737机组训练手册 Flight Crew Training Manual FCTM(29)

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Note:  Monitor the nose gear track closely, as it will leave the pavement in the turn before the main gear.
Approach the edge of the taxi surface at a shallow angle until the outboard side of the main gear wheels are near the edge. The main gear are just inside the engine nacelles. Maneuver to keep the engine nacelles over the prepared surfaces.
Note:  Painted runway markings are slippery when wet and may cause skidding of the nose gear during the turn.
Turning radius can be reduced by following a few specific taxi techniques. Taxi the airplane so that the main gear tires are close to the runway edge.This provides more runway surface to make the turn. Stop the airplane completely with the thrust at idle. Hold the nose wheel steering wheel to the maximum steering angle, release the brakes, then add thrust on the outboard engine. Only use the engine on the outboard side of the turn and maintain 5 to 10 knots during the turn to minimize turn radius. Light intermittent braking on the inside main gear helps decrease turn radius. Stopping the airplane in a turn is not recommended unless required to reduce the turn radius. As the airplane passes through 90° of turn, steer to place the main gear approximately on the runway centerline, then gradually reduce the nose wheel steering wheel input as required to align the airplane with the new direction of taxi. These actions result in a low speed turn and less runway being used. Wind, slope, runway or taxiway surface conditions, and center of gravity may also affect the turning radius.
The following diagrams show suggested airplane ground tracks for minimum radius 180° turns with various runway turnaround configurations. These ground tracks provide the best maneuver capability while providing the maximum runway length available for takeoff at the completion of the turn. However, this type of maneuvering is normally not required unless operating on runways less than 148 feet (45m) in width.

737 Flight Crew Training  Manual
Techniques when using a Circular Turnaround

Copyright . The Boeing Company. See title page for details.
2.10 FCT 737 (TM) October 31, 2006
737 Flight Crew Training  Manual
Techniques when using a Hammerhead Turnaround
Align airplane
near runway edge.
When abeam center of the turnaround, stop the airplane, apply full steering wheel, then add thrust to maintain 5 to 10 knots during the turn.
Note:  Follow turnaround steering guidance cues if available.
When turn completion is assured and main gear are on the runway centerline, steer toward runway centerline.
Use momentary application of insidebrakes, as needed.

737 Flight Crew Training  Manual
Techniques when using a Hammerhead Turnaround

10 knots during the turn.

Taxi - Adverse Weather
Taxi under adverse weather conditions requires more awareness of surface conditions.
Copyright . The Boeing Company. See title page for details.
2.12 FCT 737 (TM) October 31, 2006
737 Flight Crew Training  Manual
When taxiing on a slippery or contaminated surface, particularly with strong crosswinds, use reduced speeds. Use of differential engine thrust assists in maintaining airplane momentum through the turn. When nearing turn completion, placing both engines to idle thrust reduces the potential for nose gear skidding. Avoid using large nose wheel steering inputs to correct for skidding. Differential braking may be more effective than nose wheel steering on slippery or contaminated surfaces. If speed is excessive, reduce speed prior to initiating a turn.
Note:  A slippery surface is any surface where the braking capability is less than that on a dry surface. Therefore, a surface is considered “slippery” when it is wet or contaminated with ice, standing water, slush, snow or any other deposit that results in reduced braking capability.
During cold weather operations, nose gear steering should be exercised in both directions during taxi. This circulates warm hydraulic fluid through the steering cylinders and minimizes the steering lag caused by low temperatures. If icing conditions are present, use anti-ice as required by the FCOM.
During prolonged ground operations, periodic engine run-ups should be accomplished to minimize ice build-up. These engine run-ups should be performed as defined in the FCOM.
Engine exhaust may form ice on the ramp and takeoff areas of the runway, or blow snow or slush which may freeze on airplane surfaces. If the taxi route is through slush or standing water in low temperatures, or if precipitation is falling with temperatures below freezing, taxi with flaps up. Extended or prolonged taxi times in heavy snow may necessitate de-icing prior to takeoff.
Low Visibility
Pilots need a working knowledge of airport surface lighting, markings, and signs for low visibility taxi operations. Understanding the functions and procedures to be used with stop bar lights, ILS critical area markings, holding points, and low visibility taxi routes is essential to conducting safe operations. Many airports have special procedures for low visibility operations. For example, airports operating under FAA criteria with takeoff and landing minimums below 1200 feet (350 m) RVR are required to have a low visibility taxi plan.
　
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