Sender: "Marvin Kaye" <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Mon, 18 Oct 2004 09:32:27 -0400
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From: "Gary Casey" <glcasey@adelphia.net>
Subject: Re:  S-TEC 50 Problem - LNC2
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<<The pressure transducer, however, appears flaky.  Probing the back of the
connector indicates an open circuit in the signal path in the transducer.
Although this could be the contact inside the connector too, since I was
only able to probe the harness side.  The transducer seemed to work on the
bench (signal moved properly with pressure change, but my setup could not
rule out intermittencies). I removed the connector and attached the leads
directly to the male pins on the transducer with higher quality female
contacts.  Result seemed better than before, but a full down command still
occurred, and the system hunted excessively (50 foot excursions up and
down).
Thanks,
Ed de Chazal>>

If you can part with the pressure transducer for a few days I'd be happy to
check it out for you - we are the manufacturer.  You won't learn anything by
probing with an ohm-meter as the sensors are active devices.  Monitoring the
output while flying is a good way to check them out, though the extra wire
connected could possibly cause an EMI issue that will confuse things.
Interestingly, my Cessna with an S-TEC 30 installed, is having the same
sorts of problems although I have an experimental sensor installed that
shouldn't suffer from this sort of thing.  I haven't had a chance to check
it out.  Also, the symptoms you describe, while not impossible, are an
unusual failure mode for a sensor.  A flaky static system can create 50 feet
of uncertainty as well - is the sensor connected to the static system or is
it measuring pressure inside the cabin?

Gary Casey