[salawat]

Note the penultimate Lion Air flight had a third-pilot dead-heading in the cockpit. Not a regular luxury.

Also, the AoA-vane was replaced with a faulty part, and never retested after install if I recall correctly. A procedure complicated by the fact the plane would have had to have been started, shutdown, then restarted since the Flight Computer switches from side-to-side each flight.

So a maintenance tech may have accidentally tested the wrong computer assuming the documentation wasn't up to snuff. Can't say as I've seen that part of the documentation myself; but considering they left MCAS out of the pilot docs, I somehow doubt that it was greatly elaborated on in the maintenance docs as well.

[magduf]

I think that 3rd pilot was key not just because of an extra person; IIRC, he had a vantage point the pilots didn't have, and saw what was going on with the trim wheels.