A precision approach is an approach where electronic glideslope information is available. On approaches which incorporate a DA(H), the aircraft is descended on the glideslope and a decision to either land or execute a missed approach must occur at or before DA(H). A decision to continue the approach below DA(H) requires adequate visual references as per this chapter, and the aircraft must be in a position to make a safe landing.
Depending on weather conditions, an ILS can be accomplished with raw data, with the flight director, or with the autopilot approach coupler.
ILS approaches in weather conditions above 2400 RVR may be hand flown or flown with the autopilot approach coupler at pilot’s discretion. The flight director should be used in either case.
Note: If weather conditions are below 4000 RVR or 3/4 mile visibility, a flight director must be used or a coupled approach must be made.
ILS approaches in weather conditions reported or anticipated to be at or below 2400 RVR should be flown using Continental Airlines monitored approach procedures. If the RVR is 2400 feet or less, the flight crew will brief the category of approach having the lowest minimum for which the aircraft, ILS facility, and flight crew are capable of conducting, even if the latest reported weather would permit a category of approach that has a higher minimum. If the crew has been cleared for an approach using standard ILS procedures and weather conditions subsequently decrease below 2400 RVR, the aircraft may continue as briefed at Captain’s discretion. Attempting to establish monitored approach procedures and configuration once the approach has commenced is not recommended.
ILS Mode FGS Operation
FD The FD will provide guidance commands.
AP The AP will control the airplane to automatically capture and track the localizer and glideslope.
ILS mode should be armed when the aircraft is on an intercept heading to the final approach course.
Note: If correct ILS/LOC inbound course has not been set, and a large discrepancy exists between the actual LOC inbound course and the selected course, the flight guidance system will not attempt to complete the course intercept; the airplane will fly through the localizer, wings level. In that case, LOC CAP may be annunciated and G/S TRK could occur, causing the airplane to begin to descend. Upon failing to attain LOC TRK and after exiting the localizer beam, the autopilot will disconnect and flight guidance will revert to HDG HLD/VERT SPD.
LOC CAP is displayed as the DFGS provides commands to turn on course and maneuver to localizer beam centerline. When established on localizer beam center line, LOC TRK is displayed.
The DFGS will capture and track the glideslope independent of localizer capture. Glideslope capture will begin immediately if capture conditions are satisfied at the time of ILS mode selection. The glideslope may be intercepted from above using a vertical path mode that provides a rate of descent (1000 to 1500 FPM) that is greater than the glideslope, or intercepted from below the glideslope using altitude hold mode.
G/S CAP is displayed as the DFGS provides commands to maneuver to glideslope beam center by establishing the airplane on a rate of descent that coincides with the glideslope. When established on glideslope beam centerline, G/S TRK is displayed.
To disarm the ILS mode before capture:
.
Push HDG knob in to engage HDG HLD mode.
To disarm ILS mode after LOC or G/S Capture:
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Select another roll mode - the ILS mode will disengage and the pitch mode will revert to VERT SPD.
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Select another pitch mode - the ILS mode will disengage and the roll mode will revert to HDG HLD.
FMA Displays During ILS Mode Approach
1.
SPD ILS HDG VERT
250 ALT SEL SPD
Airplane is descending on intercept heading for localizer with ILS and altitude preselect armed.
2.
SPD ILS LOC ALT
165 CAP CAP
Localizer and altitude (preselect) capture have been initiated. Airplane is turning onto localizer and leveling out on approach altitude.
3.
SPD ILS LOC ALT
165 TRK HLD
Localizer and altitude capture have been completed. The airplane is tracking the localizer on a preselected altitude to intercept the glideslope.
4.
SPD ILS LOC G/S
165 TRK CAP
Glideslope capture has been initiated. The airplane is tracking the localizer while establishing a rate of descent to coincid with the glideslope. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：MD-80 Flight Manual 麦道80飞行手册 2(12)
