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the airplane in the desired attitude using the primary
flight controls. The proper attitude should be established
with reference to the horizon and then verified
by reference to performance indications on the
flight instruments. The pilot should then apply trim
in the above sequence to relieve whatever hand and
foot pressure had been required. The pilot must
avoid using the trim to establish or correct airplane
attitude. The airplane attitude must be established
and held first, then control pressures trimmed out
so that the airplane will maintain the desired attitude
in “hands off” flight. Attempting to “fly the
airplane with the trim tabs” is a common fault in
basic flying technique even among experienced
pilots.
A properly trimmed airplane is an indication of good
piloting skills. Any control pressures the pilot feels
should be a result of deliberate pilot control input during
a planned change in airplane attitude, not a result
of pressures being applied by the airplane because the
pilot is allowing it to assume control.
LEVEL TURNS
Aturn is made by banking the wings in the direction of
the desired turn. Aspecific angle of bank is selected by
the pilot, control pressures applied to achieve the
desired bank angle, and appropriate control pressures
exerted to maintain the desired bank angle once it is
established. [Figure 3-5]
All four primary controls are used in close coordination
when making turns. Their functions are as follows.
• The ailerons bank the wings and so determine the
rate of turn at any given airspeed.
• The elevator moves the nose of the airplane up or
down in relation to the pilot, and perpendicular to
the wings. Doing that, it both sets the pitch attitude
in the turn and “pulls” the nose of the airplane
around the turn.
• The throttle provides thrust which may be used for
airspeed to tighten the turn.
• The rudder offsets any yaw effects developed by
the other controls. The rudder does not turn the airplane.
For purposes of this discussion, turns are divided into
three classes: shallow turns, medium turns, and steep
turns.
• Shallow turns are those in which the bank (less
than approximately 20°) is so shallow that the
inherent lateral stability of the airplane is acting to
level the wings unless some aileron is applied to
maintain the bank.
• Medium turns are those resulting from a degree of
bank (approximately 20° to 45°) at which the airplane
remains at a constant bank.
Figure 3-5. Level turn to the left.
Ch 03.qxd 7/13/04 11:08 AM Page 3-7
3-8
Steep turns are those resulting from a degree of
bank (45° or more) at which the “overbanking
tendency” of an airplane overcomes stability, and
the bank increases unless aileron is applied to
prevent it.
Changing the direction of the wing’s lift toward one
side or the other causes the airplane to be pulled in that
direction. [Figure 3-6] Applying coordinated aileron
and rudder to bank the airplane in the direction of the
desired turn does this.
When an airplane is flying straight and level, the total lift
is acting perpendicular to the wings and to the Earth. As
the airplane is banked into a turn, the lift then becomes
the resultant of two components. One, the vertical lift
component, continues to act perpendicular to the Earth
and opposes gravity. Second, the horizontal lift component
(centripetal) acts parallel to the Earth’s surface and
opposes inertia (apparent centrifugal force). These two
lift components act at right angles to each other, causing
the resultant total lifting force to act perpendicular to the
banked wing of the airplane. It is the horizontal lift component
that actually turns the airplane—not the rudder.
When applying aileron to bank the airplane, the lowered
aileron (on the rising wing) produces a greater drag than
the raised aileron (on the lowering wing). [Figure 3-7]
This increased aileron yaws the airplane toward the rising
wing, or opposite to the direction of turn. To counteract
this adverse yawing moment, rudder pressure must be
applied simultaneously with aileron in the desired
direction of turn. This action is required to produce a
coordinated turn.
After the bank has been established in a medium
banked turn, all pressure applied to the aileron may be
relaxed. The airplane will remain at the selected bank
with no further tendency to yaw since there is no
longer a deflection of the ailerons. As a result, pressure
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(27)
