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the airplane when flying on instruments. The pilot can tell if
the turn is coordinated by checking the ball in the turn-andslip
indicator or the turn coordinator. [Figure 2-15]
As the aircraft banks to enter a turn, a portion of the wing’s
vertical lift becomes the horizontal component; therefore,
without an increase in back pressure, the aircraft loses altitude
during the turn. The loss of vertical lift can be offset by
increasing the pitch in one-half bar width increments. Trim
may be used to relieve the control pressures; however, if used,
it has to be removed once the turn is complete.
In a slipping turn, the aircraft is not turning at the rate
appropriate to the bank being used, and the aircraft falls to
the inside of the turn. The aircraft is banked too much for the
rate of turn, so the horizontal lift component is greater than
the centrifugal force. A skidding turn results from excess of
centrifugal force over the horizontal lift component, pulling
the aircraft toward the outside of the turn. The rate of turn
is too great for the angle of bank, so the horizontal lift
component is less than the centrifugal force.
The ball instrument indicates the quality of the turn, and
should be centered when the wings are banked. If the ball
is off of center on the side toward the turn, the aircraft is
slipping and rudder pressure should be added on that side to
increase the rate of turn or the bank angle should be reduced.
If the ball is off of center on the side away from the turn,
the aircraft is skidding and rudder pressure toward the turn
should be relaxed or the bank angle should be increased.
If the aircraft is properly rigged, the ball should be in the
center when the wings are level; use rudder and/or aileron
trim if available.
The increase in induced drag (caused by the increase in angle
of attack necessary to maintain altitude) results in a minor
loss of airspeed if the power setting is not changed.
Load Factor
Any force applied to an aircraft to deflect its flight from a
straight line produces a stress on its structure; the amount of
this force is termed load factor. A load factor is the ratio of
2-12
2 MIN TURN
DC ELEC
L R
TURN COORDINATOR
2 MIN.
ELEC.
L R
NO PITCH
INFORMATION
2 MIN TURN
DC ELEC
L R
TURN COORDINATOR
2 MIN.
ELEC.
L R
NO PITCH
INFORMATION
2 MIN TURN
DC ELEC
L R
TURN COORDINATOR
2 MIN.
ELEC.
L R
NO PITCH
INFORMATION
Skidding Turn
Skidding Turn
Slipping Turn
Slipping Turn
Coordinated Turn
rudder into turn
Coordinated Turn
Note the slight differences in rudder placement.
Figure 2-15. Adverse Yaw.
the aerodynamic force on the aircraft to the gross weight of
the aircraft (e.g., lift/weight). For example, a load factor of 3
means the total load on an aircraft’s structure is three times
its gross weight. When designing an aircraft, it is necessary
to determine the highest load factors that can be expected in
normal operation under various operational situations. These
“highest” load factors are called “limit load factors.”
Aircraft are placed in various categories, i.e., normal, utility,
and acrobatic, depending upon the load factors they are
designed to take. For reasons of safety, the aircraft must be
designed to withstand certain maximum load factors without
any structural damage.
The specified load may be expected in terms of aerodynamic
forces, as in turns. In level flight in undisturbed air, the
wings are supporting not only the weight of the aircraft, but
centrifugal force as well. As the bank steepens, the horizontal
lift component increases, centrifugal force increases, and the
load factor increases. If the load factor becomes so great that
an increase in angle of attack cannot provide enough lift to
support the load, the wing stalls. Since the stalling speed
increases directly with the square root of the load factor, the
pilot should be aware of the flight conditions during which the
load factor can become critical. Steep turns at slow airspeed,
structural ice accumulation, and vertical gusts in turbulent
air can increase the load factor to a critical level.
Icing
One of the greatest hazards to flight is aircraft icing. The
instrument pilot must be aware of the conditions conducive to
aircraft icing. These conditions include the types of icing, the
effects of icing on aircraft control and performance, effects
of icing on aircraft systems, and the use and limitations of
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Instrument Flying Handbook仪表飞行手册上(36)
