H80100
Standby Artificial Horizon System Component Location 593
34-25-0 Figure 1 Sep 20/81
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
STANDBY ARTIFICIAL HORIZON SYSTEM -ADJUSTMENT/TEST
EFFECTIVITY
GJ ALL EXCEPT B-2509, B-2510 and B-2524
1. Standby Artificial Horizon System Test
A. General
(1) The standby artificial horizon indicator is a backup for the attitude reference system.
B. Test
(1)
Close STBY HORIZ circuit breaker located on load control panel P18.
(2)
After the instrument has been energized for 30 seconds pull the caging knob, the "X" warning flag which is visible on the right hand side of the instrument face when the system is not operating, should disappear.
(3)
Five minutes after power has been on check that the indication of pitch and roll is within + 1 degree of airplane's attitude as compared with aircraft primary attitude reference system or inclinometer.
(4)
Pull STBY HORIZ circuit breaker and observe that "X" flag comes into view.
5C8
Feb 20/89 34-25-0 Page 501
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
STANDBY ARTIFICIAL HORIZON SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
GJ B-2509, B-2510 and B-2524
1. General
A. The standby artificial horizon indicator is fitted to the airplane as a backup system for the attitude reference system. It functions as a completely independent system which provides its own visual indication of airplane attitude in pitch and roll at all times during flight.
B. Power for the system is provided from the STDBY HORIZ circuit breaker, situated on the P18 load control center.
2. Standby Artificial Horizon Indicator
A. The standby artificial horizon indicator contains an electrically-driven gyro and the necessary mechanism for its erection, an inverter unit, and a power failure motor which operates the flag. The gyro has 3600 freedom of movement in roll, and is limited in pitch to 900 in climb and 800 in dive (assuming a 50 slope on the instrument panel).
B. The face of the instrument is shown in Fig. 1. The power failure flag will show in the event of power failure or incorrect phase rotation.
C. The inverter is a solid state type of unit which supplies the 3 phase ac power for the gyro motor. Input to the inverter is 28 volts dc.
3. Operation
A. The gyro warning flag should disappear from view when power is applied and the gyro should reach operational speed in less than 3 minutes. The normal rate of erection is 30 per minute but a rapid erection device is fitted to bring about erection within a few seconds. The mechanism for rapid erection is actuated by pulling gently on the knob which is fitted to the front panel of the instrument. This operation should only be attempted when the airplane is in straight and level flight. When at rest the knob may be used to adjust the horizon line to zero pitch by turning the knob clockwise or counterclockwise. The gyro takes approximately 13 minutes to come to rest after power has been switched off.
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