APR 2017 Chapter 95 Instrument System Page 95.13
95-26 Magnetic Compass
A. Description
An internally illuminated, wet-type compass is attached to the center bow between
the windshields above the instrument panel.
B. Schematic
Refer to Figure 98-1 for electrical schematic.
C. Removal
1. Remove hardware securing B339-2 mount to windshield bow.
2. Remove hardware securing B148-5 compass assembly to mount.
3. Remove heat shrink as required and disconnect light bar wires from airframe
harness. Remove compass.
D. Installation
1. Install heat shrinks over wires and connect B148-5 compass assembly’s light bar
wires to airframe harness. Verify security. Activate heat shrinks.
2. Install hardware securing compass to B339-2 mount. Verify security.
3. Install hardware securing mount to windshield bow. Verify security.
4. Using the airport compass rose, align the helicopter skids on the rose lines, and
record the indicated compass headings at 30° increments. Adjust compass
compensator magnets as required until the maximum error at any heading is 5°
or less with all avionics operating, all exterior lights on, and dimmer full bright.
Record the final readings on the aircraft compass card. Re-check 4 cardinal
headings with lights off and all avionics off except COM radio 1 and transponder.
Verify maximum error remains 5° or less.
E. Scheduled Maintenance and Inspections
Refer to § 5-45 100-Hour/Annual Inspection.
F. Special Maintenance and Inspections
1. Perform compass deviation check per Part D step 4.
2. If compass cannot be adjusted to limits specified, remove compass per Part C,
and install airworthy compass per Part D.
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