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John Huft,
Holy Smokes, Batman, you may have just solved my S-Tec 50 Alt hold problem, I hope !! See post and novel to Colyn.. I'll open the static to cockpit input, without a filter and see what happens, after the current paint job on 320J is done.. Hope is eternal... Don Skeele
-------------- Original message from "John Huft" <aflyer@lazy8.net>: --------------
One thing I do know about the S-Tec autopilot is that the pitch algorithms are extremely sensitive to any lag or delay in the static system. On certified installations the “brain box” is required to be mounted very close (3 feet or less) to the static ports, and the autopilot must have its own static ports, and not share them with any other instrument. Also not allowed are the little bottles that are supposed to catch moisture in the tubing.
Pitch oscillations are the main symptoms of too much static lag.
John Huft
RV spy
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Wayne Bailey
Sent: Sunday, October 12, 2008 6:49 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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One thing I do know about the S-Tec autopilot is that the pitch
algorithms are extremely sensitive to any lag or delay in the static system. On
certified installations the “brain box” is required to be mounted very close
(3 feet or less) to the static ports, and the autopilot must have its own
static ports, and not share them with any other instrument. Also not allowed
are the little bottles that are supposed to catch moisture in the tubing.
Pitch oscillations are the main symptoms of too much static lag.
John Huft
RV spy
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Wayne Bailey
Sent: Sunday, October 12, 2008 6:49 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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