Directional Gyro Troubleshooting; Gyro Fitting Installation Procedure - Piper PA-44-180 SEMINOLE Maintenance Manual

TROUBLESHOOTING.
Unless an obvious malfunction of the instrument (such as constantly spinning dial) requires repair or
replacement of the directional gyro, service is restricted to the instrument installation and power (air/ electric)
requirements. Typical installation examples of gyro instrument malfunctions are due to installation system
problems such as: restricted airflow due to air line kinks or leaks, contaminated air filters, deteriorating electrical
grounds, sagging instrument panel shock mounts, system regulators, faulty vacuum/pressure gauges, etc.
Excessive precession is a common complaint and usually results from installation problems such as described
above, or can be the result of pilot operating error. While directional gyro precession can only be exactly
measured under closely controlled conditions in an approved gyro overhaul facility, any complaint of abnormal
precession should be initially confirmed on the compass rose.
Normal precession of the directional gyro is ±3° in 10 minutes or ±4° in 10 minutes if
four cardinal headings are used and the total precession does not exceed 12°.
When confirming precession complaints on the compass rose, aircraft position must be established by nose
wheel alignment with the compass rose lines. Under no conditions should the magnetic compass be used for
comparison. Otherwise, the deviation of the magnetic compass heading can be read mistakenly as precession.
Finally, only after abnormal precession has been confirmed and the system installation proven good should the
instrument be "pulled" for replacement or repair.
REMOVAL AND REPLACEMENT.
Refer to Chapter 39, Removal and Replacement of Face Mounted Instruments.

GYRO FITTING INSTALLATION PROCEDURE.

The following procedure applies to these aircraft having Edo-Aire air driven gyro installation. The use of
tenon tape on fitting threads is recommended.
PERMIT NO OIL, GREASE, PIPE COMPOUND OR ANY FOREIGN
MATERIAL TO ENTER PARTS PRIOR TO INSTALLATION OF FITTINGS.
MAKE CERTAIN ALL AIR LINES ARE CLEAN AND FREE OF FOREIGN
PARTICLES AND/OR RESIDUE BEFORE CONNECTING LINES TO GYRO.
Use of thread lube on fittings or in parts will create a "warranty void" condition.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— Note —
Air pressure must be 5.5 ± .5 psig.
— Note —
— CAUTION —
— Note —
2J3
3 4 - 2 2 - 0 5
Page 34-09
Revised: May 15, 1989