CSP-HMI-3MD Helicopters, Inc.
MAINTENANCE MANUAL
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[ Chapter 95 TOC ]
95-20-00
Page 201
Revision 7
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Neither this document nor any part hereof may be reproduced or transferred to
other documents or used or disclosed to others for manufacturing or any other
purpose except as specifically authorized in writing by MD Helicopters, Inc.
Copyright © 1999−2016 by MD Helicopters, Inc.
MAGNETIC COMPASS
MAINTENANCE PRACTICES
1. Magnetic Compass
(Ref. Figure 201 for 369D helicopters,
Figure 202 for 369E/FF - 500/600N helicop
ters) The magnetic compass is attached to the
center canopy frame. The compass face is tilted
down at an angle so that it is level during
normal flight. It is internally illuminated from
the night lighting system (Ref. Sec. 96-40-00).
2. Magnetic Compass Troubleshooting
(Ref. Table 201)
Table 201. Troubleshooting Magnetic Compass
Symptom Probable Trouble Corrective Action
Excessive error External magnetic interference Locate and eliminate magnetic
interference.
Defective bearings Replace magnetic compass.
Improper compensation Compensate compass as required,
perform Magnetic Compass Ground
Swinging.
Excessive oscillation Insufficient liquid in bowl Replace compass.
Rotating element not level Leaking float chamber Replace compass.
Magnets detached from rotating
element
Replace compass.
Sluggish operation Dirty jewels or pivots Replace compass.
Weak card magnets Replace compass.
Liquid leakage or bubbles visible
under normal flight conditions
Defective gasket or float chamber Replace compass.
A. Magnetic Compass Maintenance
Practices
(Ref. Instruments Replacement, Instrument
Inspection, and Instrument Repair, Sec.
95-00-00)
3. Magnetic Compass Ground Swinging
NOTE: Helicopter must be placed in simulated
flight condition while swinging the compass.
(1). Position helicopter on compass rose.
(2). Ensure that all controls and equipment
are placed in normal flight position and
that the area is magnetically clean.
(3). Use helicopter ground handling wheels
or equivalent to support helicopter
when rotating to different headings.
(4). Start helicopter engine according to
standard PFM instructions.
(5). Turn on power to all equipment, except
landing light. Allow approximately
three minutes for equipment functions
to stabilize.
NOTE: All personnel required to be near or on
the helicopter during the compass swing
must be free of magnetic materials.
(6). Set E-W and N-S adjustments screws
on standby compass to zero by aligning
the dot on the screw with the dot on the
frame.
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