Jay Honeck wrote:
I'd check to make sure that there is suction to the instrument, not just
visual inspection of the hoses, before I removed it from the plane.

How would you recommend going about doing that?
I've not seen what's up there for myself -- how are the hoses attached
to the instruments? How do you check for vacuum? Detach the hose and
stick your finger over it?

You could removed the line from your panel mounted vacuum gauge and attach
it directly to the suction hose going into your DG (remove the hose
completely from the DG, don't use a "T" at first). This way you're
isolating the vacuum comming from the regulator. You may need an adapter,
because I believe they're generally use a smaller hose to the gauge than
the hose to the instruments. A decent avionics shop, or even a well
equipped maintenance shop should be able to apply a vacuum to the
instrument using a bench mounted vacuum pump to check it out. I agree
that most vacuum instruments die slowly, not suddenly.

The hoses are generally hooked to the instrument with either a barbed
adapter, or an adapter with a single "ridge" flaired into it. This type
is the type where you'd use a hose clamp. It's generally not needed with
the barbed adapter, although it's often used anyway.

The "schematic" for your vacuum system is likely the following:

+----- DG ------+
| |
filter regulator ----- vacuum pump
| |
+----- AI ------+
|
+----- vacuum gauge

direction of air flow ------------

Note that both the filter, and the firewall mounted regulator have two
ports on them. The vacuum gauge is often driven by an auxilary port
on either the AI (as pictured) or the DG. I think you can also have it
fed by a "T" off the normal lines to one of the instruments.

-- Jay


__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino/ ! ! !

Checkout http://www.oc-adolfos.com/
for the best Italian food in Ocean City, MD and...
Checkout http://www.brolow.com/ for authentic Blues music on Delmarva