91.175 requirements that the pilot have dis-tinctly visible and identifiable visual references prior to descent below MDA/DA. h.Charting of Close in Obstacles on Instru-ment Procedure Charts. Obstacles that are close to the airport may be depicted in either the planview of the instrument approach chart or the airport sketch. Obstacles are charted in only one of the areas, based on space available and distance from the runway. These obstacles could be in the visual segment of the instrument approach procedure. On nonprecision approaches, these obstacles should be considered when determining where to begin descent from the MDA (see “Pilot Operational Considerations When Flying Nonprecision Approaches” in this paragraph). i.Vertical Descent Angle (VDA) on Nonpreci-sion Approaches. FAA policy is to publish VDAs on all nonprecision approaches. Published along with VDA is the threshold crossing height (TCH) that was used to compute the angle. The descent angle may be computed from either the final approach fix (FAF), or a stepdown fix, to the runway threshold at the published TCH. A stepdown fix is only used as the start point when an angle computed from the FAF would place the aircraft below the stepdown fix altitude. The descent angle and TCH information are charted on the profile view of the instrument approach chart following the fix the angle was based on. The optimum descent angle is 3.00 degrees; and whenever possible the approach will be designed using this angle. 1. The VDA provides the pilot with information not previously available on nonprecision approaches. It provides a means for the pilot to establish a stabilized descent from the FAF or stepdown fix to the MDA. Stabilized descent is a key factor in the reduction of controlled flight into terrain (CFIT) incidents. However, pilots should be aware that the published angle is for information only . it is strictly advisory in nature. There is no implicit additional obstacle protection below the MDA. Pilots must still respect the published minimum descent altitude (MDA) unless the visual cues stated 14 CFR Section 91.175 are present and they can visually Arrival Procedures 5.4.18 acquire and avoid obstacles once below the MDA. The presence of a VDA does not guarantee obstacle protection in the visual segment and does not change any of the requirements for flying a nonprecision approach. |
