I know several people who have done the pitch
gain resistor change with their Stec. It is common and routinely done to
correct the oscillations many airplane models experience, especially experimentals.
Some people solder in short leads to put a variable resistor on the outside which
allows testing various resistances to get the best result before making the
resistor change permanent. Stec should have documentation available to guide
you or bring the unit to an avionics shop to do it. You should be able to find
several shops that have done this before.
There should also be builders here who
have gone through this and can share their experiences.
-Neal
Glasair IISRG N15F (will put the autopilot
in “soon”)
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf
Of Wayne Bailey
Sent: Sunday, October 12, 2008
8:49 PM
To: lml@lancaironline.net
Subject: [LML] Blue Mountain
Avionics Autopilot
Small tail 360 with Stec50 autopilot.
AP works OK to maintaining heading - but pitch
enters oscillations eventually becoming so severe requires disconnection
of AP after about 30 - 40 seconds. Incredibly there is no 'gain'
adjustment in the pitch axis of the STEC 50. I have read about
replacing resistor on board to modify gain - but a little
uncomfortable with this option. No slop in the linkage.
Have not dug into the servos yet - but hoping there is a
way to mechanically reduce the 'gain' by extending the servo attachment point
radially outward on bellcrank - or ??
Alternatively thinking about installing BMA EFIS Gen
4 system with new servo actuators. Anyone have any experience with BMA
gen 4 EFIS on a close coupled LNC2? I do know there is gain on both
axis.
Thanks again for the help.
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