Q. I own a 1999 single engine aircraft and think it is in excellent condition but on the last few flights I noticed the vacuum indicator decreasing as the aircraft climbed to altitude. Is my air pump starting to fail already?
Norm B.
Fallon, NV

A. Mr. B.
Unless you fly in excess of 150 hours a year, I doubt that your problem is the air pump. Most newly manufactured air pumps will last between 600 to 800 hours. Unless your pump has worn excessively do to an overload problem, I would check your system before any thought of a flat-out pump replacement.

I noticed that you mentioned “vacuum” along with Fallon, Nevada.

This brings to mind a problem we solved in Carefree AZ, concerning a Mooney aircraft. Seems that the connecting hose between the gyro instruments and the vacuum gage was surgical tubing. With the extremely dry weather in that area (Phoenix, AZ) the tubing had deteriorated to the point that a vacuum could not be maintained in the system. Replacement of the surgical tubing with 1/4 in pneumatic hose solved the problem. Total cost $3.56.

This situation was reported in the April issue of the MAPA Log. (Mooney Pilots Association Magazine). A close-up on the failed surgical tubing is shown here. Notice the gage connection

Regardless of what model aircraft flown, a decrease in vacuum or pressure during climb is usually an indication of a deteriorated hose, loose hose clamp or even a cracked and leaking indicator gage. There are a lot of items to check before pointing a finger at the
air pump. What ever you do:

Do not adjust the regulator in an effort to fix this problem!

Regulator adjustment in this case would only shorten pump life.

Let us know what you find and
Fly “Heads Up“,

R. Heysek
Aerotech Components, Inc.

For a complete (down-loadable) outline on the operation and testing of “Vacuum” or
“Pressure” gyro instrument systems, see our section entitled “Data Sheets”.

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