The following steps should be of help when performing this operation.
1. Remove access panel at the rear of the cabin to gain access to the Schrader service valves.
—CAUTION—
Ascertain that all system pressure is released before attempting
the evacuation. (Refer to Special Servicing Procedures.)
2. Connect the manifold gauge set to the airplane service valves. (Refer to Figure 21-9.)
3. The high and low manifold hand valves should be in the closed position. (Refer to Figures 21-6 and
21-7.)
4. Connect the center manifold hose to the inlet of the vacuum pump.
—NOTE—
Make sure the exhaust port on the vacuum pump is open to avoid
damage to the vacuum pump.
5. Start the vacuum pump and open the low side manifold hand valve. Observe the compound, low
pressure gauge needle, it should show a slight vacuum.
6. Continue to operate the vacuum pump until 26 to 28 inches of vacuum is attained on the low pressure
gauge, then extend the operation for another 25 minutes.
7. If the system cannot maintain 26 to 28 inches of vacuum, close both manifold hand valves and observe
the compound gauge.
8. Should the compound gauge show a loss of vacuum, there is a leak in the system which must be
repaired before continuing with evacuation.
9. If no leaks are evident, reopen both manifold hand valves and continue the evacuation for another 30
minutes.
10. Close both manifold hand valves, stop vacuum pump and disconnect center manifold hose from the
vacuum pump.
11. Proceed to charge the system in accordance with Charging the System.
—NOTE—
The system should be charged as soon as it has been evacuated.
CHARGING THE SYSTEM.
When the system is completely evacuated in accordance with instructions given in Evacuating the System,
one of the following procedures should be used to charge the system.
21-50-12
Page 21-23
December 1, 1978
1F22
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
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