During our recent aircraft overhaul, the directional gyro and attitude
indicator got re-plumbed.  They were originally in a real tangled octopus.
But, now both come off the same hose using T connectors.  Beautifully neat
and simple.

However, now we have a weird new problem.  The attitude indicator gets all
the vacuum.  Virtually nothing reaches the gyro.  This overspeeds the
attitude indicator.

The attitude indicator is at the end of the vacuum hose, and the DG is in
the middle.  So, as a test I completely disconnected the DG and left the
connector OPEN.  But, even when I COMPLETELY DISCONNECT the DG and leave the
hose open at that T connector, the attitude indicator at the end still gets
almost a full 7 inches of vacuum.  (Far too much.)

THIS AIN'T LOGICAL!  There must be some trick to vacuum plumbing that the AI
does not discern, and that I cannot deduce.

Any knowledge to offer?

 

Dave Winters

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