(2)
DG heading input
(3)
Heading servo null
(4)
Servo loop control transformer (CT) rotor continuity
(5)
Magnetic field sensor excitation current
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34-21-02 Page 6 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Oct 20/84
G. Failure of the monitored functions results in loss of the super flag output voltage (28 volts dc nominal)from the coupler. In addition, a latching indicator on the front of the coupler trips when heading servo loop failure occurs.
6. Radio Digital Distance Magnetic Indicators (RDDMI)
A. Magnetic heading information from the compass coupler is displayed on a rotating compass dial which is read against a fixed index at the top of the indicator.
7. Horizontal Situation Indicator (HSI)
A. The HSI’s are on the captain’s and first officer’s instrument panels. Heading information from data transmitters in the compass coupler is fed to resolvers in the indicators. The resolvers develop a signal relative in phase and magnitude to the heading signals. The resolver signal is amplified and drives a synchro-motor which positions a rotating compass card to indicate the heading against a fixed index at the top of the indicator. The synchro-motor also drives a rate generator which provides a rate signal to the resolver to null the heading signal as the rotating compass card is positioned to the correct heading.
B. A flag logic circuit in the indicators senses indicator resolver outputs and heading valid signals from the compass couplers. As long as all signals are present, the heading flag is held out of view. If any of the signals are lost, the heading flag will appear at the fixed heading marker at the top of the indicator.
8. AFCS Panel Controller
A. The controller contains three groups of synchros: heading, left (captain’s) course and right (first officer’s) course.
B. The heading section comprises four synchro-resolvers whose rotor shafts are connected together with a control knob which permits the rotors to be preset to any desired heading, resulting in the HSI heading marker indicating the selected heading in the radio mode.
C. The two course sections are similar comprising two synchro-resolvers in each with the rotor shafts connected to a control knob which permits a desired course to be preset on the HSI course arrow.
Oct 20/84 34-21-02 Page 7
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
9. Compass Transformers
A. Compass transformers No. 1 and 2, which provide synchro excitation for the captain's and first officer's instruments, are located on electronics shelf E1-2.
10. Operation (Fig. 4 and 5)
A. General
(1)
Heading and heading valid signals from the directional gyro systems are provided to the compass couplers. These directional gyro heading signals are used to damp the magnetic heading signals from the magnetic flux valves.
(2)
The gyro stabilized magnetic heading outputs from the compass couplers are applied to the radio digital distance magnetic indicators and to compass cards in the horizontal situation indicators (Fig. 4 and 5).
(3)
DG 1 provides stabilization signals to compass coupler 1 which in turn supplies stabilized magnetic heading to the captain's HSI and the F/O's RDDMI. DG 2 supplies stabilization signals to compass coupler 2 which in turn normally supplies stabilized magnetic heading to the first officer's HSI and captain's RDDMI.
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