(c)
Place compass transfer switch in BOTH ON NO. 1 position.
(d)
Using captain's RMI SYNC knob, rotate compass card through 360 degrees in 15-degree increments. Check that first officer's RMI and HSI compass cards follow smoothly and repeat each setting within ± 1 degree. Check that captain's HSI follows smoothly and repeats each setting within ± 2 degrees.
(e)
Place compass transfer switch in BOTH ON NO. 2 position.
(f)
Using first officer's RMI SYNC knob, rotate compass card through 360 degrees in 15-degree increments. Check that captain's RMI and HSI follow smoothly and repeat each setting within ± 1 degree. Check that first officer's HSI follows smoothly and repeats each setting within ± 2 degrees.
(4)
Compass Warning Tests
(a)
Check system malfunction warning test using following table. Open circuit breakers listed one at a time and close at completion of each section. Check that flags appearing upon opening of a circuit breaker disappear when that circuit breaker is closed.
(b)
Place compass transfer switch in normal position.
541
34-21-0 Page 502 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 01/75
STEP COMPASS TRANSFER SWITCH POSITION OPEN CIRCUIT BREAKER FLAG APPEARS ON
1 NORMAL COMPASS-1 CAPT RMI & F/O HSI
2 NORMAL COMPASS-2 F/O RMI & CAPT HSI
3 NORMAL INSTR XFMR-1 F/O HSI
4 NORMAL INSTR XFMR-2 CAPT HSI
5 BOTH ON NO. 1 COMPASS-1 CAPT RMI & HSI; F/O RMI & HSI
6 BOTH ON NO. 1 CAPT RMI (ALT) F/O RMI & CAPT HSI
7 BOTH ON NO. 1 INSTR XFMR-1 F/O RMI & HSI; CAPT HSI
8 BOTH ON NO. 1 INSTR XFMR-2 CAPT HSI
9 BOTH ON NO. 2 COMPASS-2 F/O RMI & HSI; CAPT RMI & HSI
10 BOTH ON NO. 2 F/O RMI (ALT) CAPT RMI & F/O HSI
11 BOTH ON NO. 2 INSTR XFMR-1 F/O HSI
12 BOTH ON NO. 2 INSTR XFMR-2 CAPT RMI & HSI; F/O HSI
13 BOTH ON NO. 1 INVERTER CONTROL F/O RMI & CAPT HSI
D. If no longer required, remove electrical power from the airplane.
Nov 01/75 34-21-0 Page 503
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
COMPASS SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
GJ B-2509 and B-2510 NZ ALL EXCEPT ZK-NAC thru ZK-NAS and ZK-NQC WA ALL EXCEPT N4502W thru N4530W, N4569N, N4571M, and N235WA
1. General
A. The compass system provides gyro stabilized magnetic heading information to the airplane flight instruments at the captain's and first officer's stations, and to interfacing systems. Two separate systems are installed in the airplane.
B. One complete system consists of a flux valve, directional gyro, a compass coupler, a compass controller, and radio digital distance magnetic indicators (RDDMI) (Fig. 1). Magnetic heading is also displayed on compass cards in the captain's and first officer's horizontal situation indicators (HSI).
C. The airplane magnetic heading displayed on the RDDMI's and HSI's is also applied to other airplane systems. Fast synchronization of the flight instrument compass cards (700 degrees per minute) is accomplished when power is first applied, the platform heading input is switched to a new source, or the operating mode is changed.
D. The compass system provides two modes of operation, the SLAVED mode and the DG mode.
(1)
The SLAVED mode of operation is normally used at latitudes up to approximately 65 degrees where magnetic compass information is generally reliable. In this mode the magnetic heading output from the magnetic field sensor is synchronized with the heading output from the directional gyro (DG). The SLAVED mode, in effect, provides directional gyro stabilized heading information with magnetic sense. The slaved mode offers long-term heading stability within its latitude range.
(2)
The DG mode of operation is normally used at latitudes higher than 65 degrees because of large and unpredictable magnetic errors encountered at the higher latitudes. In this mode, system input information is limited to heading from the directional gyro system. Heading accuracy is dependent upon errors inherent in the directional gyro system and is irrespective of magnetic field variations. The DG mode offers only short-term heading stability, therefore heading information in this mode must be frequently updated to maintain its integrity.
Oct 20/84 34-21-02 Page 1
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