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heading with the centerline of the runway,
notes the rate and direction of drift, and then promptly
applies drift correction by lowering the upwind wing.
[Figure 8-16] The amount the wing must be lowered
depends on the rate of drift. When the wing is lowered,
the airplane will tend to turn in that direction. It is then
necessary to simultaneously apply sufficient opposite
rudder pressure to prevent the turn and keep the airplane’s
longitudinal axis aligned with the runway. In
other words, the drift is controlled with aileron, and
the heading with rudder. The airplane will now be
sideslipping into the wind just enough that both the
resultant flightpath and the ground track are aligned
with the runway. If the crosswind diminishes, this
crosswind correction is reduced accordingly, or the
airplane will begin slipping away from the desired
approach path. [Figure 8-17]
To correct for strong crosswind, the slip into the wind
is increased by lowering the upwind wing a considerable
amount. As a consequence, this will result in a
greater tendency of the airplane to turn. Since turning
is not desired, considerable opposite rudder must be
applied to keep the airplane’s longitudinal axis aligned
with the runway. In some airplanes, there may not be
sufficient rudder travel available to compensate for the
strong turning tendency caused by the steep bank. If
the required bank is such that full opposite rudder will
not prevent a turn, the wind is too strong to safely land
the airplane on that particular runway with those wind
conditions. Since the airplane’s capability will be
exceeded, it is imperative that the landing be made on
Figure 8-16. Sideslip approach.
Figure 8-17. Crosswind approach and landing.
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8-15
a more favorable runway either at that airport or at an
alternate airport.
Flaps can and should be used during most approaches
since they tend to have a stabilizing effect on the airplane.
The degree to which flaps should be extended
will vary with the airplane’s handling characteristics,
as well as the wind velocity.
CROSSWIND ROUNDOUT (FLARE)
Generally, the roundout can be made like a normal
landing approach, but the application of a crosswind
correction is continued as necessary to prevent
drifting.
Since the airspeed decreases as the roundout progresses,
the flight controls gradually become less
effective. As a result, the crosswind correction being
held will become inadequate. When using the winglow
method, it is necessary to gradually increase the
deflection of the rudder and ailerons to maintain the
proper amount of drift correction.
Do not level the wings; keep the upwind wing down
throughout the roundout. If the wings are leveled, the
airplane will begin drifting and the touchdown will
occur while drifting. Remember, the primary objective
is to land the airplane without subjecting it to any side
loads that result from touching down while drifting.
CROSSWIND TOUCHDOWN
If the crab method of drift correction has been used
throughout the final approach and roundout, the crab
must be removed the instant before touchdown by
applying rudder to align the airplane’s longitudinal
axis with its direction of movement. This requires
timely and accurate action. Failure to accomplish this
will result in severe side loads being imposed on the
landing gear.
If the wing-low method is used, the crosswind correction
(aileron into the wind and opposite rudder)
should be maintained throughout the roundout, and
the touchdown made on the upwind main wheel.
During gusty or high wind conditions, prompt adjustments
must be made in the crosswind correction to
assure that the airplane does not drift as the airplane
touches down.
As the forward momentum decreases after initial
contact, the weight of the airplane will cause the
downwind main wheel to gradually settle onto the
runway.
In those airplanes having nosewheel steering interconnected
with the rudder, the nosewheel may not be
aligned with the runway as the wheels touch down
because opposite rudder is being held in the crosswind
correction. To prevent swerving in the direction the
nosewheel is offset, the corrective rudder pressure
must be promptly relaxed just as the nosewheel
touches down.
CROSSWIND AFTER-LANDING ROLL
Particularly during the after-landing roll, special
attention must be given to maintaining directional
control by the use of rudder or nosewheel steering,
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(89)
