Piper Aircraft Corporation Malibu Mirage PA-46-350P, Airplane Maintenance Manual

Page: 950 / 1956

PAGE 4
Feb 28/07
5D8
34-20-00
PIPER AIRCRAFT, INC.
PA-46-350P, MALIBU MIRAGE
MAINTENANCE MANUAL
3. Horizontal Situation Indicator (HSI) or Electronic Horizontal Situation Indicator (EHSI)
The HSI or EHSI, which combines pictorial VOR/ILS Localizer indications with an electrical heading
indicator, is the pilot's primary heading indicator. The gyro is not in the instrument case, but is located on
the accessory shelf in the tail section of the airplane. The gyro is slaved to the earth's magnetic field
through a flux detector (i.e. - flux gate compass) installed in the leading edge of the vertical stabilizer.
Should the slaving mechanism become inoperative, the heading gyro can be deslaved through a switch
on slave controlled unit mounted on the extreme upper left section of the pilot's instrument panel. Once
deslaved, the heading gyro becomes free running, making it susceptible to gyroscopic precession. The
compass control unit includes a spring loaded to OFF switch marked as CW (clockwise) or CCW
(counterclockwise), used to electrically drive the remote gyro to correct the heading indication for any
precession. The system is protected through the 3 amp COMPASS circuit breaker located on the
copilot's C/B panel
A. Troubleshooting
See Chart 3.
B. Removal and Installation
See 39-10-00, Face Mounted Instruments - Removal and Installation.
Trouble Cause Remedy
Heading card "frozen" 3 amp COMPASS circuit Reset breaker, if open.
regardless if gyro is slaved breaker open.
or deslaved.
Faulty remote gyro unit. Replace gyro unit.
Break in wiring between remote Check and repair broken
gyro and instrument. wire(s).
Faulty Indicator (Instrument). Replace Indicator.
Heading card "frozen" or Bad flux detector. Replace flux detector.
erratic when slaved, but
works satisfactorily when
Faulty remote gyro unit. Replace gyro unit.
deslaved.
Compass card erratic whether Faulty remote gyro unit. Replace gyro unit.
slaved or deslaved.
Faulty Indicator (Instrument). Replace Indicator.
When deslaved, compass card Faulty compass control unit. Replace compass control
will not respond to CW or CCW control unit.
commands.
Faulty remote gyro unit. Replace gyro unit.
CHART 3
TROUBLESHOOTING ELECTRIC HEADING INDICATOR