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I see there are quite a few posts on the LML forum regarding vacuum pumps.
In my own 10,000+ hours of flying light aircraft I’ve only seen a couple of
failures. I’ve never had a failure of a 200 series pump, only the 400
series pumps. The 400 series are used in applications with pneumatic
deicers. The 400 series failures I’ve had were in twins where I flew the
pumps until failure. One pump got over 1000 hours which is quite
remarkable.

The Baron I fly now (air taxi) requires a pump change every 600 hours to
maintain the flight in known icing certification.

I can offer several recommendations to insure long pump life.

1. Change the filters at recommended intervals.

2. Use only Airborne unrestricted fittings. Standard AN fittings will
restrict flow and reduce pump life. This applies on both inlet and outlet
sides. Pump vane life is shortened by inlet or outlet restrictions.

3. Don’t let engine cleaning solvent or any other contaminants anywhere
near the pump. Don’t use anything but tiny amounts of lube on fittings and
don’t use Teflon tape.

4. Check the cork pad gasket for signs of oil leakage. Oil leaks at the
drive seal can allow oil to get inside the pump and cause failure.

5. Check the system for leaks. Any leakage makes the system work harder and
shortens pump life. Don’t blindly adjust the pressure regulator without
checking for leaks. Regulators rarely need adjustment.

6. Keep all contaminants out of the system. When I install pumps or filters
I use a vacuum cleaner on all components prior assembly. Just screwing in
new fittings in the pump can let tiny amounts of grit fall into the pump.

7. Keep the pump cool. Install a cooling shroud or blast tube to keep the
pump cool during normal operation.

8. On vacuum (as compared with pressure) systems note the location of the
inlet filter. On a Piper Archer I once owned the main inlet filter was
located on the upper corner of the firewall inside the cabin. The
windshield had a slight water leak which dripped on the filter and resulted
in moisture inside the gyros. I had several gyro failures before I figured
this one out. Only after the overhaul shop told me they found rust inside
the gyros did it dawn on me what was happening.

If you do experience a pump failure don't freak out. Practice partial panel
occassionally. I've successfully flown practice ILS approaches to minimums
without heading or attitude gyros. A handy little trick for a substitute
heading indicator is to use an ADF (assuming you still have one). Tune the
ADF to a distant AM radio station and use the needle as a heading
REFERENCE. Using a station a hundred or more miles away will allow you to
hold a constant heading by reference to the ADF needle over short distances
such as during an ILS approach.

Good luck,


Ted Stanley
Legacy 2000 depositor
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