> knowing some greedy bunch of assholes were effectively that malevolent entity, whose will was expressed via the aircraft. If this it true then link? When was this confirmed? Who are the assholes? Else this is just Reddit spam that contributes less than nothing.
They would be the set of assholes who: 1) decided to move the engines forward making the aircraft dynamically unstable, but improve performance and potential sales 2) decided to counter the instability with a software system (MCAS) based on a single sensor, with zero redundancy or fail-safe mode, AND make a second sensor an optional extra cost for the airlines, AND bury the whole thing in a poor UI, in short: cheapin…
> "decided to move the engines forward making the aircraft dynamically unstable,"
I don't believe that's true. Per Mentour Pilot, the 737 MAX and the 737 NG are both very stable aircraft that are not prone to stalling[0]. That there is a difference in performance characteristics that creates a difference in how an escape from stall maneuver is to be performed, and the MCAS is meant to paper over that difference.
[0] https://www.youtube.com/watch?v=TlinocVHpzk @16:25 "[...] The 737 MAX and NG are equally less indicative of getting stalled, okay? They are very good, very nicely flying aircraft. But once they're in a thrust stall, they have slightly different characteristics. [...]"
Am I mistaken or is there a missing item in the chronology where the pilots reactivated the electric stabilizer trim? The timeline mentions stab trim being switched to cutout, and if you look at the FDR graphs there's a (relatively) long period of more-or-less stable trim after that. But then there's an automatic trim down, which is only possible if the electric stab trim is switched back on, and there's no mention o…
I find it amazing that there is no mention in the report of this fact. The investigators obviously know that they turned the cutout switches back to normal mode. Assuming there really was no mention of it on the CVR strongly suggests that it was the very inexperienced first officer who did this (the switches are on his side) without getting concurrence from the captain.
If you carefully study the graphs in the report, the plane was really not in bad shape up until this point. They were 7000 feet above ground and climbing. They were going too fast, but again, this is the fault of the crew. If they would have not flipped the cutout switch and taken stock in the situation and backed the throttles down, it is quite possible this flight would have ended very differently.
Per the article a combination of things put them in that situation. Not just MCAS. Why is everyone so wedded to the narrative that this is the fault of MCAS and nothing else? Complex systems that have millions of man hours spent making them safer don't usually have back to back failures because of one faulty subsystem. We've incrementally refined commercial air travel to the point where single source accidents are ba…
It's true there were aggravating factors, like the inability to manually rectify trim, which (would seem to me) would be a aerodynamic or design issue. The point still stands, the root cause was MCAS, without it this would never have happened. MCAS would not have pitched them into a dive, and even if they were pitched into a dive by some non MCAS system, they would have been able to turn on electric trim and recover.…
Yes, Boeing issued this service bulletin after Lion Air: http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC... And the FAA made it an emergency airworthiness directive in response. The steps on it were broadly followed by the Ethiopian flight.
This bulletin notes that electric stabilizer can be used to neutralize the control column prior to STAB CUTOUT, which it appears the Ethiopian crew did not do.
Appears? Where are you reading this to come to that conclusion?
Page 11 of the preliminary report, 05:40:35 "stab trim cut-out".
Page 26, five manual trim up inputs before that time. Manual trim is electric trim instigated with yoke toggle switch.
What is not certain (to me) is if continuous nose up toggle for sure would have inhibited the automatic nose down from MCAS shown at 05:40:45. It really looks like pitch trim still needed to come up more in order to relieve the control column force to bring it back to neutral.
Why didn't they continue to manually trim (electric) after 05:40:35 to relieve yoke back pressure and also to improve climb rate and also reduce speed? I suspect they actually got ahead of themselves, setting trim stab cutoff too soon, not realizing how much more insideous the MCAS upset case is compared to runaway stabilizer trim.
And that is the problem with no training. They had no way to iterate various scenarios of working and failed MCAS behaviors.
Am I mistaken or is there a missing item in the chronology where the pilots reactivated the electric stabilizer trim? The timeline mentions stab trim being switched to cutout, and if you look at the FDR graphs there's a (relatively) long period of more-or-less stable trim after that. But then there's an automatic trim down, which is only possible if the electric stab trim is switched back on, and there's no mention o…
I find it amazing that there is no mention in the report of this fact. The investigators obviously know that they turned the cutout switches back to normal mode. Assuming there really was no mention of it on the CVR strongly suggests that it was the very inexperienced first officer who did this (the switches are on his side) without getting concurrence from the captain. If you carefully study the graphs in the report…
There are a lot of well-taken comments in this thread. However, in reading the Lion crash report and this one, it strikes me that there is a fundamental difference in the crashes. In this case, it appears that the pilots had very little knowledge about the reasons why the anti-stall system was implemented. And their combined flight time on the MAX is absolutely pitiful. In short, normally one thinks of a stall as a low speed event. In this case, by switching to manual with an improperly trimmed plane, it began a process which could be magnified by an accelerated turn (one of the reasons the MACS exists in the first place.) They began executing a rapid 180 degree turn at >300 knots, which is shown on the attitude graph, headed back to the airport. With a heavily loaded plane, is there any reason to doubt this wouldn't induce a high speed stall? The plane became so unstable, as it was outside of its operating envelope, they could not manually trim it. When they used electric trim it turned the anti-stall system back on, and it nose-dived the plane. The Boeing manual and/or directive says once you turn it off, it stays off. If they were unable to manually trim, is it really much of a surprise given their airspeed and rapid turn? So you ultimately see an electric trim which did little to help them, and assured anti-stall would kick in again. The report shows that neither of the pilots had signifcant experience in the MAX. The CVR is replete with ignored overspeed warnings, and stall warnings. An experienced pilot would know the danger is not a low speed stall, but a high speed stall accelerated by a mismanaged turn. By the time they tried to electrically trim it, it was over. Many planes are not aerodynamically stable without computer assistance. This crash is far different from the Lion crash. And I have not seen a single news outlet state the conclusions (or lack thereof) in the report accurately.
> Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT .. Which really under explains the situation. In reality the STAB TRIM CUTOUT must be switched to CUTOUT within 5 seconds of using the electronic stabilizer trim, or the MCAS will re-establish the forces.
Wow. This sub-thread is making the images of the grounded MAXs look a whole lot less like an overabundance of caution. If accurate this failure dynamic sounds more like some nasty boss at the end of an escape room game than standard fault diagnostics.
Yeah, I think that's fairly put. The MCAS system was pretty straightforwardly trying to kill them, and the only way to disable it also disabled their method of recovering from what it was doing.
> The crew performed runaway stabilizer checklist and put the stab trim cutout switch to cutout position and confirmed that the manual trim operation was not working. This is very damning to Boeing. It's precisely the procedure they prescribed and intended to mitigate possible MCAS caused trim runaway. In light of the fact that they put this in place as a justification for moving the engines forward without reclassif…
I'm not versed in the terminologies. What I understood was told previously is that In similar condition (nose down) in other plane just pulling the stick would work but with MCAS you have shut it down using some switch and just the stick won't work. And now the report is saying even that switch doesn't work? That one MCAS goes bonkers there's essentially no recourse?
The switch works to disable MCAS, but at the cost of also disabling the trim motor, which is what you need to use to recover from what MCAS was doing before you disabled it.
Are there any airliners from any manufacturer where the pilot always has enough authority to override full trim?
Airbus just gives you a joystick with no force feedback at all. So yes ... but an entirely different philosophy. You tell the aircraft what you want it to do and it figures out how to do it. I suppose these recent events could be used as an argument against the idea of doing essentially fly by wire but then putting in a whole lot of extra stuff to make it seem that you are not doing fly by wire.
No, on Airbus the joystick still only moves the elevator, which has less control authority than the stabilizer, which is what trim controls.
This bulletin notes that electric stabilizer can be used to neutralize the control column prior to STAB CUTOUT, which it appears the Ethiopian crew did not do.
Appears? Where are you reading this to come to that conclusion? Page 11 of the preliminary report, 05:40:35 "stab trim cut-out". Page 26, five manual trim up inputs before that time. Manual trim is electric trim instigated with yoke toggle switch. What is not certain (to me) is if continuous nose up toggle for sure would have inhibited the automatic nose down from MCAS shown at 05:40:45. It really looks like pitch tr…
It seems the "yo-yo manoeuvre" required to manually trim when severely mistrimmed with deflected elevator stopped being taught or mentioned in Boeing manuals decades ago.