Consistency with data trace
I have read with interest all possible explanations suggested here fot the incorrect AOA readings.
My humble contribution would be to ask to all future posters to make any theory somehow match with the data trace.
It has a very specific behaviour: 10 or 12 degrees offset, higher on the left at power - up, fairly stable on both sides, then during taxi hardly any real movement at any side, but several (6 or 8) short instances of left AOA vane reading ramping up a few degrees at a time, not vertically (cliff) but at a slope, increasing the offset to about 25 deg, then at rotation the right one increases (normal) the left one decreases (abnormal) and then both set at 22 degrees offset and seem to measure quite faithfully to each other (apart from the offset) for the rest of the flight.
(numbers are very rough guess, trends are right though)
To me the only two explanations that so far match (loosely) are:
- a slipping shaft that slips with the bumps but sticks with aero forces (but two sensors in a row, I don't think so)
- a intermittent electrical connection outside of the probe somewhere in a encoder-like signal which is disturbed by the bumps of taxi and creates an offset. Perhaps at the control module or power to the probe.
I don't think any of them is very probable, though. There must be a better explanation. Although bit corruption or software bug doesn't fit any better to me.
edit: another plausible but quite crazy scenario would be a voltage reference for analog signals drifting up and the electronic box going for the higher value of the sin cos signals instead of simply ruling them unsuitable because the plausibility check failed.