757 Flight Crew Training Manual 机组训练手册(40)

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Non-normal procedures are performed using the standard non-normal checklist. ETOPS engine-out procedures may be different from standard non-normal procedures. Following engine failure the crew performs a modified “driftdown” procedure determined by the ETOPS route requirements. This procedure typically uses higher descent and cruise speeds, and a lower cruise altitude following engine failure. This permits the airplane to reach an alternate airport within the specific time limits authorized for that operator. These cruise speeds and altitudes are determined by the airline and approved by its regulatory agency and usually differ from the engine-out speeds provided by the FMC. The captain however, has the discretion to modify this speed if actual conditions following the diversion decision dictate such a change.
With an in-flight loss of both main AC busses, the hydraulic driven generator automatically powers essential electrical systems. In this case the total air temperature indicator is inoperative and Static Air Temperature (SAT) must be used to calculate performance. If the hydraulic driven generator is inoperative, the APU must be operating before entering the ETOPS phase of flight.
If an engine failure occurs and is accompanied by a loss of both main AC busses, the airplane may have to be retrimmed to compensate for the induced yaw. The rudder ratio changer is unpowered following a loss of both main AC busses.

A loss of main AC busses unpowers the fuel boost pumps. The system design normally precludes any fuel imbalance because fuel is drawn approximately equally from both wing tanks. In the unlikely event that an imbalance occurs, a deliberate sideslip may be used to raise the wing containing the heavier tank. This ensures that the fuel is drawn from the heavier tank to balance the load. This action may slightly decrease the range due to the increased sideslip drag.

Polar Operations
Refer to the FMC Polar Navigation section of the Operations Manual for specifics on FMC operation in polar regions and a description of the boundaries of the polar regions.
During preflight planning extremely cold air masses should be noted and cold fuel temperatures should be considered. See the Low Fuel Temperature section in this chapter for details regarding recommendations and crew actions.
Operators should establish a remote airport diversion plan to include supporting the airplane, passengers and crew. Airplane equipment and document needs to be considered:
. 
cold weather clothing to enable one or more crewmembers to exit the
airplane at a diversion airport with extreme cold conditions

. 
comprehensive instructions on securing the airplane for cold weather to
include draining water tanks, etc.

. 
diversion airport data to include airport diagrams, information on nearby
terrain and photographs (if available), emergency equipment availability,
etc.

. 
cold temperature altitude correction table.

Due to limited availability of alternate airports relative to other regions, special attention should be given to diversion planning including airport conditions and availability of compatible fuel. Crews should be prepared to operate in QFE and metric altitude where required. Expect changes in assigned cruising levels enroute since standard cruising levels vary by FIR. Some airports provide QNH upon request, even if their standard is QFE. Metric wind speed (m/sec) may be all that is available. A simple approximation: 1 m/sec = 2 knots. A feet to meters conversion chart may be useful for planning step climbs, converting minima, etc.
Use caution when using ADF and/or VOR raw data. ADF orientation (true or magnetic) is determined by the heading reference selected by the crew. VOR radials are displayed according to the orientation of the VOR station.

Communications should be handled according to the applicable enroute charts. Above 82 degrees N, SATCOM is unavailable. HF frequencies and HF SELCAL must be arranged by the flight crew prior to the end of SATCOM coverage. Routine company communications procedures should include flight following to enable immediate assistance during a diversion or other emergency.
Note: To use SATCOM on the ground, the IRUs/ADIRUs (as installed) must be aligned.
When navigating in the polar regions, magnetic heading should be considered unreliable or totally useless for navigation. Magnetic variations typically are extreme, often are not constant at the same point and change rapidly as airplane position changes. Ensure the computer flight plan shows true tracks and true headings. Grid headings may also be used as a reference for those airplanes equipped with grid heading indicators although no airplane systems use grid heading. For some high latitude airports, grid headings are shown on the instrument approach procedures. Note that unmapped areas in the GPWS terrain data base display as magenta dots on the map, regardless of the airplane altitude.
　
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