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necessary to maintain a safe margin of control in case
there is a tendency of the airplane to nose over.
On most tailwheel-type airplanes, directional control
while taxiing is facilitated by the use of a steerable
tailwheel, which operates along with the rudder. The
tailwheel steering mechanism remains engaged when
the tailwheel is operated through an arc of about 16 to
18° each side of neutral and then automatically
becomes full swiveling when turned to a greater angle.
On some models the tailwheel may also be locked in
place. The airplane may be pivoted within its own
length, if desired, yet is fully steerable for slight turns
while taxiing forward. While taxiing, the steerable
tailwheel should be used for making normal turns and
the pilot’s feet kept off the brake pedals to avoid
unnecessary wear on the brakes.
Since a tailwheel-type airplane rests on the tailwheel
as well as the main landing wheels, it assumes a
nose-high attitude when on the ground. In most cases
this places the engine cowling high enough to restrict
the pilot’s vision of the area directly ahead of the
airplane. Consequently, objects directly ahead of the
airplane are difficult, if not impossible, to see. To
observe and avoid colliding with any objects or
hazardous surface conditions, the pilot should
alternately turn the nose from one side to the
other—that is zigzag, or make a series of short S-turns
while taxiing forward. This should be done slowly,
smoothly, positively, and cautiously.
NORMAL TAKEOFF ROLL
After taxiing onto the runway, the airplane should be
carefully aligned with the intended takeoff direction,
and the tailwheel positioned straight, or centered. In
airplanes equipped with a locking device, the tailwheel
should be locked in the centered position. After
releasing the brakes, the throttle should be smoothly
and continuously advanced to takeoff power. As the
airplane starts to roll forward, the pilot should slide
both feet down on the rudder pedals so that the toes or
balls of the feet are on the rudder portions, not on the
brake portions.
An abrupt application of power may cause the airplane
to yaw sharply to the left because of the torque effects
of the engine and propeller. Also, precession will be
particularly noticeable during takeoff in a tailwheeltype
airplane if the tail is rapidly raised from a three
point to a level flight attitude. The abrupt change of
attitude tilts the horizontal axis of the propeller, and
the resulting precession produces a forward force on
the right side (90° ahead in the direction of rotation),
yawing the airplane’s nose to the left. The amount of
force created by this precession is directly related to
the rate the propeller axis is tilted when the tail is
raised. With this in mind, the throttle should always be
advanced smoothly and continuously to prevent any
sudden swerving.
Smooth, gradual advancement of the throttle is very
important in tailwheel-type airplanes, since
peculiarities in their takeoff characteristics are
accentuated in proportion to how rapidly the takeoff
power is applied.
As speed is gained, the elevator control will tend to
assume a neutral position if the airplane is correctly
trimmed. At the same time, directional control should
be maintained with smooth, prompt, positive rudder
corrections throughout the takeoff roll. The effects of
torque and P-factor at the initial speeds tend to pull the
nose to the left. The pilot must use what rudder
pressure is needed to correct for these effects or for
existing wind conditions to keep the nose of the
airplane headed straight down the runway. The use of
brakes for steering purposes should be avoided, since
they will cause slower acceleration of the airplane’s
speed, lengthen the takeoff distance, and possibly
result in severe swerving.
When the elevator trim is set for takeoff, on
application of maximum allowable power, the airplane
will (when sufficient speed has been attained)
normally assume the correct takeoff pitch attitude on
its own—the tail will rise slightly. This attitude can
then be maintained by applying slight back-elevator
pressure. If the elevator control is pushed forward
during the takeoff roll to prematurely raise the tail, its
effectiveness will rapidly build up as the speed
increases, making it necessary to apply back-elevator
pressure to lower the tail to the proper takeoff attitude.
This erratic change in attitude will delay the takeoff
and lead to directional control problems. Rudder
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AIRPLANE FLYING HANDBOOK 飞机飞行手册下(54)
