#1 turned off the trim system and continued the flight without incident. (This flight is almost never mentioned, as it doesn't fit the narrative.)

#2 never turned off the trim system and crashed.

At this point, an Emergency Airworthiness Directive was distributed to all MAX pilots instructing them to restore trim with the electric trim switches and then turn it off.

#3 turned off the trim system when it was severely nose down, and crashed.

It was mentioned repeatedly Walter; if not in the articles, then in the comments. The fact remains that afterward, when regulators put more pilots (two military and one civilian trained) pilots into single-event upset simulations, 1 of the three failed to recover the plane in time.

If you acknowledge the training was faulty, then just let it be. Trim runaway presenting continuously vs. intermittently may not seem that important from a clean room engineer's perspective, but when viewed by a pilot through the lens of instruments, blaring alarms, and whatever else is going on in the cockpit, my engineer's optimism favors not relying on the human being perfect, or the defect only happening at a non-terminal part of the flight regime.

It sucks that it played out the way it did. Maybe if someone would have spent as much time on MCAS and the pilot training as you did the 757 auto-trim, it wouldn't have been an issue.

But they didn't. And innocents paid for it.

Without more information on what the background and training of those pilots, and why the one failed, I'm afraid it's just an anecdote.

In both crashes, the trim came on repeatedly and the crews repeatedly brought it back to normal with the electric trim switches. 25 times in the case of the LA crash. They obviously knew that the trim was the problem, because they took this corrective action. The trim running is obvious by the large black&white spinning wheels in the cockpit, and the deliberately loud clacking sound the running trim makes.

All they had to do was then turn it off.

> But they didn't. And innocents paid for it.

That's right, and that's the tragedy.

As to why they didn't, who knows. The stab trim cutoff switch is right there in a priority position on the console, because it's a damned important switch. Dealing with runaway trim is supposed to be a memory item, i.e. memorized.

It does suggest a training problem.

Nobody is blaming the engineers for this. But it is, by design, a bad system, that can by attrition defeat human decisions.

http://airsoc.com/articles/view/id/5d5143c7c4263ce96fd616b6/...

Differen source.

https://aviationweek.com/air-transport/software-fix-will-add...

The civillian trained test pilot lost it. The two military pilots did not.

"In one scenario, the bits chosen first told the computer that MCAS was engaged when it wasn’t. This had the effect of disabling the cut-off switches inside the pilot-control column, which normally stop any uncommanded movement of the horizontal tail if the pilot pulls in the opposite direction."

The cutoff switches cannot be disabled on the airplane.

"They flew the same fault scenario again, this time deliberately allowing the fault to run for some time before responding. This time, one of the three pilots didn’t manage to recover and lost the aircraft."

That's kinda vague.

There it is! Knew it was in SeattleTimes somewhere!

And lookout for the part about disabling cutoff switches, I think Dominic might have written that better, because I think he's talking about a safety function that was removed specifically for the MAX where hauling back hard on the yoke would stop trim commands in progress on NG airframes? MCAS required that that functionality not be ported forward to the MAX.

This isn't disabling those cutouts though. Those are literally, like you said, a hard switch.

>According to a second FAA source, it was the AEG pilot, representing a typical U.S. airline captain, who failed to recover the jet.

There's the bit about the civilian test pilot.

It's a hard switch for good reason. I hate "soft" switches that supposedly disable microphones. Phooey on that.

BTW, on my hotrod I installed a hard switch to shut off the fuel pump, as well as an oil pressure switch that would shut it off. I have a g-switch to cut it off, too, but haven't gotten around to installing it.

So the procedure for runaway trim (turn off electric trim, use hand wheels) doesn't work. You have to instead use electric trim first to get back into normal trim, then turn off the electric trim, and never turn it back on for that flight.

I feel like this isn't talked about enough. I had no idea how bad it can actually get: https://youtu.be/aoNOVlxJmow?t=806

There is some discussion amongst pilots at https://www.pprune.org/tech-log/619326-boeing-advice-aerodyn... which further explains how difficult it can be to manually reduce load on the stabilizer and manually trim the nose up.

With the gear ratios we're talking with by hand actuation, I would not want to have to be one of those pilots.

Aviation rules are written in blood. Training is being updated and fixed. But regardless, MCAS itself is controversial and fallible - it’s crucially important that Boeing make it better.

I.e. they piloted the plane without the MCAS, which they were not trained to do. The whole reason of the existence of the MCAS is to avoid training the pilots to fly the planes without it.

This kind of hand wringing shares a non-negligible part of the blame for why hundreds of people are dead.

If Boeing had been allowed to say "of course our new engines are gonna pull the nose up a little harder, throttle back and climb slower if you don't like it" the MCAS system would never have been built to be the safety critical boondoggle it became. The plane itself handled just fine but the problem that they tried to solve with MCAS is that it wasn't identical to the prior 737. Even the most incompetent professional 737 pilot can fly a 737 that wants to <insert control input here> slightly when <insert other control input here> so long as they're expecting it (remember, they train for this stuff in simulator and most of these pilots are certified for multiple different aircraft) but just letting the pilots deal with it wasn't an option because the regulations disallowed that due in large part to decades of "people are just dumb cogs" type thinking.

And once the airplanes started falling out of the sky nobody could say "just turn of MCAS, it won't handle the same but close enough" because Boeing, the airlines and the FAA were all so balls deep in the lie they'd look like idiots if they changed their opinions and thanks to the society we've cultivated nobody is willing to be the first to break formation because that's who gets targeted by the bulk of the fallout.

> MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation. > The LEAP engine nacelles are larger and had to be mounted slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary ground clearance. This new location and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA. As the nacelle is ahead of the C of G, this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) "Stall characteristics". Several aerodynamic solutions were introduced such as revising the leading edge stall strip and modifying the leading edge vortilons but they were insufficient to pass regulation. MCAS was therefore introduced to give an automatic nose down stabilizer input during elevated AoA when flaps are up.

http://www.b737.org.uk/mcas.htm#background

[0]: https://www.airbus.com/en/products-services/commercial-aircr...

That summarizes why the plane did not go through a new type certification process - avoid costs of pilot training. Boeing instead painted over the differences (larger fans mounted forward) with software to make it feel the same.

The 737 Max was sold on not having to do certain kinds of retraining. "Something wrong with the training" is a divide by zero error here. There was no training. If memory serves this was also tied up in how much and what kind of recertification the FAA would require for a 'new' plane versus a refit of an existing one. Training means newness, and newness means retesting. The lies snowballed into dead passengers.

This seems a bit of a non sequitur from your first comment, but you did reply (here). I'm still not sure what your point is, though. What "narrative" are you referring to?

That's not the only problem with TFA. I worked on the Hercules, not any of the Boeing airliners, but this "30-year pilot" has some pretty fundamental misunderstandings of how MCAS works, what the effects of moving the engines are, and what actually went wrong with the 737 Max. Color me surprised.

Regurgitating the same "MCAS prevents the aircraft from stalling because it's unstable" shlock betrays the author's surface level (at best) understanding of the issue.

No, it's not unstable. The 737 Max exhibits stable pitch behavior along the entire envelope. A lot of people think "unstable" means "it crashes" but these terms have precise meanings.

The 737 Max is a stable airplane. One of the problems it exhibits is that with increasing angle of attack, the stick force does not increase (linearly is the requirement, I think, I'm writing from memory here).

The way you know this is because MCAS moves the horizontal stabilizer directly, and not the control column that the pilot is holding. An anti-stall device like a stick pusher or a stick shaker provides tactile feedback to the pilot via the control column. Moving the horizontal stab directly is (basically) altering the trim of the aircraft. Thus it is a handling-qualities system.

This is part of why the MCAS could not be decoupled from the flight computer as I recall. If you turned off MCAS, you'd be non-compliant in the wind-up turn flight regime, and when coming in on final if I recall correctly.

So in aerodynamic parlance it is stable, but with disqualifying flying characteristics that had to be mitigated via a gadget whose nature, failure modes, and existence was largely hidden from the pilot, and downplayed in the FMEA/FMECA. (Failure Mode, Effects, and Criticality Analysis)

This downplaying was specifically intended to keep regulators from stipulating enhanced training for pilots. Thereby saving money.

It's not just a cost saving measure.

MCAS was a sound concept. It's implementation, however, was not sound at all.

As far as MCAS goes, in my opinion Airbus got it right already in the 80's in their A320 with their flight envelope protection.

Yes, it would likely have been safer if the 737 Max worked as expected by the pilots flying it.

That only works if retraining is not actually needed. Boeing's own test program gave adequate (but undisclosed, at the time) information for an independent observer to conclude that this was not the case here.

I've never understood why the fix wasn't implemented in the elevator feel computer. Except perhaps that it doesn't have AoA inputs and it's an old hydroelectrical system for which there may be a lack detailed knowledge.

It comes from Boeing's checklists: https://i.stack.imgur.com/cRG4J.jpg

It makes perfect sense, because continuous operation identifies a fault condition. Under normal conditions, automatic systems may intermittently move the stabilizer, but never continuously. It may be faulty when moving on its own, but if it moves continuously without input, it's definitely faulty. That's where the name cames from: runs away into physical stops.