Originally Posted by
infrequentflyer789
(a) we don't actually know that the AOA vane itself was the issue on LionAir (or ET, although there is more evidence of a vane failure mode in that case)
(b) if you are troubleshooting a problem persisting over several flights (AOA issues did not start with the replaced sensor) do you assume the cause is the part you have replaced with new, or that the cause is more likely elsewhere?
Indeed the AOA issues didn't start after replacing it, there were some faults reported by the OMF system on two previous occasions, that's why they replaced it. But the stick shaker simptom started after they replaced it. And apparently the OMF system didn't report any more problems with the AOA after replacing it, the pilots didn't report any problems that would directly suggest AOA issues either, so the engineers didn't look into it further between the last two flights.
But the bigger problem with the theory that better reporting would help (I think) is that maintenance appear to have their own automation dependency problem. The Lion Air guys asked the aircraft (BITE/IFIM) what was broken, fixed that and asked the aircraft if everything was now OK, got a yes = job done, end of thinking.
Actually, no, they didn't stop after the aircraft said everything was OK. If they did that, they wouldn't have replaced the AOA vane. Instead they noted that the AOA issues were repetitive, and even as the self diagnosis systems said everything was fine, they replaced the vane because the maintenance manual required doing that in case of repetitive issues. You could claim they relied too much on their manuals, but I don't think that's necessarily a bad thing.
For a more detailed actual example of why reporting stick shaker would make sod-all difference to the outcome, consider this result of a busted AOA sensor:
[...]
Yes, reporting the stick shaker may not have saved the next Lion Air flight. But if there was, let's say, a 25% chance it could have saved it, wouldn't you say it would have been a good idea to report it? If you report the exact symptoms to your doctor they may still misdiagnose you. But why would you make the doctor's job harder by not telling him all the symptoms?
And, again, the actions taken by Lion Air after the accident confirm that the pilot reports could have been better. Otherwise one of their safety actions as a result of the accident wouldn't have been "instruct all pilots to fill the AFML report with as much details as deem necessary to
provide a full comprehensive description of the technical defect to the engineering team. This measure should be applied with immediate effect."
Note that I suggest working out which incident that was before whining about inexperienced or third-world crews or airlines or maintenance...
Actually most of my whining so far has been about Boeing and the FAA, and I think most of the focus should be on them. In my opinion their initial actions, and especially their attitude after the accidents, were appalling. Fighting tooth and nail to prevent the grounding and trying to shift as much blame as possible on the foreign pilots and minimize their own contribution to the accidents was disgusting.
My initial post about not reporting the stick shaker was a reply to yoko1 that said, if I remember correctly, that the crew from the accident flights didn't do a good job, and that the Lion Air crew that saved the aircraft did a great job. In my reply I was pointing out that in fact all 3 crews did things that many posters, maybe including him, would consider questionable, and I provided examples.
What I was trying to convey was that what saved the previous Lion Air flight may not have been just good crew decisions, but also an element of luck. For example, what people may regard as a mistake, enabling the auto-pilot with the stick shaker active, actually bought them time and allowed them to gain altitude. The A/P remained enabled for about a minute. If they didn't enable it they would have experienced MCAS earlier and at a lower altitude, and they may have very well crashed that aircraft.
I agree that we focus too much on the pilot actions. It wasn't my intention to derail the thread with the discussion about the pilot reports, and in any case that seems to be a closed issue, the necessary actions seem to have been taken by Lion Air to improve the pilot reports.