Originally Posted by
jimjim1
From preliminary report.
"PRELIMINARY
KNKT.18.10.35.04"
Copy here for now -
www.flightradar24.com/blog/wp-content/uploads/2018/10/2018-035-PK-LQP-Preliminary-Report.pdf
- At least one AoA sensor was changed immediately before penultimate flight. Presumably there was a percieved AoA sensor issue.
"replaced angle of attack sensor"
- Captain side AoA sensor showed 22 degree error for entirity of penultimate flight.
- Captain side AoA sensor showed 22 degree error for entirity of crash flight.
Perhaps the AoA sensor was not faulty and the issue lay elsewhere and was not correctly repaired?
I like** the idea of an encoding error. (**like the idea as an explanation for the observed symptoms - I don't like it that there was a crash - added in the hope of deflecting the present preposterous pprune pedants)
I doubt very much it was a transmission/reception error on the BUS since that almost certainly has CRC error detection.
The sensor is an analog device and there will be an A to D converter at some stage.
A bad bit within the AD converter data path seems a distinct possibility.
It's somewhere inside the system, perhaps, as you suggested, it's in the AD converter. The replaced AOA vane had been sent to Florida by Indonesian Investigator for analysis and diagnostic. It will be interesting if it turns out there's nothing wrong with the vane.
..
Found on pp. 7/8/9 of NTSC's Preliminary Report
Looking back to that AC and its symptoms, problems seemed to have revolved around the same area the whole time, albeit it had gotten progressively worse up until that fateful flight when
ALL indicators found completely unreliable.