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Lion Air crash: Investigators say plane was 'not airworthy'

bbc.com

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Re: Lion Air crash: Investigators say plane was 'not airworthy'

#11

Post by mnw21cam »

Preliminary report: https://www.flightradar24.com/blog/wp-content/uploads/2018/1...

As far as I can tell, one of the angle of attack sensors failed on the previous flight, the aircraft started to continuously trim nose down, the pilots trimmed it back up again a few times before switching off the automatic trim motors, declaring PAN-PAN, and continuing the flight. They reported the fault, the engineers "fixed" the wrong thing, and on the fatal flight it started playing up again. Except this time, the pilots didn't switch off the automatic trim motors, but just kept re-trimming nose up to counter the continuous automatic trim nose down. Eventually they got overwhelmed and crashed.

It's a tragic accident, and blame can be spread all round. It's good that the previous flight were able to work it out, and terrible that the fault wasn't properly fixed, and the subsequent flight didn't work it out. Also, that the aircraft wasn't resistant to this particular fault.

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#12

Post by mnw21cam »

thesimon wrote: post #9
qarioz wrote: post #7

Earlier quoted context omitted.

No, you need certification to be able to fly eact plane type, which equal to 6 months retraining. For this incident Boeing "forgot" to tell companies do not do what you usually do, as it doing what you do actually worsen the situation. Boeing released emergency notice after that incident, and data from black box showed that the pilot is doing precisely what they are used to do. Plane it self is legal to fly at that t…

But isn't moving "STAB TRIM" to CUT OUT a memory item even in the 737 NG in the case of a trim runaway?

Yes. The newfangled plane had a new way for trim runaway to occur, but the action to take in the event of trim runaway shouldn't be (AFAICT) any different. They managed it on the previous flight.

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#13

Post by _archon_ »

davidhyde wrote: post #5
amelius wrote: post #3

Earlier quoted context omitted.

From the article: > The findings by the National Transport Safety Committee (KNKT) suggest that Lion Air put the plane back into service despite it having had problems on earlier flights. Seems this implies there are at least two parties involved: airline and aircraft manufacturer.

Let's also not forget the pilot. They are supposed to read the manual so they can respond to a badly behaving auto pilot / guidance system. There is always a pilot override. I guess you can bundle that in to airline blame though (lack of training or bad org structure). But really, this is a new plane and Boeing probably don't have adequate software testing in place for the newly written / ported software.

The FAA issued a mandatory airworthiness directive as a result of this crash. Boeing didn't include training for a new anti-stall automation regime in their type cert update class for existing 737-rated pilots moving to the 737 MAX. There was apparently a malfunctioning angle of attack sensor, which caused a software data conflict which caused the anti-stall assist (which the pilot wouldn't have known existed) to repeatedly trim the aircraft nose-down.

There is also the possibility that a separate pilot assist system read a possible near-stall and enforced difficulty in pulling back on the stick (to prevent what it saw as a potential stall). So the pilot couldn't pull out of the dive that the MCAS (trim changer) had caused.

The blame for this incident does not lie on the pilots failing to RTFM. Boeing changed several systems without telling anyone. Now the plane's been type rated, so software changes to fix it are significantly difficult.

Imagine Boeing as a guy saying "Screw those idiots who operate our multimillion dollar safety-critical product; they're too stupid to know how to work it!" This is a closer perspective to the truth than the parent's comment.

Mentour pilot overview: https://www.youtube.com/watch?v=zfQW0upkVus FAA Emergency Airworthiness Directive: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/...

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#14

Post by _archon_ »

unionemployee wrote: post #8

For a time, I instructed airline pilots in simulators. The aircraft I taught had a similar mechanism with a "cutout switch" like this Boeing. Often, even when they knew it was coming, the pilots would fail to immediately shut down the system when given a related emergency situation, similar to this one. After learning more about this crash, I immediately thought of the tens of times I've seen this happen in the simul…

If the aircraft were being piloted manually, this crash wouldn't have happened. The increasing imposition of automation and removing the pilot from the equation was the cause of this crash. Your recommendation is to take this further, rapidly?

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#15

Post by nasredin »

mnw21cam wrote: post #11

Preliminary report: https://www.flightradar24.com/blog/wp-content/uploads/2018/1... As far as I can tell, one of the angle of attack sensors failed on the previous flight, the aircraft started to continuously trim nose down, the pilots trimmed it back up again a few times before switching off the automatic trim motors, declaring PAN-PAN, and continuing the flight. They reported the fault, the engineers "fixed" the wr…

Sad.

One pilot was able to figure out the problem, find the solution and land safely. The next pilot did not and hundreds died.

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#16

Post by lmm »

unionemployee wrote: post #8

For a time, I instructed airline pilots in simulators. The aircraft I taught had a similar mechanism with a "cutout switch" like this Boeing. Often, even when they knew it was coming, the pilots would fail to immediately shut down the system when given a related emergency situation, similar to this one. After learning more about this crash, I immediately thought of the tens of times I've seen this happen in the simul…

Trying to "remove the pilot from the equation" is exactly what caused this crash, by giving primacy to this automatic trim adjustment system over the pilot's control inputs. We need to design systems that are more respectful of the pilot's input (in particular, that respond to the pilot's obvious intent rather than requiring the pilot to use some unusual cutout switch to achieve the most basic aeroplane functionality of: push stick forward => pitch down and vice versa).

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#17

Post by mannykannot »

londons_explore wrote: post #2

I like the way the news media tries to point at just one party to blame for any incident, and argues about which party should be to blame, when, like any incident, it was probably caused by tens of coinciding factors, and 'blame' really ought to be apportioned to all parties involved.

This is not the news media trying to point at just one party, it is the reporting of Boeing doing so in order to deflect the criticism that has been directed towards it. US pilot's unions are divided over whether they think Boeing made a serious error in not disclosing the existence of the new system in question, but the fact that many pilots apparently think it was an error counts for something - in addition to actually flying aircraft, professional pilots are our safety watchdogs.

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#18

Post by erdeszt »

_archon_ wrote: post #14
unionemployee wrote: post #8

For a time, I instructed airline pilots in simulators. The aircraft I taught had a similar mechanism with a "cutout switch" like this Boeing. Often, even when they knew it was coming, the pilots would fail to immediately shut down the system when given a related emergency situation, similar to this one. After learning more about this crash, I immediately thought of the tens of times I've seen this happen in the simul…

If the aircraft were being piloted manually, this crash wouldn't have happened. The increasing imposition of automation and removing the pilot from the equation was the cause of this crash. Your recommendation is to take this further, rapidly?

First of all he said little by little so calling it rapid is a bit misleading. Second this was not ultimately a hardware/software failure but the failure of the overall supervisor of the system(= pilot). We can't (yet) make hardwares that are immune to failure but we have redundancy and procedures to deal with these failures. It seems like in this case the procedures were not properly executed which lead to the tragedy. To also address @lmm's point: the leading cause for aircraft accidents are human error and not hardware/software failure so more automation = less accidents. Edit: after reading some more on the subject it seems like boeing share some of the blame for not including the new system(or system changes) in their training program which is again a human error.

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#19

Post by dsfyu404ed »

>"In our opinion, the plane was no longer airworthy and it should not have continued," he said. The committee's report itself, though, does not spell out that conclusion.

Well that's kind of a useless conclusion without the report having anything to back it up. It's really easy to pat yourself on the back and say "yup, wasn't air/road/sea-worthy" in hindsight after there's been an accident.

>Pilots tried to correct this by pointing the nose higher, until the system pushed it down again. This happened more than 20 times. It is unclear why the pilots did not employ procedures to disable the automated system.

This is the million dollar question. Why didn't the pilots turn off the system and fly in "legacy mode" like they would if they were flying the prior revision of the 737.

Re: Lion Air crash: Investigators say plane was 'not airworthy'

#20

Post by cm2187 »

mnw21cam wrote: post #11

Preliminary report: https://www.flightradar24.com/blog/wp-content/uploads/2018/1... As far as I can tell, one of the angle of attack sensors failed on the previous flight, the aircraft started to continuously trim nose down, the pilots trimmed it back up again a few times before switching off the automatic trim motors, declaring PAN-PAN, and continuing the flight. They reported the fault, the engineers "fixed" the wr…

Maybe I am confused, but it doesn't look from what I read in articles that the crash was caused by the problems that made the plane not "airworthy". If that's the case, it certainly needs to be flagged. But I don't get why that makes the headline.
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