Did anyone ground the max after the first crash or was it all in response to the second?
Interesting tidbit: after the second crash, the Ethiopian authorities decided to send the black box to Europe for analysis, apparently not trusting US investigators with the data.
William Langeweische [0] describes lack of airmanship as contributing to the 737 Max crashes and cites another reason for distrust:
"In the case of the Ethiopian investigation, we have an airline and an investigative body that historically have not been able to isolate themselves from the country’s dysfunctional political life."
"After the cockpit voice recorder was dug out of the wreckage, it was shielded from the N.T.S.B. and whisked to Paris. There, for reasons unknown, French accident investigators agreed to download its contents in private onto a drive for an immediate return to Addis Ababa, where the information remains mostly locked away today and has been withheld in full form from any outside observers."
[0] https://www.nytimes.com/2019/09/18/magazine/boeing-737-max-c...
The plane was traveling fast enough that the strain on the air control surfaces meant pilots weren't able to manually trim the plane back into alignment.
The only way to overcome those forces was to use the electronic motors to adjust the alignment of the rear stabilizer trim. However, those motors also are disabled with the stab trim cutoff switches.
After the fact simulations confirmed that such forces could well have prevented manual control.
See prior discussion and news articles here: https://news.ycombinator.com/item?id=19573893 and https://www.seattletimes.com/business/boeing-aerospace/boein...
So I reject the categorical claim they could have recovered with the flip of a switch.
Further to that point, the preliminary report on ET302 shows they did turn stabilizer trim switches to cutoff, and yet they couldn't move trim manually, likely due to mistrim forces. The logical reason why they turned stabilizer trim back on is it was the only way to get electric motor assisted trim to try and get out of the mistrim. But MCAS immediately triggered again resulting in greater than 20 degrees nose down, and negative G forces by the pilots - it was impossible to recover from that. The final act of MCAS, had it been a human pilot, for sure would be considered a saboteur, it's that ridiculous of a reaction under any circumstance, even had the airplane angle of attack been great enough to trigger MCAS it was a gross overreaction, at low altitude, commanding a path steeply below the horizon, and incompatible with survival.
If uncommanded trim motor action is forcing the airplane into a dangerous dive, it's runaway trim. The pilots must have thought it was runaway trim as they were desperately trying to counter it.
> So I reject the categorical claim they could have recovered with the flip of a switch.
But that's what did happen with the previous LA flight that landed safely.
> it was the only way to get electric motor assisted trim to try and get out of the mistrim.
That's right.
> But MCAS immediately triggered again
The electric trim switches override the MCAS.
So why didn't the EA pilots do that override? I don't know, neither do you. We'll have to see what the NTSB report says.
If we stipulate the MCAS system was faulty, that still doesn’t relieve the pilots of responsibility. The Ethiopian copilot only had 300 total flight hours — so it’s fair to say that copilot wasn’t experienced with flying in general, let alone type-specific experience in an airliner. Since the captain would have been flying the airplane, the copilot would have been the one running through the checklists. Airliners require two pilots for a reason; that copilot had no business being right seat in a technologically advanced airplane. Both pilots specifically failed to follow the procedures. First, they didn’t adjust the throttle at all during the event — throttle remained at climb power throughout, secondly, they re-engaged MCAS because while they pulled the horizontal stabilizer trim cutout switches correctly, they failed to realize that they had to use the manual trim wheels since the electric yoke-mounted trim would be inoperative at that point.
Yes, MCAS was deficient, however, 90% of aviation training is learning how to respond when things go wrong. Complaining about one issue while ignoring the other is disingenuous. Good pilots wouldn’t have crashed that plane. There is a reason that airline pilots in the US must have 1500 flight hours before being allowed in the right seat; there is a reason that airliner crashes in the US are so exceedingly rare. The 737 Max incident revealed plenty about Boeing and system design, but it also shined a light on the effects of substandard pilot qualification in places like Indonesia and Ethiopia. Considering the US flew the 737 Max vastly more than anyone else, a broken airplane would have statistically resulted in a US crash, yet the two crashes we did have were with airlines from countries with debatable pilot qualification processes. Attempting to obscure the cockpit voice recorders from public view and giving them to France (home of Airbus it might be added,) means that Ethiopia had something to hide regarding their pilots’ actions. If it was clearly 100% “Boeing’s fault,” then Ethiopia would want all data surrounding the crash to be on the front page of every newspaper if only to bolster their case that their pilots weren’t at fault. But instead, they hide the data. Why hide supposedly exculpatory evidence? Because it wasn’t exculpatory at all.
I get it, MCAS bad. But those passengers would still be alive if it weren’t for bad pilots. Given that Ethiopian Airlines is a crown jewel of the country and a vital marketing tool of the country, it’s clear why they wanted to hide any hint that pilots of the flag carrier were questionable.
> But those passengers would still be alive if it weren’t for bad pilots.
Are you an experienced pilot, intimately familiar with the 737 MAX, or otherwise an aviation expert qualified to be a judge of this?
I can't see how you could make such a statement with any auhtority otherwise, and your profile does not seem to indicate you are.
I am neither, but it has also come to light that Boeing hid MCAS from airlines and pilot training materials, and even hid details from the FAA.
Together with the quick worldwide action by aviation authorities, and the prolonged grounding, even in the US, is enough make this line of reasoning very doubtful.
I am not a pilot, but I worked on the stab trim design for the 757. There are cutoff switches for the stab trim on the console, and their purpose is to stop uncommanded trim movement. They were successfully used on another Lion Air flight to recover from MCAS malfunction.
The electric thumb switches will also override MCAS and can be used to trim the stabilizer back to normal, and then cut off further trim with the cutoff switches. In both incidents the pilots were able to bring the trim back with the thumb switches, multiple times, but it apparently did not occur to them to shut off the trim after doing so.
I'm very interested to see the NTSB report on this.
In the 737-NG you could turn off autotrim and still have electric trimming. This was changed in the 737-MAX, if you turned on electric trimming you'd also turn on MCAS. That change was poorly documented, and at sufficient airspeed you had to rely on electric trimming because the aerodynamic forces on the horizontal stabilizer would be too high to turn the trim wheel manually.
The electric trim switches override MCAS. This is according to Aviation Week, Aug 19, and is consistent with Boeing's bulletins on the matter and with the pitch profile from the flight data recorder - both sets of pilots had overridden MCAS with the electric trim switches in multiple cycles before their crashes.
https://www.ft.com/content/ee4246ea-5729-11e9-91f9-b6515a54c...
Four seconds later — and only 35 seconds after the nose down problem first occurred — the co-pilot suggested they initiate the emergency procedure recommended by Boeing, and disable the MCAS system by flipping switches in the cockpit.
“The pilots diagnosed and executed the procedure within 35 seconds — that’s lightning fast,” said Jason Goldberg, a spokesman for the pilots’ union of American Airlines, one of the biggest US operators of the 737 Max aircraft.
The flight data recorder showed that the pilots had successfully countered the MCAS input more than once with the electric trim switches. In the Lion Air crash, the pilots successfully countered it 25 times. At any one of those times, the pilots could then have turned it off with the cutoff switches. My source is Aviation Week, Aug 19, 2019.
It says: "Electric trim input will stop the automatic nose-down stabilizer movement" on a bulletin Boeing issued on Nov 6, and goes on to say "The only way to stop the cycle is to follow the runaway stabilizer checklist and toggle the console-mounted cutout switches."
This was apparently done by the previous Lion Air flight which encountered the same issue and landed safely.
The Ethiopian Air pilots also successfully used the electric trim switches to override MCAS. After two cycles of that, the pilots did think to throw the cutout switches, but with the nose down. They should have trimmed the plane to normal with the electric switches, then throw the cutout switches.
All according to AW, which I am much more inclined to believe than other reports, until we see the NTSB report.
The cutoff switches are there to deal with trim runaway, and there is training for that.
Is there training for getting out of mistrim at low altitude without the benefit of electric trim? Is there training even for MCAS upset as distinguished from runaway trim? We already know there isn't a way to simulate angle of attack sensor failure induced MCAS upset, in MAX simulators. Exactly how was it demonstrated that MCAS upset looks like runaway trim? And how much faster it commands nose down compared to the typical runaway trim case?
No.
>Is there training even for MCAS upset as distinguished from runaway trim?
No.
Remember, MCAS was dropped from the manual, and not included in the end training pilot's would be exposed to prior to being handed a MAX. It was nowhere in that presentation. That was covered in the 60 minutes expose.
>Exactly how was it demonstrated that MCAS upset looks like runaway trim?
It wasn't. Take a look at the ET302 preliminary crash report. You'll see attached to it the documentation pages from Boeing even remotely related to MCAS. In fact...
https://flightsafety.org/wp-content/uploads/2019/04/Prelimin...
Check Page 30 for the memory item as written. The AD from Lion Air is in there too I think.
Note the condition description explicitly mentions a condition where uncommanded trim is running continuously.
Before the AD issued after the Lion Air crash, no one even knew MCAS was a thing.
The trim system repeatedly coming on and driving the nose down is runaway trim. The pilot already knows he's in trouble because the trim is running, and he's looking at the checklist on how to stop it. And there is the information on how to stop it. Getting hung up on the definition of "continuous" while the plane augers in is something a computer would do, not a human pilot.
Which is why airliners still have human pilots, not computers, in command.
In reply to someone else you posted to the effect that
>if the trim goes uncommanded, that's runaway trim.
If there is anything I did take out of Langewiesche's article, it is that apparently for some subset of the human species, it appears that the mental optimization you and I are capable of connecting naturally (stab runaway on continuous uncommanded trim-reduces to-> stab runaway on any unaccountable trim), is not, in fact, completely natural to everyone.
I've come to realize I have a team member who is one of those people. I have to be very careful with instructions to them, almost like programming. If I handed him that piece of paper, then asked them whether a pulsing trim system demanded that procedure, I'm not willing to stake my life on him getting it. So life being what it is, I have started to take the possibility of someone being of that disposition into account more frequently.
I've been somewhat disappointed at how frequently I run into it. I'm not saying there is anything wrong with those type of people, just that I can't necessarily generalize the capability with enough confidence to be comfortable with the connection not being proven to be made without demonstrable proof in the form of a simulator session or two.
It's just not a given I'm capable of assuming away anymore. I've seen (and even been the unwitting subject of) too many counterexamples, albeit in less than life-threatening conditions.
I certainly couldn't wrap my mind around why they wouldn't have made the mental connection while actually successfully retrimming the plane. After several months of devoting a hell of a lot of mental cycles to meta-cognition though, I've found I have my own corpus of "Oh, what the hell, how did I not make that connection til now?" which has been the result of many years of habit building.
I think I realized this earlier on, but couldn't convincingly articulate it. It came previously from the idea of psychological anchoring, and it's effect on subsequent responses in the presence of priming. It's a fairly well researched phenomena, and network theory also suggests it's a near certainty that this type of inability to grok can happen if mentation is an emergent result of our internetworked mass of neural nets that is the gray stuff between our ears.
It's still one of those fuzzy hunchy sentiments though, so not really something worth writing a paper about.
One failure scenario that can cause runaway trim is mechanical damage that causes an intermittent short circuit which can cause uncommanded trim. "Continuous" or intermittent, you're going to want to cut off the stab trim, as you would any dangerous piece of machinery that is randomly turning itself on and off.
I have a difficult time conceiving of concluding that "the trim is coming on randomly and pointing me at the ground, but since it's not continuous I'll just let it keep doing that rather than turning it off." I'm not a pilot, but I bet my response would be more like "Holeee phuck, wtf is wrong with the trim, it's going to kill us all! Turn it off! Turn it off!"
As I mentioned, I spent 3 years working on the 757 stab trim system for the 757. Although I didn't come up with the idea, the engineers who did said that's exactly why the cutoff switches are clearly labeled and within easy reach. They're for "the stab trim is possessed by demons trying to crash the plane, shut it off NOW!"
Interestingly, the emergency checklist says to turn off the autopilot first, and if that doesn't stop the trim, then shut off the trim. My tendency would be to stop the trim, then turn off the autopilot, and fly manually the rest of the trip.
For example, there was a crash some years ago where the pilots got an air pressure warning. They dug out the checklist, and started following the procedure. They passed out from hypoxia before getting very far through it.
The checklist was then changed so that the #1 item was "put on your oxygen mask". These things are all so obvious in hindsight, but sadly too much gets learned the hard way.
https://www.seattletimes.com/business/boeing-aerospace/newly...
One of the three seasoned test pilots (the civilian one) ended up losing the plane due to a single-event upset cascading to false positive activation of MCAS consistent with the Ethiopian Airlines disaster. I.e. the system activating at non-extreme AoA.
Also, not pulling power was justified due to the malfunction of the AoA sensor resulting in an airspeed unreliable state, the response to which is essentially "set throttles to what they should be for that stage of the flight", which was climb out in Ethiopias case, and from a hot and high airport to boot. They also ran through the procedures written by Boeing to a T. The fact that Boeing intentionally withheld important implementation details from the pilots can't really be used against them. The measure of incompetence is to not know something you absolutely should. The Ethiopian pilots had none of that info, and Lion Air swapped in a garbage part, and had bad paperwork in the logs, and furthermore, we're known to be at risk of "flying by rote" by Boeing. This damns Boeing even more, since they knew of the local minima in terms of safe operating style, yet still left out the information those pilots would have needed to safely fly the plane, ostensibly so as not to draw scrutiny from regulators.
In short, appealing to the need of a master airman to fly a demonstrably physically dangerous (and possibly unairworthy given explicit prescriptive criteria in the FAR's) aircraft doesn't speak volumes to the overall safety of the aircraft, which puts fault squarely in the corner of the manufacturer who self-certified the safety of their design.
Furthermore, with the overspeed and extreme trim, the trim wheel was likely inoperable, or else required so much force that the pilots reasonably thought it was inoperable. Due to the overspeed, the pilots were in an impossible situation where they concluded they needed electronic trim control while also knowing that this system was threatening their demise.
To place blame on the pilots is to plan to fail.
The pilots didn't follow the airspeed unreliable procedure, and oversped the aircraft. Maybe it's the best they could do, but definitely not what they were expected (and trained) to do.
Electric trim is not turned off "when the yoke is pulled" - it's momentarily turned off when electric trim thumb switches on the yoke are pressed.
And they switched it back on because they couldn't manually re-trim due to very high speed that the plane was travelling at that point.
BTW the airplane was a 737 Max, not 737-NG.
I believe the parent's point was that they did what would have made sense in the NG, not realizing it wouldn't have the same result in a Max.
But it was heavily criticised. Just from a cursory reading you can see many cases of subtle and not so subtle language choices that show a heavy bias and a string of one-sided arguments.
HN has this flagged thread, https://news.ycombinator.com/item?id=21004683
Does he consider airmanship lacking in the USAir 427 crash, or in Colgan Air 3407? Both cases pilots pulled back on the yoke the entire time making recovery impossible, exactly contrary to all of their training. He's dismissive of "startle factor" in Air France 447 as well, as in, he doesn't even bring it up or any of the other factors in the final report, he just dings pilots as lacking airmanship.
If true, very serious. Can you provide some references for this as I've not heard of it?
Back in march there was a link to a raw CSV dump of that database here on HN, but I can't find it again...
https://news.ycombinator.com/item?id=19373216
Other news article about it:
https://www.sbs.com.au/news/it-pitched-nose-down-us-pilots-p...