Table 2-11. Standby Attitude Indicator Control / Functions T3
Moveable sphere with line between colors to indicate the earths horizon.
Rotates with aircraft to provide measurement of angular displacement by the roll pointer.
Indicates vertical in any roll attitude.
Indicates earth's horizon relative to aircraft pitch attitude.
Rotated to adjust the miniature aircraft.
Measures pitch displacement of miniature aircraft.
Represents aircraft nose and wings. Indicates roll and pitch attitude relative to the
horizon. Adjustable through pitch knob for varying pitch attitudes.
c. Description F3 OSA . The standby attitude
reference system, Figure 2-40, is comprised of the
attitude indicator located on the extreme left center of
the pilot's instrument panel and a 28 Vdc emergency
power supply. They provide a visual indication of the
aircraft flight attitude. The attitude reference system is
designed to provide a standby attitude indicator that is
powered by a source independent of the aircraft
electrical generating system. The system will provide
reliable attitude information for at least 30 minutes
after a total failure of the aircraft electrical system.
The power supply contains sealed lead-acid batteries
with a rating of 5.0 ampere hours. During normal
operation, the aircraft 28 Vdc system supplies power
to the indicator and power supply batteries. In the
event aircraft electrical power fails, the standby power
supply will take over the duties of powering the attitude
The attitude indicator is a 28 Vdc powered
electrically driven gyro and contains an inverter circuit
board for converting the 28 Vdc input to 22 Vac 400
Hz for indicator operation. The power warning flag is
rotated out of sight by a flag motor that allows the flag
to appear if one or more phases of power are
interrupted. The flag motor also allows the flag to
appear if the PULL TO CAGE knob is in the caged
position. The rotor speed and the mechanical erection
system enables the indicator to provide a minimum of
9 minutes of useful attitude information after complete
electrical power interruption.
A three-position switch and a three legend
annunciator unit located below the indicator provide
system control, test and visual indication of the system
status. The three position switch, placarded ON / OFF
/ TEST (normally OFF), provides control and test
capabilities of the battery powered system. While in
the normal OFF position, the annunciator, placarded
AUX ARM, will be illuminated indicating the system
batteries are being maintained in a charged condition
and the system is in a standby (non-active) mode. In
the TEST position, a check of the battery pack
illuminates the AUX TEST annunciator.
Placed in the ON position, it activates the
Standby Horizon Indicator system and illuminates the
AUX ON annunciator, provided the system circuit
breaker is set.
Table 2-12 describes the functions of the
Indicators, and Functions.
(1) Bank Angle Scale. Used in conjunction
with bank angle pointer to indicate aircraft bank angle.
(2) Bank Angle Index. Rotates with aircraft
to provide measurement of angular displacement by
roll pointer during maneuvers.
(3) Bank Angle Pointer. The moveable bank
angle pointer indicates aircraft bank angle by moving
around a fixed bank angle scale.
(4) Pitch Angle Scale. Aircraft pitch angle
may be read under the symbolic miniature aircraft on a
vertical pitch angle scale located on the attitude drum.
(5) Horizon Line. The horizon line displays
aircraft pitch and roll attitude with respect to the earth's
(6) Caging and Pitch Trim Adjustment Knob.
This knob, placarded PULL TO CAGE, is used to
vertically adjust the symbolic miniature aircraft for
changes in the aircraft's level flight pitch attitude and to
cage the instrument.