1.
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COMPASS SYSTEM - TROUBLE SHOOTING
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 location of troubles in the compass system can best be determined by a systematic functional test. Use of unit electrical schematics, block diagrams, and electronic wiring diagrams of the compass system will aid in trouble shooting analysis. Trouble shooting the compass system is best accomplished by substituting components where possible.
B. The flux valve (remote compass transmitter) is extremely sensitive to magnetic fields and will malfunction if it is near magnetic materials which distort the earth's magnetic field.
CAUTION: DO NOT CHECK THE FLUX VALVE WITH AN OHMMETER. DIRECT CURRENT IN THE WINDINGS MAY MAGNETIZE THE CORES.
C. Before proceeding with the trouble shooting procedures, recheck that the compass transfer switch is in normal position and all compass system circuit breakers are closed. Check that cable connectors are properly mated and securely connected. Check that 400 cycle ac synchro excitation is present to all units. When substituting known good units in place of suspected malfunctioning units, leave replacement units in the circuit until trouble is cleared and then replace original good units into the operating system.
D. The following trouble shooting procedures are for compass system No. 1. If trouble is encountered in compass system No. 2, use the same procedure substituting, in the procedure, with an equivalent compass system No. 2 component.
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COMPASS SYSTEM - ADJUSTMENT/TEST
EFFECTIVITY
WA ALL EXCEPT N4502W thru N4530W, N4569N, N4571M, and N235WA
GJ B-2509 and B-2510
1. Compass Systems Test
A. General
(1)
The following tests should be carried out prior to compass compensation procedure, which is detailed in Compass System - Maintenance Practices.
(2)
The tests are designed to check out the serviceability of the system and not its accuracy.
B. Prepare System for Test
(1)
Connect external power and close ground power switch on panel P5 or make use of APU.
(2)
Check that the following circuit breakers are closed:
COMPASS No. 1 COMPASS No. 2 INSTR XFMR-1 F/O COMPASS XFMR ALTN CAPT COMPASS XFMR ALTN VOR/ILS No. 2 INSTR TRANSFER INSTR XFMR-2 VOR/ILS No. 1 P5 radio and 28V DC T-R buses all AFCS Circuit Breakers
(3)
Set the DG - SLAVED switch on the Capt's and F/O's compass controllers (located on the pilot's overhead panel) in the SLAVED position.
(4)
Ensure that the HEADING flags on the Capt's and F/O's RDDMI and HSI are out of view and both compass systems are synchronized to airplane heading, and the MAG annunciator on both HSIs is in view.
(5)
Tune the VHF NAV receivers to a VOR frequency (108.00 MHz).
C. Test Compass Systems
(1) Monitoring
(a) In the following tests, open the indicated circuit breaker. The indicated warning flags shall come into view within 2 seconds. After checking the flags, close the circuit breaker. Verify that all compass warning flags are out of view before proceeding to the next step.
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(2)
Fast Synchronization
(a)
Synchronize both compass systems to airplane heading. The synch annunciator on both compass controllers shall indicate a null.
(b)
Set the DG-SLAVED switch on the Captain's compass controller to DG. By means of SET HDG knob on the Captain's compass controller, rotate the compass card on the Captain's HSI to a heading of approximately 60° from airplane heading in a decreasing direction. The synch annunciator on the Capt's compass controller shall indicate a null. The Capt's HSI compass card shall match the F/O's RDDMI within 2 degrees.
(c)
Set the DG-SLAVED switch to SLAVED. Within one minute the compass card on the Captain's HSI shall return to airplane heading and the synch annunciator shall indicate null.
(d)
By means of SET HDG knob, rotate the compass card on the Captain's HSI to a heading of approximately 60° from airplane heading in a decreasing direction. The synch annunciator on the Capt's compass controller shall indicate a left deflection.
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