11. Flight Instrument Accessory Unit
A. A flight instrument accessory unit is located in electronic equipment rack E-1. The unit contains relays and printed circuit for signal conditioning and interface between the navigation systems and the flight instruments. In addition, the unit contains a solid-state circuit for automatic dimming of the approach progress display lights in the flight director system.
B. The flight instrument accessory unit circuits associated with the VOR/ILS navigation system consist of the diodes across the solenoids of the nav transfer relays and two instrument transformers. The transformers provide 26 volts ac to the navigation units and to the RMI's.
C. On GJ B-2504 and B-2505, the flight instrument accessory unit also contains the VOR/ILS self-test inhibit relay. The relay is energized to prevent actuation of a VOR/ILS self-test when channel A of the autopilot system is engaged in any mode other than manual.
12. Operation
A. To operate the VOR/ILS navigation system, energize load control center P6 and P18 and close the circuit breakers shown in Fig. 3. Also, position the VHF NAV and COMPASS transfer switches on the overhead panel to NORMAL, the NAV transfer switches on the captain's and first officer's instrument panels to RADIO, and select VOR for the RMI bearing pointers. Tune the systems to the local VOR/ILS station and check that the station audio output is available through the interphone system.
B. Taking one system as an example: rotation of the remote course knob selects the desired VOR/LOC course and positions the HSI course arrow. At the time the course arrow is positioned, the selected course is also displayed on the course counter. The manual resolver and course select synchro are also positioned in accordance with the selected course. A signal from the resolver is fed to the manual VOR portion of the navigation unit, when after comparison in the phase detector, it is fed back as the VOR deviation signal to deflect the course deviation bar.
C. Position of the course deviation bar with respect to the miniature airplane, shows real airplane position with respect to the selected course. The course deviation scale dots are referenced points for showing airplane angular displacement from the selected course. TO-FROM indication is shown by a pointer which appears from behind the course deviation scale near the center of the HSI. As the airplane passes over the selected VOR ground station, the to/from annunciation reverses 180 degrees.
D. VOR ground station bearing is displayed by the RMI bearing pointers. The narrow pointer displays VOR-1 bearing while VOR-2 bearing is displayed by the wide pointer. Tuning to an ILS frequency parks the associated pointer at the 3 o'clock position.
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Oct 20/87 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-31-0 Page 7
E. Selecting an ILS frequency enables the ADI and HSI localizer and glide slope displays for making an instrument landing approach.
F. Localizer deviation is displayed by the ADI runway symbol and the HSI course deviation bar which move laterally across a scale to show airplane deviation from the localizer beam.
G. Glide slope information is displayed by the glide slope pointers in the ADI and HSI. The pointers remain horizontal and move vertically across the scale to show airplane deviation about the glide path.
H. When the system is tuned to a VOR frequency, the ADI and HSI glide slope flags and pointers and the ADI runway flag and symbol are biased out-of-view.
I. The VOR/LOC super flag signals control the respective ADI RUNWAY and HSI NAV warning flags.
J. The glide slope super flag signals control the respective ADI and HSI GS warning flags.
K. A system self-test feature is controlled by test switches on the VHF NAV control panel.
L. For VOR test, a VOR station is tuned in and a course of zero degrees is selected. When the VOR self-test is actuated, test displays on the associated instruments are as follows:
(1)
HSI course deviation bar centered
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