Piper SEMINOLE PA-44-180, Maintenance Manual

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GENERAL.
The instrumentation is designed to give a quick and actual indication of the attitude. performance and
condition of the airplane. Maintenance, other than described in this chapter shall be done by the instrument
manufacturer or an authorized repair station.
DESCRIPTION AND OPERATION.
The vacuum system employed to operate the gyro instruments is comprised of two engine driven dry vacuum
pumps, two vacuum regulator valves containing filters, a check valve and the necessary tubing on each engine. A
vacuum gauge is used to constantly monitor the system. If vacuum is lost from either vacuum pump or from any
other malfunction, the check valve automatically closes and vacuum is supplied by one pump. In this case one of
the two red malfunction buttons appears on the face of the gauge, indicating that vacuum is not available from
that side. An air filter is incorporated in the system to increase the life of the gyros. The filter is mounted behind
the instrument panel in the upper left-hand corner and should be replaced at each 100 hours of operation. The
instruments in this system are face mounted located on the instrument panel.
TROUBLESHOOTING.
A Troubleshooting Chart is provided to assist in locating and correcting possible malfunctions in the system.
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
3 7 - 0 2 - 0 0
Page 37-01
Revised: May 15, 1989
2K8
PIPER AIRCRAFT