Approach Preparations for using VNAV
Select the approach procedure from the ARRIVALS page of the FMC. Tune and identify appropriate navaids. Do not manually build the approach or add waypoints to the procedure. If additional waypoint references are desired, use the FIX page. To enable proper LNAV waypoint sequencing, select a straight-in intercept course to the FAF when being radar vectored to final approach. Verify/enter the appropriate RNP and set the DA(H) or MDA(H) using the baro minimums selector. If required to use MDA(H) for the approach minimum altitude, the barometric minimums selector should be set at MDA + 50 feet to ensure that if a missed approach is initiated, descent below the MDA(H) does not occur during the missed approach.
Note: The approach RNP is not displayed until the first waypoint of the approach is sequenced unless the pilot manually enters an RNP.
Final Approach using VNAV
Approaching intercept heading, select flaps 5 and ensure LNAV or other appropriate roll mode is armed or engaged. Approaching the FAF (approximately 2 NM), select gear down and flaps 20 and adjust speed. Set the DA(H) or MDA(H) in the MCP altitude window, select VNAV, and ensure VNAV PTH and appropriate roll mode is annunciated. Use VNAV speed intervention to control speed.
Note: If desired altitude is not at an even 100 foot increment, set the MCP altitude to the nearest 100 ft. increment below the altitude constraint or MDA(H).
Just prior to FAF, select landing flaps, reduce to final approach speed and complete the Landing checklist. If the charted FAF is too close to the runway to permit a stabilized approach, consider establishing final approach pitch mode and configuring for approach and landing earlier than specified in the Operations Manual procedure.
With the MCP altitude set to DA(H) or MDA(H) and the airplane stabilized on the final approach path, the map altitude range arc assists in determining the visual descent point (VDP). As soon as the airplane is at least 300 feet below the missed approach altitude and stabilized on final approach in VNAV PTH, set the MCP altitude to the missed approach altitude. VNAV path deviation indications on the map display assist in monitoring the vertical profile. The autopilot tracks the path in VNAV PTH resulting in arrival at, or near, the visual descent point by the DA(H) or MDA(H).
Minimum Descent Altitude (MDA(H))/Decision Altitude (DA(H))
When specifically authorized by the instrument procedure and regulatory authority, approaches may be flown to the following minima:
.
a published VNAV DA(H)
.
a published MDA(H) used as a decision altitude
When either of the above minima are not specifically authorized, use the MDA(H) specified for the instrument procedure.
When reaching the DA(H) or MDA(H), be prepared to disengage the autopilot, disconnect the autothrottle and land or execute an immediate go-around.
Note: If using an MDA(H), initiating a missed approach approximately 50 feet
above MDA(H) may be necessary to avoid descending below the MDA(H)
during the missed approach, if required for the procedure or by the
regulatory authority.
The pilot not flying should expand the instrument scan to include outside visual cues when approaching DA(H) or MDA(H). Do not continue the approach below DA(H) or MDA(H) unless the airplane is in a position from which a normal approach to the runway of intended landing can be made and suitable visual reference can be maintained. Upon arrival at DA(H) or MDA(H) or any time thereafter, if any of the above requirements are not met, immediately execute the missed approach procedure.
When suitable visual reference is established, maintain the descent path to the flare. Do not descend below the visual glide path. While VNAV PTH guidance may still be used as a reference once the airplane is below DA(H) or MDA(H), the primary means of approach guidance is visual.
Note: VNAV path guidance transitions to level flight once the missed approach fix is passed.
Simulated Instrument Approach Using VNAV
To maintain proficiency, crews may practice instrument approach using VNAV procedures while flying ILS approaches as follows:
.
ensure the ILS is tuned and identified and the ILS raw data is monitored
throughout the approach
.
track the localizer using LOC or LNAV as the roll mode
.
use VNAV as the pitch mode to track the GP angle. The charted GP angle
normally coincides with the ILS glide slope angle
.
disengage autopilot by the minimum altitude specified in the limitations
chapter of the Operations Manual.
Note: Limit the use of the above technique to VMC weather conditions.
In ambient temperature conditions warmer than ISA standard, the airplane may remain slightly high relative to the ILS glide slope, and in temperatures colder than ISA standard, the airplane may remain slightly lower than the ILS glide slope. Discontinue use of this technique and manually track the localizer and glide slope if localizer or glide slope deviations become unacceptable. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：757 Flight Crew Training Manual 机组训练手册(61)
