Figure 37-1. Vacuum System Installation
37-00-00
Page 37-7
Issued: April 1, 1997
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— CAUTION —
WHEN REPLACING ANY OF THE THREADED FITTINGS, DO NOT USE PIPE DOPE OR ANY OTHER ANTI-SEIZE TAPE OR COMPOUND. THE AIRBORNE AND SIGMA-TEK (EDO-AIRE) FITTINGS ARE CADMIUM P L ATED TO AVOID THE NEED FOR ANY OTHER ANTI-SEIZE MATERIALS. THE REASON FOR THIS CAUTION IS TO PROTECT THE PUMP FROM INGESTING ANY FOREIGN MATERIALS THAT COULD CAUSE PREMATURE SERVICE. REFER TO STEP TWO OF THIS SUBJECT PARAGRAPH FOR INSTALLATION OF FITTINGS.
2. Fitting Installations:
A. Make sure all air lines are clean and free of foreign material. Do not permit oil, grease. pipe compound, or any foreign material to enter the ports prior to installation of fittings.
B. With the proper fitting selected apply teflon tape as follows, refer to consumable materials chart for product acquisition.
— CAUTION —
DO NOT USE THREAD LUBE IN FITTINGS OR IN PORTS. THE USE OF THREAD LUBE CAN CAUSE CONTA M I N ATION WHICH SHORT E N S THE LIFE EXPECTANCY OF THE GYRO AND CAN CAUSE P R E M ATURE FAILURES. ANY EVIDENCE OF THREAD LUBE WILL CREATE A WARRANTY VOID CONDITION.
(1). Carefully lay the teflon tape on the threads of the fitting allowing one thread from the end of the fitting to be visible.
(2). Hold in place and wrap in the direction of the threads so the tape will remain tight fitting is installed. Make sure to apply sufficient tension while windings to assure that tape forms into thread grooves. One full wrap plus 0.5 inch overlap is sufficient.
(3). With the wrap completed, maintain tension on the tape and pull the tape in the direction of the
wrap. The resulting ragged edge is the key to securing the tape. If sheared or cut tape may loosen.
(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.
37-00-00 Page 37-8 Issued: April 1, 1997
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 diff e r e n t i a l 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.
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