Saturday, March 21, 2009

Lift-Off - Ground Effect On Takeoff

Approaching best angle-of-climb speed (VX), the airplane
should be smoothly and firmly lifted off, or rotated, by
applying back-elevator pressure to an attitude that will
result in the best angle-of-climb airspeed (VX). Since the
airplane will accelerate more rapidly after lift-off, additional back-elevator pressure becomes necessary to hold a
constant airspeed. After becoming airborne, a wings level
climb should be maintained at VX until obstacles have
been cleared or, if no obstacles are involved, until an altitude of at least 50 feet above the takeoff surface is attained.
Thereafter, the pitch attitude may be lowered slightly, and
the climb continued at best rate-of-climb speed (VY) until
reaching a safe maneuvering altitude. Remember that an
attempt to pull the airplane off the ground prematurely, or
to climb too steeply, may cause the airplane to settle back
to the runway or into the obstacles. Even if the airplane
remains airborne, the initial climb will remain flat and
climb performance/obstacle clearance ability seriously
degraded until best angle-of-climb airspeed (VX) is
achieved. Effect of premature lift-off

The objective is to rotate to the appropriate pitch attitude at (or near) best angle-of-climb airspeed. It should
be remembered, however, that some airplanes will
have a natural tendency to lift off well before reaching
VX. In these airplanes, it may be necessary to allow the
airplane to lift off in ground effect and then reduce
pitch attitude to level until the airplane accelerates to
best angle-of-climb airspeed with the wheels just clear
of the runway surface. This method is preferable to
forcing the airplane to remain on the ground with forward-elevator pressure until best angle-of-climb speed
is attained. Holding the airplane on the ground unnecessarily puts excessive pressure on the nosewheel, may
result in "wheelbarrowing," and will hinder both
acceleration and overall airplane performance.

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