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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 and the natural horizon. To maintain a
straight course in visual flight, you must 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 12-13]
ATTITUDE INDICATOR
The attitude indicator gives a direct indication of the
bank attitude of the helicopter. For instrument flight,
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Figure 12-13. The flight instruments used for bank control are the attitude, heading, and turn indicators.
12-10
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 interpretations of this instrument, you
should 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 12-
14] Small bank angles, which may not be seen by
observing the miniature aircraft, can easily be determined
by referring to the banking scale pointer.
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 immediately
detected by closely cross-checking the other bank
instruments during these maneuvers. Precession normally
is noticed when rolling out of a turn. If, on the
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 the helicopter’s bank attitude.
When a helicopter is banked, it turns. When the lateral
axis of the 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 indicates the desired
heading, simultaneously checking that the ball is centered.
When making the correction to the desired heading,
you should 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 straightand-
level flight, the heading indicator is the primary
reference for bank control.
TURN INDICATOR
During coordinated flight, the needle of the turn-andslip
indicator gives an indirect indication of the bank
attitude of the helicopter. When the needle is displaced
from the vertical position, the helicopter is
turning in the direction of the displacement. Thus, if
the needle is displaced to the left, the helicopter is
turning left. Bringing the needle back to the vertical
position with the cyclic produces straight flight. A
close observation of the needle is necessary to accurately
interpret small deviations from the desired
position.
Cross-check the ball of the turn-and-slip indicator to
determine that the helicopter is in coordinated flight. If
the rotor is laterally level and torque is properly compensated
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ROTORCRAFT FLYING HANDBOOK2(23)
