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on the aileron control that the ailerons are becoming
more effective. As the aileron’s effectiveness increases
and the crosswind component of the relative wind
becomes less effective, it will be necessary to gradually
reduce the aileron pressure. The crosswind component
effect does not completely vanish, so some aileron pressure
will have to be maintained throughout the takeoff
roll to keep the crosswind from raising the upwind wing.
If the upwind wing rises, thus exposing more surface to
the crosswind, a “skipping” action may result. [Figure
5-4]
This is usually indicated by a series of very small
bounces, caused by the airplane attempting to fly
and then settling back onto the runway. During these
bounces, the crosswind also tends to move the airplane
sideways, and these bounces will develop into
side-skipping. This side-skipping imposes severe
side stresses on the landing gear and could result in
structural failure.
It is important, during a crosswind takeoff roll, to hold
sufficient aileron into the wind not only to keep the
upwind wing from rising but to hold that wing down so
that the airplane will, immediately after lift-off, be
sideslipping into the wind enough to counteract drift.
LIFT-OFF
As the nosewheel is being raised off the runway, the
holding of aileron control into the wind may result in
the downwind wing rising and the downwind main
wheel lifting off the runway first, with the remainder
of the takeoff roll being made on that one main wheel.
This is acceptable and is preferable to side-skipping.
If a significant crosswind exists, the main wheels
should be held on the ground slightly longer than in a
normal takeoff so that a smooth but very definite liftoff
can be made. This procedure will allow the airplane
to leave the ground under more positive control
so that it will definitely remain airborne while the
proper amount of wind correction is being established.
More importantly, this procedure will avoid imposing
excessive side-loads on the landing gear and prevent
possible damage that would result from the airplane
settling back to the runway while drifting.
As both main wheels leave the runway and ground
friction no longer resists drifting, the airplane will be
slowly carried sideways with the wind unless adequate
drift correction is maintained by the pilot. Therefore, it
is important to establish and maintain the proper
amount of crosswind correction prior to lift-off by
applying aileron pressure toward the wind to keep the
upwind wing from rising and applying rudder pressure
as needed to prevent weathervaning.
INITIAL CLIMB
If proper crosswind correction is being applied, as soon
as the airplane is airborne, it will be sideslipping into the
wind sufficiently to counteract the drifting effect of the
wind. [Figure 5-5] This sideslipping should be continued
until the airplane has a positive rate of climb. At that time,
the airplane should be turned into the wind to establish
just enough wind correction angle to counteract the wind
and then the wings rolled level. Firm and aggressive use
of the rudders will be required to keep the airplane headed
straight down the runway. The climb with a wind correction
angle should be continued to follow a ground track
aligned with the runway direction. However, because the
force of a crosswind may vary markedly within a few
hundred feet of the ground, frequent checks of actual
ground track should be made, and the wind correction
adjusted as necessary. The remainder of the climb technique
is the same used for normal takeoffs and climbs.
Common errors in the performance of crosswind takeoffs
are:
• Failure to adequately clear the area prior to taxiing
onto the active runway.
• Using less than full aileron pressure into the
wind initially on the takeoff roll.
• Mechanical use of aileron control rather than
sensing the need for varying aileron control
input through feel for the airplane.
No correction
WIND
WIND
Proper correction
Figure 5-4. Crosswind effect.
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5-7
• Premature lift-off resulting in side-skipping.
• Excessive aileron input in the latter stage of the
takeoff roll resulting in a steep bank into the wind
at lift-off.
• Inadequate drift correction after lift-off.
GROUND EFFECT ON TAKEOFF
Ground effect is a condition of improved performance
encountered when the airplane is operating
very close to the ground. Ground effect can be
detected and measured up to an altitude equal to one
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(57)
