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From: "John Huft" <aflyer@lazy8.net>
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Subject: [LML] Re: Blue Mountain Avionics Autopilot
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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.
Wayne
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<p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>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.<o:p></o:p></span></p>
<p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Pitch oscillations are the main symptoms of too much =
static lag.<o:p></o:p></span></p>
<p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>John Huft<o:p></o:p></span></p>
<p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>RV spy<o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
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<p class=3DMsoNormal><b><span =
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span>=
</b><span
style=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Lancair =
Mailing
List [mailto:lml@lancaironline.net] <b>On Behalf Of </b>Wayne Bailey<br>
<b>Sent:</b> Sunday, October 12, 2008 6:49 PM<br>
<b>To:</b> lml@lancaironline.net<br>
<b>Subject:</b> [LML] Blue Mountain Avionics =
Autopilot<o:p></o:p></span></p>
</div>
<p class=3DMsoNormal><o:p> </o:p></p>
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<div>
<p class=3DMsoNormal>Small tail 360 with Stec50 autopilot. =
<o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal>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.<o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal>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 ??<o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal>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.<o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal>Thanks again for the help.<o:p></o:p></p>
</div>
<div>
<p class=3DMsoNormal><br>
<br>
Wayne<o:p></o:p></p>
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