bimmerdriver

Would you have us believe that 737s have AoA sensors for no reason? If so, that's a lot harder to believe then they are on the aircraft for a specific reason.

WildcatYXU

They are absolutely not the same. Every other automation can be overridden by a pilot and most of them are shut down if erroneous signals are detected.

canopus27

First off, let me say how much I appreciate that we're able to have a reasoned discussion about this, without slipping into the sort of invective that is oh-too-common in many online debates today. You & I may end up agreeing to disagree, but that's the nature of a debate.

You've quoted Juan Brown pretty extensively in this thread, and I'm not sure why. He has an opinion and a youtube channel, so good for him , and I'm always willing to listen to logical arguments - but just because "Juan Brown said it", doesn't carry any specifically additional weight for me.

For me, I have been following the pprune discussion on this topic pretty closely. pprune is not immune from random self-described experts nor hyperbole either ... but if you follow the discussion there, you can get a sense of what the broader pilot community is thinking. Much like FT, there is always a mix of opinions, and it's up to the reader to decide which ones carry more weight.

You've already lost me here. First of all, there's no reference in the runaway trim procedure to airspeed at all.

Secondly, it's really not clear to me that the pilots did not control their airpseed. They were dealing with stall warnings, and they were trying but failing to climb, and so they let their speed increase to Vmo ... but once at Vmo the speed stabilised and did not continue to increase. This is not a description of uncontrolled airspeed.

Next, you comment that "they also took a long time to turn off MCAS". First, I'll observe that there is no "MCAS" switch available; the only option is to cutout the entire stab trim system - but they clearly shouldn't do that right away, as the above checklist makes it clear that step two is to control the airplane pitch with electric trim! So they tried that, the runaway continued, and then they cut-off the stab trim as directed by step 5. Seriously, how could anyone expect them to do these actions differently? I'll remind you that the default 737 MAX system configuration does not provide an indicator to the pilots saying "WARNING: MCAS is trying to kill you".

Yes, they turned the stab trim back on after several minutes of trying but failing to adjust the trim manually. Once again, there is no separate switch for MCAS, so for you to say that they intentionally turned the MCAS back on is a bit of a stretch. They knew they were out of trim, and they were trying to control that trim. Seems reasonable to me.

I'm not sure why you bring race into the discussion. Let's keep this civil and leave that out of it, ok?

I have not been claiming that the pilots are perfect - and to make a mistake is to be human. The problem that I have is that aircraft are meant to be designed to be flown by those very same fallible humans, and so the fundamentals of an aircraft design should allow for normal human behaviour. Of course there are incidents where the primary cause of a crash is the pilot behaviour, I'm not claiming otherwise - but it's way too easy to just blame the pilots in every case, and it's not reasonable to expect the pilots to have a perfect reaction time every time. The plane design should incorporate that.

After Air France 447 was flown into the ocean, after the CVR was recovered one of the first responses was to send all Air France pilots back into the simulator for remedial stall training. I don't thik anyone disputes that the overall situation in that flight was otherwise recoverable, and the pilots (specifically the relief pilot) were to blame for the crash.

We've now had two MAX's crash in very similar circumstances, and the pilots were clearly not the primary cause. I think a deep dive into "was this particular pilots reaction perfectly optimal" is the wrong conversation to be had in this case. If even 1% of the pilots who experienced a similar situation, ended up in a smoking hole in the ground, then a conversation about pilot skills and pilot responses is missing the mark.


Yes but .... a plane should be designed such that the complete range of qualified pilots are able to handle it. An argument that "you'll survive only if you're lucky enough to be flown by a pilot who's skills are in the top 5% of all pilots" does not reassure me.

We agree.

PLeblond

As can MCAS, if one follow the procedures detailed in the Emergency Airworthiness Directive 2018-23-51. Had ET properly updated their manuals and training, this could have been avoided. Ironically, had ET done so, the MCAS would most likely not have been improved to include a second AoA sensor and proper improved training, so it looks like flying will be safer after this accident (like after almost every accident).

So maybe the world is in a better place because ET was delinquent in their procedures, as macabre as that may sound.

PLeblond out.

bimmerdriver

I'll touch on a couple of your points. I have some other things to do...

I quote Juan Brown because I've been watching his coverage of the Oroville spillway failure and as an engineer, I find him to be a thoughtful and credible person. YMMV.

When MCAS fails, it takes over the trim, this is basically the same thing as runaway trim, although the underlying mechanism isn't exactly the same. If there are trim problems, the runaway trim checklist says to open the breakers. The AD after the Lion air crash also treats MCAS in the same manner as runaway trim. Nowhere does the runaway trim checklist or the AD say to close the breakers after they were initially opened. The runaway trim and AD also say to disable the autothrottle. When the autothrottle is off, it's the pilots responsibility to maintain a safe airspeed. They did not touch the throttles, resulting in the speed steadily increasing to Vmo eventually the point of overspeed warnings. If that's your idea of controlling airspeed, you and I have a different viewpoint. Despite MCAS being slightly different than runaway trim, the procedure to handle them is virtually the same.

I did not originally bring up the topic of the pilots nationality or ethnicity. I don't know what it is. All I know is that they work for an African airline. Others have brought up a comparison of "north american" and "third-world" pilots and I reject that. Pilots should be trained to the same standard, irrespective of what airline they work on, but to deny that some third world airlines have dubious safety records is not rational.

I'm not sure where you get the idea that a pilot would have to be in the top 5% of pilots to get out of this situation. I understand that every 737 pilot is trained to handle runaway trim, so IMO, every 737 pilot should be able to handle runaway trim. If not, what's the point of the training? Also, JB talks about how every pilot should revert to memory of acceptable power settings for every pitch condition in the event of automation failure. I do not think these pilots did that. If we disagree, so be it.

yulred

WildcatYXU

No, MCAS by itself cannot be disabled. The AD you've posted requires to disable the aircraft's electric trim system completely. It is a procedure that works, but it may open another can of very stinky worms. If there would be a MCAS switch in the cockpit, both JT610 and ET302 would be most likely known only to Aviation Herald's readers as flights that had to return to origin due to AoA sensor failure. But there is no such thing. And it is better you're out as we can do without personal attacks.

J. Leslie

bimmerdriver

The cut-out breakers disable MCAS and all automatic trim, including speed trim. The procedure is basically the same as for runaway trim. When the breakers are opened, the trim wheels are used. Not sure why you claim that's a "very stinky can of worms".

WildcatYXU

For example a situation when the crew finds itself flying a severely mis-trimmed aircraft close to the ground, pulling on the yoke with all their might and no electric trim available. The manual trim wheel is impossible to move due the load on the stab and you have no altitude available to unload the stab. I believe this stinks pretty badly.

A video how a mis-trim situation looks like is here.
Please note that the pilots in this NG simulator started out at 4 units AND and got only as far as 2.5 units AND when manually trimming nose down. They weren't able to trim it back up.

ridefar

I wouldn't have us believe anything, and I don't have the slightest clue what they are for. The difference is I am not making stuff up and posting like I know what I am talking about. You are. Without any evidence whatsoever. It is awful. Please stop.

The Lev

Have you ever experienced a go-round? It take about 15-20 minutes for the pilots to go around, properly align with the runway and land. Now imagine trying to do that with a severely out of trim aircraft. It's not like you are walking down the street and you simply turnaround and retrace your steps.

Can you point to where in the preliminary report or elsewhere it says that ET hadn't properly updated their manuals and training; or is that just wild speculation on your part? Everything I've seen says the pilots were aware of this EAD.
https://www.thenational.ae/business/...-says-1.839869

This has been explained by various people. I suggest you watch the video posted by @wilcatYXU

Bohemian1

Since many seem interested in the AOA sensor, here's a related story abut similar consequences from a faulty sensor, but for a different aircraft.

While MCAS may be unique to this aircraft, similar systems exist elsewhere.

ridefar

Not to mention that if they had a full load of fuel and it was at altitude they have not have been able to "just" land, and might have had to dump fuel. But that would spoil the blissfully ignorant narrative couched in authoritative language of the OP.

PLeblond

Here: Crash: Ethiopian B38M near Bishoftu on Mar 10th 2019, impacted terrain after departure

On Apr 11th 2019 The Aviation Herald received a full copy of the Flight Operations Manual (FOM), Revision 18B released on Nov 30th 2018, which is currently being used by Ethiopian Airlines (verified in April 2019 to be current). Although Boeing had issued an operator's bulletin on Nov 6th 2018, which was put into Emergency Airworthiness Directive 2018-23-51 dated Nov 7th 2018 requiring the stab trim runaway procedure to be incorporated into the FOM ahead of the sign off of this version of the FOM (the entire document is on file but not available for publishing), there is no trace of such an addition in the entire 699 pages of the FOM.

The article also goes on to say that the ET preliminary report had important gaps in the timeline that leave a number of questions as to what the flight crew were doing. It appears the preliminary report has somewhat selective time lines. Add to that the fact that the FDR & CVR were downloaded in France (no bias there, of course) and according to an article inAviation Week dated March 25th "The U.S. participants in the Ethiopian probe, including FAA, the NTSB, and Boeing, have not been allowed to analyze ET302’s flight-data recorder data, the source with FAA ties said. Access to the critical data has been limited to what amounts to cursory reviews..." one might think that ET is participating in CYA, but I digress.

Bottom line: MCAS is getting an upgrade to make it better and crews will be getting more training (at least the countries and airlines that wish to do so, as this point is controlled by each country...).