Originally Posted by
Loose rivets
Now to another issue in the Herald's list. They go back to the black box taking in good AoA data and corrupting it - in both if not all, cases. Certainly, the chance failure of three vanes stretches the old credulity, though the balance weight hypothesis in the ET flight is very compelling. But along a pure logic line, I would have looked very carefully at the prior reports - in addition to the three major vane issues. The more I read the more I'm not satisfied the Herald's suggestion is not correct. It leaves me with a deep concern about what I've described as a ghost in the machine.
Apart from the digital errors fitting nicely with the three vane positions - they take the very rapid change of angle as being more electronic than a pendulous swing. But as I say, the latter is good fault modelling. It's just that slight angle change from a long steady error state, to a slightly different long steady state. That's odd.
There were
not 3 separate 3 AoA issues, the last 2 Lion Air flights had the same AoA sensor with exact same offset. The AoA sensor had been replaced before as a troubleshooting measure but we still have no facts on the returned units condition.
As to the slight change in steady state in ET trace:
The first significant) downward bump in vertical G was at 05:41:15 coincident with the change. Assuming the AoA (sans vane) sensor was wedged at a limit (bird innards even) it was jostled and settled slightly lower.
I don't really understand the drive to make both instances have the same cause since the traces are totally different.
Both Lion air flights had an active AoA with a fixed offset. This 'might' be electronics but could also be explained by a mechanical issue.
ET had a sudden swing to full scale and then tracked G at the end. The speed of the initial swing is hard to read from the graph but does not look faster than the random variations on the working unit.