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helicopter pitch attitude. With a given power setting and
pitch attitude, the airspeed remains constant. If the airspeed
increases, the nose is too low and should be raised. If the
airspeed decreases, the nose is too high and should be
lowered. A rapid change in airspeed indicates a large change
in pitch attitude, and a slow change in airspeed indicates a
small change in pitch attitude. There is very little lag in the
indications of the airspeed indicator. If, while making attitude
changes, there is some lag between control application and
change of airspeed, it is most likely due to cyclic control lag.
Generally, a departure from the desired airspeed, due to an
inadvertent pitch attitude change, also results in a change in
altitude. For example, an increase in airspeed due to a low
pitch attitude results in a decrease in altitude. A correction in
the pitch attitude regains both airspeed and altitude.
Bank Control
The bank attitude of a helicopter is the angular relation of
its lateral axis to the natural horizon. To maintain a straight
course in visual flight, keep the lateral axis of the helicopter
level with the natural horizon. Assuming the helicopter is in
coordinated flight, any deviation from a laterally level attitude
produces a turn. [Figure 6-4]
Attitude Indicator
The attitude indicator gives a direct indication of the bank
attitude of the helicopter. For instrument flight, the miniature
aircraft and the horizon bar of the attitude indicator are
substituted for the actual helicopter and the natural horizon.
Any change in bank attitude of the helicopter is indicated
instantly by the miniature aircraft. For proper interpretation
of this instrument, imagine being in the miniature aircraft. If
the helicopter is properly trimmed and the rotor tilts, a turn
begins. The turn can be stopped by leveling the miniature
aircraft with the horizon bar. The ball in the turn-and-slip
indicator should always be kept centered through proper
pedal trim.
The angle of bank is indicated by the pointer on the banking
scale at the top of the instrument. [Figure 6-5] Small bank
angles, which may not be seen by observing the miniature
aircraft, can easily be determined by referring to the banking
scale pointer.
6-6
Figure 6-5. The banking scale at the top of the attitude indicator indicates varying degrees of bank. In this example, the helicopter is
banked approximately 15° to the right.
Figure 6-4. The flight instruments used for bank control are the attitude, heading, and turn indicators.
Pitch-and-bank attitudes can be determined simultaneously
on the attitude indicator. Even though the miniature aircraft
is not level with the horizon bar, pitch attitude can be
established by observing the relative position of the miniature
aircraft and the horizon bar.
The attitude indicator may show small misrepresentations
of bank attitude during maneuvers that involve turns. This
precession error can be detected immediately by closely
cross-checking the other bank instruments during these
maneuvers. Precession is normally noticed when rolling
out of a turn. If, upon completion of a turn, the miniature
aircraft is level and the helicopter is still turning, make a
small change of bank attitude to center the turn needle and
stop the movement of the heading indicator.
Heading Indicator
In coordinated flight, the heading indicator gives an indirect
indication of a helicopter’s bank attitude. When a helicopter is
banked, it turns. When the lateral axis of a helicopter is level,
it flies straight. Therefore, in coordinated flight when the
heading indicator shows a constant heading, the helicopter is
level laterally. A deviation from the desired heading indicates
a bank in the direction the helicopter is turning. A small angle
of bank is indicated by a slow change of heading; a large angle
of bank is indicated by a rapid change of heading. If a turn
is noticed, apply opposite cyclic until the heading indicator
6-7
Figure 6-6. Coordinated flight is indicated by centering of the ball.
indicates the desired heading, simultaneously ensuring the
ball is centered. When making the correction to the desired
heading, do not use a bank angle greater than that required
to achieve a standard rate turn. In addition, if the number
of degrees of change is small, limit the bank angle to the
number of degrees to be turned. Bank angles greater than
these require more skill and precision in attaining the desired
results. During straight-and-level flight, the heading indicator
is the primary reference for bank control.
　
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本文鏈接地址：Instrument Flying Handbook儀表飛行手冊上(120)