Old 2nd Jan 2019, 14:03
  #62 (permalink)  
Join Date: Jun 2009
Location: florida
Age: 76
Posts: 1,084
and Happy New Year!

@ 'bird, et al..... re: digitizing the analogs. Even way back in the early 90's most of our analog signals were digitized by single purpose chips. A very few really "special" systems would have the A2D conversion circuits as part of a much more complex chip/ckt board versus separate components. In a very few cases dealing with analog sensors that had no A2D data used by more than one subsystem ( think guidance seekers, we had to "capture" the signals before they got to the "user" box in order to properly troubleshoot.

The previous gripes seem to all concern airspeed disagreement and such, and the AoA faults only showed up when maintenance codes were examined. As I understand it, some of the systems use AoA to "condition" the airspeed indications and such. Someplace between those values used for displays/STS and the AoA source should bear the brunt of investigation besides a "simple" mounting error. Considering that the speed gripes were there before the AoA vane change, I tend to rule out the sensor itself and its internal electronics.

Is it the sensor? Is it a BB rolling around on the ckt board? Is it a dip switch setting that lets the A2D processing account for left versus right sensor? And so forth.

So I like looking at the SMYD for the problem. Hell. just yank the thing out and replace! Not possible now, but we may see a similar sequence in another plane and we could keep this one in mind if a gripe shows up two times in a row.

Gums sends..

Last edited by gums; 2nd Jan 2019 at 14:16. Reason: revised wording, typos
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