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and that all controls, including flaps and trim tabs,
are set in accordance with the before takeoff checklist.
In addition, the pilot must make certain that the
approach and takeoff paths are clear of other aircraft.
At uncontrolled airports, pilots should announce their
intentions on the common traffic advisory frequency
(CTAF) assigned to that airport. When operating from
an airport with an operating control tower, pilots must
contact the tower operator and receive a takeoff clearance
before taxiing onto the active runway.
It is not recommended to take off immediately behind
another aircraft, particularly large, heavily loaded
transport airplanes, because of the wake turbulence
that is generated.
While taxiing onto the runway, the pilot can select
ground reference points that are aligned with the
runway direction as aids to maintaining directional
control during the takeoff. These may be runway
centerline markings, runway lighting, distant trees,
towers, buildings, or mountain peaks.
NORMAL TAKEOFF
Anormal takeoff is one in which the airplane is headed
into the wind, or the wind is very light. Also, the takeoff
surface is firm and of sufficient length to permit the
airplane to gradually accelerate to normal lift-off and
climb-out speed, and there are no obstructions along
the takeoff path.
There are two reasons for making a takeoff as nearly
into the wind as possible. First, the airplane’s speed
while on the ground is much less than if the takeoff
were made downwind, thus reducing wear and stress
on the landing gear. Second, a shorter ground roll and
therefore much less runway length is required to
develop the minimum lift necessary for takeoff and
climb. Since the airplane depends on airspeed in order
to fly, a headwind provides some of that airspeed, even
with the airplane motionless, from the wind flowing
over the wings.
TAKEOFF ROLL
After taxiing onto the runway, the airplane should be
carefully aligned with the intended takeoff direction,
and the nosewheel positioned straight, or centered.
After releasing the brakes, the throttle should be
advanced smoothly and continuously to takeoff power.
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. This will be most apparent
in high horsepower engines. As the airplane starts to
roll forward, the pilot should assure both feet are on
the rudder pedals so that the toes or balls of the feet are
on the rudder portions, not on the brake portions.
Engine instruments should be monitored during the
takeoff roll for any malfunctions.
In nosewheel-type airplanes, pressures on the elevator
control are not necessary beyond those needed to
steady it. Applying unnecessary pressure will only
aggravate the takeoff and prevent the pilot from recognizing
when elevator control pressure is actually
needed to establish the takeoff attitude.
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
engine torque and P-factor at the initial speeds tend to
pull the nose to the left. The pilot must use whatever
rudder pressure and aileron 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 this will cause slower acceleration of the airplane’s
speed, lengthen the takeoff distance, and
possibly result in severe swerving.
While the speed of the takeoff roll increases, more
and more pressure will be felt on the flight controls,
particularly the elevators and rudder. If the tail surfaces
are affected by the propeller slipstream, they
become effective first. As the speed continues to
increase, all of the flight controls will gradually
become effective enough to maneuver the airplane
about its three axes. It is at this point, in the taxi to
flight transition, that the airplane is being flown more
than taxied. As this occurs, progressively smaller
rudder deflections are needed to maintain direction.
The feel of resistance to the movement of the controls
and the airplane’s reaction to such movements
are the only real indicators of the degree of control
attained. This feel of resistance is not a measure of
the airplane’s speed, but rather of its controllability.
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(53)
