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Question
Sir:
On the last several flights I noticed the instrument pressure
gage was reading lower than normal (about 4.5). When I first
bought the aircraft, a Beech V35, the gage always seemed
to be about 5.0. Everything seems to be working OK except
that I just replaced my air pump for the 2 nd time with only
325 hours.
The CV1J4 “Clearview” filter I had installed
on the last pump change, reached the “Replace Filter” point
at about 320 hours. Am I being sold bad air pumps or is it
my aircraft?
Ron D.
Jacksonville, Fl.
Answer
Mr. D.
Before we point a finger at the FBO or air pump manufacturer,
let’s look at a few things you can check on your aircraft.
Since you didn’t mention the air pump model number,
I assume you have a model 212 (warranted for 1000 hours)
or a model 242 (normally warranted for 400 hours). Either
way, your air pumps are operating well below the curve.
Being
your aircraft is an older model, the first thing I would check
are the hose clamps, both in the engine compartment and behind
the panel.
| When first installed, ‘Spring Clamps” are
quick and easy, preventing pressure or vacuum leakage
at the connection |
|
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Due to normal aging of the hose, especially under
adverse conditions in the engine compartment, the hose
will deform and become loose on the air fitting. Since
there is no way to “retighten” the clamp,
pressure/vacuum from the system is lost. |
| Bottom Line !
If you have “Spring Clamps” at the hose
connections, replace them with “Screw Type” clamps. |
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A pressure gage reading of 5.0 Hg. is only equivalent
to 2.5 psi., a small pressure that can be affected by many
small and seemingly insignificant leaks.
While you’re inspecting behind the panel, also make
sure someone hasn’t replaced the pneumatic hose with
surgical tubing, another problem we covered in Q & A
#1.
For additional information on the proper procedures in
checking your aircraft and increasing air pump performance,
go to the DATA SHEETS section of our web site, click on “Pressure
Systems” and then select “Operation & Testing.
R. Heysek
Aerotech Components, Inc
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