shadowspar

I don't think your concern is unreasonable, but one thing I'm bearing in mind as someone who has two 7M8 flights coming up themselves - one of the key issues with the Lion Air crash was the pilots being unaware of MCAS, its behaviour, and most importantly how to lock it out. I have great faith that Air Canada's 7M8 pilots are keenly aware of those things now.

meagicano

This is my thought. I just went to check in for AC460 for tomorrow - it was supposed to be an E90, but the 7M8 seat chart popped up, so it looks like it's been upgauged. I'm finding the concerns around the 7M8 a bit concerning, but I have faith in the AC pilots and will just deal with it instead of trying to switch up my flight plans. I would feel a lot differently if I was flying this bird on a low cost carrier.

Stranger

Maybe. But then I am sure some folks here will jump at this and remind you of the SFO incident...

More to the point, there is currently a high degree of awareness on the issue.

Or from a different perspective, taking a flight knowing that the safety level is not 2018 but 1988, would you pay a change fee, or live with the odds? You would have flown in 1988 probably...

Still given a choice I would probably book on an aging 320 instead. And I submit if most people would, that would help sending the message that a sensible permanent solution id needed. I don't have much faith in the capability of the AC management to grasp the seriousness of the issue.

YEG_SE4Life

You and I don't disagree often. However, with due respect, I really think this statement is a little over the top. There is no doubt that, with the current accident, they are at least as capable as any of us!
What we don't know yet is, why this plane? Is there something different about it? I have been on a 7M8 many times. I have never noticed the nose suddenly pitching downward.

Stranger

Speaking as an engineer here.

I tried to make my case in an earlier article. My argument is that as the plane is currently designed, it is fundamentally flawed, and that the only acceptable remedy would be to redesign the horizontal stabilizer to make the design unconditionally stable throughout the operating envelope, and retrofit the entire fleet.

However AC management is dominated by finance and marketing people, with no one with engineering background until very far down the totem pole, hence no grasp of the issue. So that at the end of the day, priority will be to keep these planes in the air, no matter how flawed they may be.

Furthermore, if you read discussions among pilots on the issue, while there is a degree of alarm, alas it ends up on bolts and nuts stuff about the band aid solution that Boeing came up with, with no grasp of the bigger picture, unfortunately. I imagine the situation will be the same at AC. Hopefully certification authorities may step in, but nowadays they are midgets compared with plane manufacturers.

expert7700

I agree, I'll be avoiding the MAX whenever possible.
I think it's noteworthy that the same 737max part implicated in Lionair have failed at least twice on a North-american carriers 737max.

from airliners.net user patplan:
During the three weeks before Lion Air Flight 610 plunged into waters off Indonesia, Southwest Airlines Co. replaced two malfunctioning flight-control sensors of the same (737max) type that has been publicly implicated in the crash, according to a summary of Southwest maintenance records reviewed by The Wall Street Journal.

https://www.wsj.com/articles/southwest-replaced-flight-control-sensors-of-the-kind-implicated-in-lion-air-crash-1542330689

eigenvector

What is concerning to me is that the issue, which could have been mitigated had Boeing disclosed it to operators, has been brought to everyone's attention only because 189 people died.

What other undocumented behaviours exist in this aircraft that pilots are not aware of?

canopus27

Why this plane?

Well I need to start with the obvious caveat that no one will actually know until the formal investigation is complete ... but the speculation goes like this:

A terrifying incident Report: Thomsonfly B733 at Bournemouth on Sep 23rd 2007, disconnected autothrottle on approach results in 44 degrees pitch up occurred in a much older 737-300 in 2007. The quick summary is that it got into a deep stall during approach, and as the pilots tried to power out of it the underslung engines simply caused the plane to pitch up even more. The pilots eventually did recover, but not before the AoA got to 44(!) degrees.

The 737-MAX has even larger engines that the above 737, that are more powerful, and located even further forward. As a result, during certification of the MAX the FAA deemed that the likelihood of pitch-up problems such as the above was too severe, and so they required Boeing address it.

The observation that @Stranger made, really relates to how Boeing responded. Instead of going back through a more comprehensive (but expensive) re-design, Boeing instead added a software only fix - the MCAS. Personally, I think that the fact Boeing did not tell even the airlines/pilots about this fix, is indicative of the fact that even Boeing know that it's a hack.

Then, further compounding the situation, the MCAS (which is driven off the AoA) appears to only gather data from one AoA sensor. Based on the reports, it does not appear to average the L & R sensors, nor does it appear to do any additional sanity checking on the data. Thus, a single failed AoA sensor (as seems to have occurred in the incident flight) could be enough to trigger the problem.

So yes, there needs to be a problem with the AoA sensor before there's an issue .... but the fact is that this entire system was only installed as a bug fix (vs an integrated system that was planned from the outset). And (to answer your question) the "bug fix" was only required on the MAX, because it's an old design that Boeing have tried to stretch the life of.

YEG_SE4Life

My question wasn't with regards to the model. It was specific to the A/C. Why did this particular A/C have a problem with pitch control? If, in fact, this is actually determined to be the cause of the crash.

It appears that the 7M8 model has logged many hours without an apparent issue (that we know about), but this A/C appears to have had problems early in its life.

Why? Is their something unique about the configuration? Was it a malfunction, that you may find in a series of models?

Obviously there is reason to be concerned if, in fact, this plane crashed because the pilots lost control, and other planes exist, with the same condition that would cause the pilots to lose control.

There is nothing wrong with passengers jumping to their own conclusions, when booking flights. However, for any one of us to believe that we know better than the engineers and AMEs who specialize in this area and who have more information than the bits and pieces released to the public, I'm not sure it's correct to jump to conclusions.

Obviously, in the short term, it is incumbent on the airline to ensure their planes are safe, if they continue to fly them. The Directors at Boeing have a fiduciary duty to ensure that as well. I doubt anyone is taking this lightly.

it is interesting to read FT. If AC has a near miss at SFO, that is because AC has a poor safety culture. If another airline has an incident, well, AC is unsafe.

ridefar

I am not saying AC is unsafe, I am choosing to minimize my risk. My risk on a AC 737Max may be pretty darn low. But at this point it appears that it is higher than other, non-Max alternatives.

Stranger

Hold on. Not saying AC is unsafe at all.

In the Lionair case, because one AOA sensor gave incorrect information, the MCAS fix in effect made the plane crash. Admittedly the pilot might have taken corrective action, but they are not gods and they had been left in the dark. Why only that case? Because obviously the sensor does not fail every day, and in other instances, pilots were able to deal with the issue.

But my point remains, the MCAS "solution" is inherently flawed, at a very fundamental level. And a true solution will be painful and expensive, and "very bad" for all parties. But I am trying to argue that it is needed.

As to fiduciary duty, the lawyers etc, I believe the AC folks are quite safe. At this time nobody is expected to know more than Boeing, unfortunately. Not airlines, and it seems, not even certification authorities. And no, I am not really blaming them. And I am not among those who consistently question the AC safety culture, even if I occasionally have doubt (remember the Klaus guy).

(And BTW, you probably can replace AC in my argument by many other first rate airlines. Hopefully not all of them, though.)

As to believing we know better than engineers and AMEs at these airlines, yes I believe some of us engineers definitely should know better than AMEs and pilots. As to engineers at AC, to me they look like they are too far down the totem pole to feel they can make their voice heard too strongly. And since a true solution is going to be very painful and costly, higher up is not going to like the message anyway, and will rather prefer to indulge in wishful thinking and let Boeing reassure them that the band aid is OK. In the meantime the 7M8 is still not supposed to be a fighter jet...

canopus27

Gotcha.

From what I've read, a suspect AoA sensor was replaced just prior to the incident flight. That tells me that the problem was not the sensor, but some part of the connected system; perhaps as simple as a failed or chaffed wiring bundle.

But the problem is that "stuff fails". Whether this incident was caused by the wiring bundle, or a lose connector, or a failed computer module, or something else ... stuff is going to fail. The system as a whole should be designed to be resilient, so that the failure of a single component does not cause the plane to fall out of the sky.

Thus, my concern is not that there was a problem with this sensor, somewhere in the stack. My concern is with the model - because the system as a whole appears to be susceptible to overall failure as a consequence of a single failure. That's not a good thing - and it does lead me to wonder whether other single points of failure were also allowed to slip into the model.

Well yes, of course!

YEG_SE4Life

In the case of the Dreamliner, did the regulators not show that, if they believe there are inherent problems, they are not afraid to ground a plane? And didn't they do this, despite the fact that there was no accident? I'm actually truly asking these questions.

Stranger

There were a number of fires, which could have been quite dangerous if they would have happened in flight instead of on the ground.

Plus, the lithium batteries and how to deal with certification had been an issue from early on.

YEG_SE4Life

The only reason I asked is because, in the SFO thread, folks suggest that they won't react until there are fatalities. However, the real point is that they do react when they believe that there is an inherent issue.
I still think that folks have the right to make their own decisions and can't really fault anyone who decides one way or the other, on the 7M8. I am still flying on board them. I will be happier when they are enabled.