445 Cardinal Lane
Hartland, WI 53029 USA
Phone (262) 367-2292
Fax (262) 367-7158
www.rapco-rfs.com

SB Number: # RAS007          Date: JUNE 16, 1994

With the increasing age of the world aircraft fleet out there, we are seeing an alarming number of vacuum pump cores and warranty pumps come back with small pieces of rubber in them.

It is very important when replacing a dry air pump to clean out the vacuum or pressure lines (using an air gun or even pressure washer, then letting it dry). In addition to cleaning the carbon out it is also very important to carefully inspect any of the air lines you can get at. This is usually done by removing the lines and visually looking for small loose pieces of foreign material in the hose or falling out of the hose. It sometimes helps to place a piece of white paper under the hose, bend the hose and look for small pieces to fall onto it. There is only .001 to .003 clearance between the internal rotor and the cavity wall of a dry air pump. This means a piece that small will fail that pump! Usually, this occurs when you first start up the engine. It can get very costly replacing pumps as opposed to the labor time of cleaning and inspecting the lines.

We recommend that at 5000 hours in operation or every 5 years the vacuum lines should be replaced. Especially those lines exposed to the engine compartment. These lines are not only exposed to the heat of the engine and possible turbocharger heat, but they have more exposure to the ozone that causes the break down of the hoses internally. Also, note when installing new lines to carefully slide the hose onto the air fittings without gouging a piece out of the rubber line. This will keep a piece of rubber from falling into the pump and failing the pump upon start up.

In addition to not using anything on the threads of the fitting, we ask that you keep the above points in mind when changing a dry air pump. This, along with proper and frequent air filter changes, will extend the life of your vacuum pump considerably!

Sincerely,

Michael R. Lotzer
Sales Manager