FLIGHT
INSTRUMENTS
AIRPLANE
OPERATIONS
MANUAL
2-17-20
Page
6
Code
01
REVISION 39
AOM-145/1114
STANDBY ATTITUDE INDICATOR
The Standby Attitude Indicator is a conventional electrically powered
attitude gyro, whose primary purpose is to supply attitude information
in the event of a total loss of the PFD and MFD.
The Standby Attitude Indicator is powered by 28 V DC, from the
Essential DC Bus 2. In case of an electrical emergency, it will operate
solely on the airplane batteries, and for about 40 minutes. In case of
total electrical power loss to this equipment, it is capable of providing a
minimum of 9 minutes of useful attitude information due to high-rotor
speed and mechanical erection system. Internal lighting is provided by
5 V DC.
It is recommended that the indicator be caged before the airplane is
energized and after the airplane is deenergized. Its indication will be
reliable after its rotor speed is completely stabilized, which occurs
within 3 minutes after it is uncaged.
Any adjustment during the flight, although not normally required,
should be made by momentarily caging the indicator with the airplane
in level flight.
NOTE: Never cage an operating indicator while the airplane is pitching
or rolling.
During normal operation, Standby Attitude Indicator may present
induced errors during transient airplane conditions, such as
acceleration and deceleration or turns.
Horizontal acceleration experienced during takeoff, climb-out, descent
and landing might cause gyro precession inducing display errors.
Acceleration and decelerations ranging from 20 kt/min to 100 kt/min
may induce errors from 1° to 5° (pitch up) and from 1° to 2° (roll).
When the airplane is turning with less than 10° of bank angle, the
Standby Attitude Instrument may present induced errors of up to
2°/min. For bank angles greater than 10° it may present induced errors
around 1°/min.
During normal operation the errors are automatically corrected at a
nominal 2.5°/min when the airplane is stabilized in straight and leveled
flight.
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