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referring to the turn-and-slip indicator. Then as the
sweep second hand of the clock passes a cardinal point
(12, 3, 6, or 9), check the heading on the heading indicator.
While holding the indicated rate of turn constant,
note the heading changes at 10-second intervals. If the
helicopter turns more or less than 30° in that interval, a
smaller or larger deflection of the needle is necessary
to produce a standard rate turn. When you have calibrated
the turn-and-slip indicator during turns in each
direction, note the corrected deflections, if any, and
apply them during all timed turns.
You use the same cross-check and control technique in
making timed turns that you use to make turns to a predetermined
heading, except that you substitute the
clock for the heading indicator. The needle of the turnand-
slip indicator is primary for bank control, the
altimeter is primary for pitch control, and the airspeed
indicator is primary for power control. Begin the roll-in
when the clock’s second hand passes a cardinal point,
hold the turn at the calibrated standard-rate indication,
or half-standard-rate for small changes in heading, and
begin the roll-out when the computed number of seconds
has elapsed. If the roll-in and roll-out rates are the
same, the time taken during entry and recovery need
not be considered in the time computation.
If you practice timed turns with a full instrument panel,
check the heading indicator for the accuracy of your
turns. If you execute the turns without the heading indicator,
use the magnetic compass at the completion of
the turn to check turn accuracy, taking compass deviation
errors into consideration.
CHANGE OF AIRSPEED IN TURNS
Changing airspeed in turns is an effective maneuver for
increasing your proficiency in all three basic instrument
skills. Since the maneuver involves simultaneous
changes in all components of control, proper execution
requires a rapid cross-check and interpretation, as well
as smooth control. Proficiency in the maneuver also
contributes to your confidence in the instruments during
attitude and power changes involved in more complex
maneuvers.
Pitch and power control techniques are the same as
those used during airspeed changes in straight-andlevel
flight. As discussed previously, the angle of bank
necessary for a given rate of turn is proportional to the
true airspeed. Since the turns are executed at standard
rate, the angle of bank must be varied in direct proportion
to the airspeed change in order to maintain a
constant rate of turn. During a reduction of airspeed,
you must decrease the angle of bank and increase the
pitch attitude to maintain altitude and a standard rate
turn.
The altimeter and the needle on the turn indicator
should remain constant throughout the turn. The
altimeter is primary for pitch control, and the turn needle
is primary for bank control. The torque meter is
primary for power control while the airspeed is changing.
As the airspeed approaches the new indication, the
airspeed indicator becomes primary for power control.
Two methods of changing airspeed in turns may be
used. In the first method, airspeed is changed after the
turn is established. In the second method, the airspeed
change is initiated simultaneously with the turn entry.
The first method is easier, but regardless of the method
12-17
used, the rate of cross-check must be increased as you
reduce power. As the helicopter decelerates, check the
altimeter and VSI for needed pitch changes, and the
bank instruments for needed bank changes. If the needle
of the turn-and-slip indicator shows a deviation from
the desired deflection, change the bank. Adjust pitch
attitude to maintain altitude. When the airspeed
approaches that desired, the airspeed indicator becomes
primary for power control. Adjust the torque meter to
maintain the desired airspeed. Use pedal trim to ensure
the maneuver is coordinated.
Until your control technique is very smooth, frequently
cross-check the attitude indicator to keep from overcontrolling
and to provide approximate bank angles
appropriate for the changing airspeeds.
30° BANK TURN
A turn using 30° of bank is seldom necessary, or advisable,
in IMC, but it is an excellent maneuver to increase
your ability to react quickly and smoothly to rapid
changes of attitude. Even though the entry and recovery
technique are the same as for any other turn, you
will probably find it more difficult to control pitch
because of the decrease in vertical lift as the bank
increases. Also, because of the decrease in vertical lift,
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ROTORCRAFT FLYING HANDBOOK2(28)
