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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
STANDBY ATTITUDE REFERENCE SYSTEM - DESCRIPTION AND OPERATION
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General
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A. The standby attitude reference system is a standby navigational aid. It functions as an independent system which provides a visual display of airplane attitude in pitch and roll at all times during flight. The indicator also displays instrument landing system (ILS) data.
B. The system consists of the standby attitude/ILS indicator and a static inverter/ILS processor (Fig. 1).
C. The system receives ILS data from the left ILS receiver. A gyro within
the indicator provides the attitude display.Standby Attitude/ILS Indicator
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A. The indicator provides attitude and ILS displays.
B. Attitude is provided by a vertical gyro connected to a sphere-type roll and pitch attitude display. The display has 107 degrees of freedom in climb, 63 degrees of freedom in dive and 360 degrees of freedom in roll.
C. The ILS display consists of horizontal and vertical deviation bars. Rectangular divisions on each deviation bar are used as a scale, for the other deviation bar, to determine the amount of deviation from an on course approach. The deviation bars are driven by signals from the left ILS receiver.
D. A caging knob is used to mechanically accelerate the erection of the vertical gyro.
E. ILS display modes are controlled by a three-position rotary mode select switch on the indicators front face.
F. Three warning flags are provided for failure indication. The glide path (G/P) and lateral failure (LAT) flags come into view for invalid ILS data and failures in the static inverter/ILS processor. The GYRO warning flag appears when the gyro rotor speed is either too low or high and for failures in the static inverter/ILS processor.
Static Inverter/ILS Processor
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A. The static inverter/ILS processor performs two functions. The static inverter circuitry provides power to the gyro and controls the GYRO warning flag. The ILS processor circuitry controls the G/P and LAT failure flags and uses ILS data to drive the glide path and lateral deviation bars.
Standby Attitude Reference System Interface
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A. The standby attitude reference system interfaces with the ILS navigation system (Ref 34-31-00).
B. The ILS navigation system provides glide path and lateral deviation signals to drive the horizontal and vertical deviation bars in the standby attitude/ILS indicator. The ILS navigation system also provides glide path and lateral valid signals to control the G/P and LAT warning flags in the standby attitude/ILS indicator.
Functional Description (Fig. 2)
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A. Power Distribution
(1) The static inverter/ILS processor receives 28-volt dc power from the STBY INSTR ILS IND and STBY INSTR ATTD IND circuit breakers on the overhead circuit breaker panel P7.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
PILOT'S CENTER
INSTRUMENT PANEL
SEE A
GLIDE PATH
ROLL DEVIATION BAR GYRO
POINTER FAILURE
FLAG
ROLL
SCALE
PITCH
SCALE
GLIDE
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