Sunday, March 15, 2009

Takeoff Roll - Crosswind Takeoff

The technique used during the initial takeoff roll in a
crosswind is generally the same as used in a normal
takeoff, except that aileron control must be held INTO
the crosswind. This raises the aileron on the upwind
wing to impose a downward force on the wing to counteract
the lifting force of the crosswind and prevents
the wing from rising.

As the airplane is taxied into takeoff position, it is essential
that the windsock and other wind direction indicators
be checked so that the presence of a crosswind may be
recognized and anticipated. If a crosswind is indicated,
FULL aileron should be held into the wind as the takeoff
roll is started. This control position should be maintained
while the airplane is accelerating and until the ailerons
start becoming sufficiently effective for maneuvering the
airplane about its longitudinal axis.

With the aileron held into the wind, the takeoff path
must be held straight with the rudder. Crosswind takeoff roll and initial climb.

Normally, this will require applying downwind rudder
pressure, since on the ground the airplane will tend to
weathervane into the wind. When takeoff power is
applied, torque or P-factor that yaws the airplane to the
left may be sufficient to counteract the weathervaning
tendency caused by a crosswind from the right. On the
other hand, it may also aggravate the tendency to

swerve left when the wind is from the left. In any case,
whatever rudder pressure is required to keep the airplane rolling straight down the runway should be

As the forward speed of the airplane increases and the
crosswind becomes more of a relative headwind, the
mechanical holding of full aileron into the wind should
be reduced. It is when increasing pressure is being felt
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. Crosswind effect.

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
side slipping into the wind enough to counteract drift.

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