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runway centerline. The greater the amount of crab at touchdown, the larger the
lateral deviation from the point of touchdown. For this reason, touchdown in a
crab only condition is not recommended when landing on a dry runway in strong
crosswinds.
On very slippery runways, landing the airplane using crab only reduces drift
toward the downwind side at touchdown, permits rapid operation of spoilers and
autobrakes because all main gears touchdown simultaneously, and may reduce
pilot workload since the airplane does not have to be de-crabbed before
touchdown. However, proper rudder and upwind aileron must be applied after
touchdown to ensure directional control is maintained.
Sideslip (Wing Low)
The sideslip crosswind technique aligns the airplane with the extended runway
centerline so that main gear touchdown occurs on the runway centerline.
The initial phase of the approach to landing is flown using the crab method to
correct for drift. Prior to the flare the airplane centerline is aligned on or parallel
to the runway centerline. Downwind rudder is used to align the longitudinal axis
to the desired track as aileron is used to lower the wing into the wind to prevent
drift. A steady sideslip is established with opposite rudder and low wing into the
wind to hold the desired course.
Touchdown is accomplished with the upwind wheels touching just before the
downwind wheels. Overcontrolling the roll axis must be avoided because
overbanking could cause the engine nacelle or outboard wing flap to contact the
runway. (See Ground Clearance Angles - Normal Landing charts, this chapter.)
Properly coordinated, this maneuver results in nearly fixed rudder and aileron
control positions during the final phase of the approach, touchdown, and
beginning of the landing roll. However, since turbulence is often associated with
crosswinds, it is often difficult to maintain the cross control coordination through
the final phase of the approach to touchdown.
October 31, 2006
777/787 Flight Crew Training Manual
Landing
Copyright © The Boeing Company. See title page for details.
FCT 777/787 Preliminary (TM) 6.45
If the crew elects to fly the sideslip to touchdown, it may be necessary to add a
crab during strong crosswinds. (See the landing crosswind guidelines table, this
chapter). Main gear touchdown is made with the upwind wing low and crab angle
applied. As the upwind gear touches first, a slight increase in downwind rudder is
applied to align the airplane with the runway centerline. At touchdown, increased
application of upwind aileron should be applied to maintain wings level.
Overweight Landing
Accomplish the Overweight Landing non-normal checklist.
Overweight landings may be safely accomplished by using normal landing
procedures and techniques. There are no adverse handling characteristics
associated with overweight landings. Landing distance is normally less than
takeoff distance for flaps 20, 25, or 30 landings at all gross weights. However, wet
or slippery runway field length requirements should be verified from the landing
distance charts in the PI Chapter of the QRH. Brake energy limits will not be
exceeded under any normal or non-normal landing conditions.
If stopping distance is a concern, reduce the landing weight as much as possible.
At the captain’s discretion, consider fuel jettison or reduce weight by holding at
low altitude with a high drag configuration (gear down) to achieve maximum fuel
burn-off.
Observe flap placard speeds during flap extension and on final approach. In the
holding and approach patterns, maneuvers should be flown at the normal
maneuver speeds. During flap extension, airspeed can be reduced by as much as
20 knots below normal maneuver speeds before extending to the next flap
position. These lower speeds result in larger margins to the flap placards, while
still providing normal bank angle maneuvering capability, but do not allow for a
15° overshoot margin in all cases.
Use the longest available runway, and consider wind and slope effects. Where
possible avoid landing in tailwinds, on runways with negative slope, or on
runways with less than normal braking conditions. Do not carry excess airspeed
on final. This is especially important when landing during an engine inoperative
or other non-normal condition. At weights above the maximum landing weight,
the final approach maximum wind correction may be limited by the flap placards
and load relief system.
Fly a normal profile. Ensure that a higher than normal rate of descent does not
develop. Do not hold the airplane off waiting for a smooth landing. Fly the
airplane onto the runway at the normal touchdown point. If a long landing is likely
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787机组训练手册Flight Crew Training Manual 787(106)
