The A3320 was designed from scratch as fly by wire…it looks like they are introducing fly by wire into an old design. Having only one AoA vane sensor as basis for computing the STAB trim position used to handle the bigger engines hence thrust changes impacting the stab position…seems an interesting approach? Are the crews indeed trained enough to identify a stab trim runaway situation…in case the flight control software goes TU? I think a lot of interesting questions…Stab trim runaway has been an old issue in Boeing aircraft after this sabena 707 crash all Boeings had stab trim cut out switches installed …..
https://aviation-safety.net/database/record.php?id=19610215-3&lang=nl
hence the discussion is alive again it seems..
https://www.nytimes.com/interactive/2018/11/16/world/asia/lion-air-crash-cockpit.html
@RobertL18C yes I saw that article last week apparently the FAA/Beoing debate was very heated in recent months before Éthiopia accident: can you claim that you have the same physics by having the same user interface & parameter inputs/outputs?
This has been stretched a bit in recent Boeing upgrades to 787/777 and 737M/8, that is probably true for engineers/pilots but the press and markets seem to disagree (a self diving truck is not the same self driving tesla altough the control feel the same as scrolling an iPad screen and the same physics apply)
There was an interview with a Norwegian (NAS) high up technical person something about this. What he said, I got the impression that it was a matter of pilot training. Like a problem that really isn’t a problem unless you have no clue what you are doing. It was on TV, no details of course, but that’s the impression I got.
LeSving wrote:
Like a problem that really isn’t a problem unless you have no clue what you are doing.
Seen many times. There’s possibility that not understanding what automation is doing (or doing wrong) can lead to problem.
LeSving wrote:
Like a problem that really isn’t a problem unless you have no clue what you are doing.
A more correct way of putting it is unless you have no clue what the aircraft is doing because you have not been told.
A similar thing most likely caused the Scandinavian Airlines MD-81 twin engine failure in 1991.
Airborne_Again wrote:
A more correct way of putting it is unless you have no clue what the aircraft is doing because you have not been told.
Probably more correct, yes. He also said they followed recommendations/info from Boeing, and I would think that everyone using those planes received the same info? Also, logically, if there were something really wrong with these planes, Boeing would put them on the ground after these accidents. Since they don’t, it is reasonable to believe this is a thing that already has been dealt with and fixed ?
We’ll have the answer soon as boxes have been found… The question is, if it’s not the AoA issue, what else…
They have already been recovered.
I think blaming the crews is too easy. Even if Lionair should have seen that an airplane which had problems all over before the accident, nobody expects this kind of thing. And what good does an “assistant” system do which under the wrong conditions crashes the plane? Nothing in my book. Particularly if you don’t tell the pilots how it works until they find they can’t control it.
In the Lion Air case, all they would have had to do to regain control is to lower flaps or to engage the AP. But they did not and could not know that.
What happened here is still a big mystery but it won’t be much longer. If it is the same thing however, then something has to happen darn bloody fast.
I can understand any airline CEO who grounds the Max Fleet until it is clear what happened. And I can understand CAA’s who do the same under the circumstances. Not to forget the fact that the press is exercising huge pressure.
From an engineering magazine I just read, a much more detailed and, well – technical version of this is found.
Boeing is in the process of updating the software for the MCAS. Updates will come in the coming weeks. Boeing has since long made changes in the FCOM (flight crew operations manual). It is described how the pilots should deal with cases where one single measurement is erroneous. The MCAS can also be overridden manually, using both electrical and manual trim (don’t know what’s the difference, but that’s what the article say).
Both FAA and EASA have in November last year ordered all companies using the MAX to update the manuals describing these issues, and how the pilots should handle it.
