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That's amusing Gary.
I have a 172rg installation with a 55X in
it. It took me almost a year to get it debugged.
Shortly after my installation (2000) there was a
big deal with larger cessna's having this problem, only this time Tom at
avionics west provided sufficient evidence that I think stec finally paid
attention.
However, there was another problem, and that was
that the dsub housing on the back of the control module cracked, making it
impossible to obtain sufficient insertion force to get a good
connection. It was from this experience that I gained a serious
respect for run-away auto-pilots. especially ones that have
auto-trim.
since then it's been very good...
Colyn
IVP with TruTrak
----- Original Message -----
Sent: Thursday, April 08, 2010 9:13
PM
Subject: [LML] Re: fixes for S-TEC 50 alt
hold
I don't know whether or not it's related, but in my Cardinal I had a
problem with my S-TEC altitude hold when it (the autopilot) was new. The
altitude hold function was divergently unstable - would start to oscillate and
then get worse and worse. Tried all sorts of static systems and finally
disconnected the static source entirely and used cabin pressure - seemed to
work slightly better. I was going back and forth with the factory -they
initially insisted there was "no problem" and said I should take it back to
the installer to have them fix their installation. Then I broadcast the
problem on the net and received replies from all over the world about the same
problem. I sent copies to S-TEC and they immediately said "send it in,"
so I did. It came back with no documentation so I called: "We just
checked it out and found no problem." Oh, yeah? I installed it and
it worked perfectly. All the earlier S-TEC autopilots, including the 55,
used analog circuitry, so the change gain components had to be changed.
They never did admit they had a problem, but I'll bet after that a lot
of owners sent theirs back for the same "inspection."
Gary
ES with TruTrack
one other comment on the static source:
the a/p doesn't care how accurate the static source is, only that it changes
with altitude. Therefore some people have found that (on spam
cans) putting a dedicated static port in just for the pressure transducer
works well.
...or you can just use the vents to fine tune your
altitude....
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