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

Page: 1105 / 1956

PAGE 1
Feb 28/07 6D11
37-20-00
PIPER AIRCRAFT, INC.
PA-46-350P, MALIBU MIRAGE
MAINTENANCE MANUAL
INDICATING
Vacuum (Suction) Gauge ( S/N’s 4636001 thru 4636020 only. )
NOTE: S/N’s 4636021 and up incorporate Integrated Engine Instrumentation Systems. Refer to Section
77-40-00 for more information.
The vacuum (suction) gauge is mounted on the left-hand side of the instrument panel. This gauge is
calibrated in inches of mercury, and indicates the amount of vacuum created by the engine-driven
vacuum pumps. The total vacuum pressure, which is displayed on the vacuum gauge, is normally
regulated between 4.8 and 5.2 inches of mercury (in. Hg).
The vacuum gauge also incorporates two red flow buttons. When both pumps are operating satisfactorily,
neither flow button is visible. The left flow button will protrude should the clockwise (lower) rotating pump
fail. The right flow button will protrude should the counterclockwise (upper) rotating pump fail.
If the system filter becomes clogged or, as the lines become obstructed, the gauge will show a decrease
in pressure. Do not reset the regulator until the filter and lines have been checked. Should the vacuum
pressure from any one pump fall below the minimum pressure required, its red button will protrude from
the instrument face.
Service Tips
(1) The suction gauge seldom requires service and usually is replaced when malfunctions occur.
NOTE: Suction gauge failure in a properly operating vacuum system does not impair safety of
flight.
NOTE: Two different models of vacuum gauge may be installed in PA-46-350P airplanes. One
is marked with a normal operating range of 4.8 to 5.2 in. hg. and the other is marked
with a normal operating range of 4.5 to 5.2 in. hg. The vacuum system in a particular
airplane should be adjusted to operate in the pressure range indicated on the gauge
installed in that aircraft.
(2) If the suction gauge malfunctions in a manner to cause an incorrect reading in normal cruise
conditions, the gauge 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 be reset.
(3) Visual examination of the gauge performance should cover the following steps:
(a) With engine stopped and no vacuum supplied to the gauge, its pointer should rest against
the internal stop in the 9 o’clock position. Any displacement from this position suggests
need for replacement.
(b) A slight overshoot during engine start-up, not to exceed half an inch of Hg. (1/2 in. of
mercury, is normal and is not cause, to replace gauge)
(c) The gauge should read in the normal operating range as marked on the vacuum gauge
with engine operating at normal cruise rpm.
(d) At 1,200 rpm, the vacuum gauge reading should be more than four inches of mercury.