Piper SEMINOLE PA-44-180, Maintenance Manual

Page: 531 / 881

(4). Press tape will into threads.
(5). Screw fitting into port being careful not to exceed torque requirements noted on decal on then cover of
the gyro.
3. Vacuum Gauge:
A. Vacuum gauge seldom requires service and usually is replaced when malfunctions occur.
— Note —
Vacuum gauge failure in a properly operating vacuum system does not impair safety
of flight.
B. If the vacuum gauge malfunctions in a manner to cause an incorrect reading in normal cruise
conditions, the gave must be checked by comparing the reading with a gauge of known accuracy. If
the gauge is indicating correct values and the system vacuum level is not in accordance with the
specified vacuum, then and only then should the regulator to be reset.
C. Visual examination of the gauge performance should cover the following steps:
(1). With engine stopped and no vacuum applied to the gauge, its pointer should rest against the internal
stop in the 9 o’clock position. Any other displacement from this position suggests need for
replacement.
(2). A slight overshoot, during engine startup, not to exceed half an inch (1/2") of mercury, is normal and is
not cause to replace gauge.
(3). With engine operating at normal cruise RPM, the gauge should read from 4.9 inches to 5.1 inches of
mercury (vacuum).
(4). At 1200 RPM, the vacuum gauge reading should be more than four inches of mercury.
4. Gyro Filter:
A. Gyro filter must be serviced on a scheduled basis, not to exceed 100 hours, or sooner as condition
indicates.
B. The system installation employs a large central filter and differential vacuum gauge that continuously
monitors the filter condition while indicating a vacuum readings.
— Note —
The vacuum system employs a central filter in combination with a differential vacuum
gauge which will indicate a decline in panel gauge reading when the filter becomes
clogged and vacuum declines below the recommended value. The filter should be
replaced when gauge reading declines below the recommended value; do not adjust
regulator.
5. Vacuum Regulator:
A. The vacuum regulating valve seldom needs replacement. Symptoms that suggest replacement are:
(1). Chatter as indicated by rapid fluctuation of the vacuum gauge needle or an audible sound.
(2). Non-repeatability of the vacuum gauge reading when the panel gauge is not suspect or has been
checked against a known test gauge (cruise RPM only).
B. Regulator malfunction tends to increase the vacuum power applied to the gyros. Thus, although
excess vacuum is applied, a loss of vacuum does not occur.
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
3 7 - 11 - 0 0
Page 37-06
Revised: May 15, 1989
2K13
PIPER AIRCRAFT