Indeed. This was a part failing on an aircraft in flight. It landed without incident, and was likely never in any sort of danger. Losing electric trim is an annoyance but also trims safety margins by, as I understand it, making autopilot impossible. So, it's good that they returned.
If this had happened on a 767 or A320 we'd never have heard about it.
What is Speed Trim? Well imagine MCAS, but instead of moving the stabiliser near the edge of the flight envelope, it moves the stabiliser all the time (when the speed is below mach 0.68). And instead of being introduced with the 737 Max, it was introduced 35 years ago with the 737 classic.
At least it's mentioned in the manual.
The investigation (and what we learned form it) into Boeing also didn’t help with confidence levels.
After a few new iterations nobody talks about the battery anymore. I’m not so sure how Boeing can turn this around relatively quickly.
[0] - https://www.cnbc.com/2021/03/29/southwest-airlines-adds-100-...
Meta note, this relatively frequent aircraft incident gets a lot of votes here on HN, yet the Southwest's order falls off the crack. Objectivity is as scarce on HN as on any other media frequently criticized here.
Not being open about it will have the opposite effect.
So in theory, trimming might be more difficult on the MAX than previous 737 models, especially at higher speeds (where there's more force on the control surfaces that would need to be counteracted in the case of runaway trim).
Component failures follow a bathtub curve. Mid-life is the lowest failure rate.
That's not really correct. The engines being in a different position means the aircraft doesn't meet a very specific criterion of the FARs (positive stick force gradient). The 737 Max has the exact same relationship with trim as any other airliner.
>Am I right in saying other aircraft e.g. an A320 would handle this sort of failure without as much risk to the plane?
No. TFA explicitly states this issue was not related to MCAS. It's likely an analogous failure on an A320 or a 737NG would still have necessitated aborting the flight.
It's like a bug that will not go away in some software. You think you've fixed it and all seems well and you get a good nights sleep with the gleam of satisfaction in your eyes.
But the next day your manager says "That bug is still there".
You incredulously do not believe that bug report and go to replicate it yourself.
And surely, under some edge weird case scenario, it really happened.
You put the fix in and uneasily sleep the next night. You actually dreamed about the issue. And wake the morning with no reports.
Over the next weeks and months, its all good. No new reports. and your mind has turned to some new projects. Surely that bug has been squashed.
And then one day...
I feel their pain. It's not the same, because lives and reputations are at stake. It's so much worse.But I feel their pain.
Inherent instability aside, fact remains the general perception is that Boeing retrofitted engines too large for 50yr plane design necessitating structural modifications which compromised its flight worthiness. As a result, software had to be written to compensate for this, which unbelievably, relied on input from a single sensor--iow, single point of failure.
The lost of trust is further exacerbated by the fact that Boeing/FAA knew there was high probability of another crash after the first catastrophic incident but refused to ground the planes continuing to let them fly while issuing deceptive public statements regarding the planes safety.
Boeing's largest market is China, which justifiably, will not allow the 737 to fly within their territory.
https://www.google.com/search?q=Outsourced+Profits+%E2%80%93...
It's not so much MCAS, electric trim, this, or that.
The bigger issue is it's too complicated, has too many features, and the FAA can't adequately oversee testing and certification all the way down the engineering stack. Furthermore, because of pressures to save a buck, Boeing is willing to cut corners and sacrifice safety by slapping a plane together without properly engineering or testing it. Because of this behavior, it's difficult to know how many other problems are lurking around like in the 787.
I don't get it. It is common for other airliners to rely systematically on trimming? Do other airliners have similar 'correcting' systems as MCAS?
Trim is changed for each phase of flight. Electric trim is just a motor spinning the manual trim control.
Most airliners will be doing constant trim adjustment.
If you want a real change of pace check out Airbus’ control system. It does a lot more intervention than anything Boeing does. Depending on the state of the aircraft the control stick will respond to input in entirely different ways (3 ‘laws’ that contain no less than 5 submodes). Sometimes it will act as you would expect a stick to act, other times it will intentionally limit what the pilot is asking of the plane, sometimes it will average what the two pilots are asking. Confusion about how the system works has caused at least two crashes I can think of (AF447, QZ8501). It’s killed more people than the Max, but it was written off as pilot error since it was operating as designed in both cases. It just happens to be a design that will change the way the plane is controlled when things go wrong. A few of the modes do in fact include automatic trim adjustments.
Airliners are packed with systems that make them dull and predictable to fly, because things can break on a sunny day over Texas, but also at midnight in the rain over the Atlantic, and the last thing you want your pilots to care about when they're stressed out, disoriented and working through complicated checklists is whether this particular plane has a weird tendency to pitch up at these particular conditions.
https://www.easa.europa.eu/sites/default/files/dfu/B737_Max_...
From TFA:
>A component of the main electric trim system became inoperative. Our pilots ran the appropriate checklist, which included manually trimming the aircraft. They returned to MIA and landed uneventfully. The issue was not related to MCAS.
That statement is from the airline, not from Boeing, so I'm more inclined to trust it. Additionally, if the airline lies and it turns up on an airworthiness audit (air maintenance organizations are subject to regular audits) then the penalties are quite severe.
In any case, per the airline's statement it was an issue unrelated to MCAS. Aircraft break literally every day in a myriad of ways that are often invisible/imperceptible to people riding on that very aircraft. In this particular case it was some unspecified component of the electric trim system.
You can look up the Master Minimum Equipment List for the B737[0] and see for yourself just how granular the approved maintenance program gets for aircraft like this. Everything on the MMEL is essentially an item that can be broken and the aircraft can still take off legally. Note that this is a different (and more rigorous) standard than "can be broken and aircraft can take off/operate safely".
I don't know exactly what broke here but I suspect it is a part that has broken on 737s hundreds if not thousands of times in the past, with similar outcomes.
I merely dabble in software but to further your analogy: This situation is when you've been dreaming about that bug for weeks and you get the call from the boss thinking it has recurred but instead it turns out it was a similar-smelling failure caused by some intern's microservice not failing gracefully when confronted with a network outage that brought down the system anyways.
Bah, what a vile comment. He didn't contest that at all.
It's the engineers who will have to go through this exercise of fixing it, and he identified something most of us can probably relate to.
Is this supposed to mean anything? To me it reads like an airline managed to get a massive discount on inventory that a struggling aircraft manufacturer hasn't been able to move for about a year due to their repeated problems with safety and accountability, which led the whole world to drop their orders.
737 classics are simpler and reliable.
The NG's randomly have hidden structural weaknesses exposed during runway overruns and hard landings when the fuselage breaks up because of Ducommun and Boeing negligence.
The MAX is a steaming pile that may be a white elephant around Boeing's neck.
The 787 is notoriously-bad.
The 777 is pretty good.
Airbus has had much more automation for years. Are they dropping out of the sky? Maybe they manage their complexity better than Boeing, who hires underpaid engineers to work on things that they're really not qualified to do.
I imagine that is how those poor pilots felt as their instruments screamed conflicting information at them as they tore through the skies above the mid-atlantic.
This situation is 100% opposite of basic stall recovery, but I don't know how much that still works when you are panicking and no longer feel like you can trust your instruments or your plane
But it's really not every failure. There were 2 other failures on Boeing airliners yesterday alone and nobody posted the other two.
American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure (OP's article)
Southwest B737 at Denver on Mar 30th 2021, speedbrake arming issue
United B739 at Denver on Mar 30th 2021, flaps problem
Day before
Batik B739 at Semarang on Mar 28th 2021, hydraulic fault
Aeroflot B738 at Krasnodar on Mar 28th 2021, flaps problems
Day before that
ANA B773 over Pacific on Mar 28th 2021, engine shut down in flight
iAero B734 near Evansville on Mar 27th 2021, loss of cabin pressure
Here's a 737-800 with a similar electrical trim issue recently https://www.youtube.com/watch?v=nLonztIXXWQ You probably didn't hear about that one
Like others said these aircraft fail every single day. People who read about them don't post them on HN because they're so common.
The odds of none of them having issues on a given day is slim.
The problem is that some failures mean the plan can't fly again until the part is replaced, and sometimes it's cheaper to turn around than to have the plan sit idle until they can get the replacement part out to it along with someone certified to repair it.
> This girl is one of a few 757s that Delta uses exclusively for charters. Lower cycles on them. 31.5 years old and still chopping up birds. Love it. Long live the 757!!
My point is that aircraft break all the time. Once in a while they break in such a way that they need to return to base. This wasn't an MCAS failure.
And for what it's worth I've pondered that before and my only conclusion was as others have said here, probably a lack of detailed organisational knowledge on the design of the pitch feel computer. Perhaps there are confounding factors, it has its own pitot tube but not a AoA vane for example. Or perhaps changing it may have triggered more regulatory oversight than MCAS did (unfortunate given events which followed).
That's likely why they didn't. That type of change is hard to conceal and far more difficult to keep out of the documentation. A software change could potentially be handwaved. Full on revamping of said system would probably have edged a regulator enough to have raised an objection or a deeper dive into the nature of the reconfiguration.
This to me seems a much greater process failure.
It was a really tragic accident with many lessons for anyone involved in the design of critical systems.
Deaths from car accidents per 100 million miles driven: 1.33
Deaths from plane accidents per 100 million miles by plane: 0.0077
(Note above statistics are from the US)
In your example, California to New York would be approx 3k miles while point Reyes is approx 150-300 miles depending on where you start. A 10-20x longer journey via plane is still an order of magnitude safer.
Per mile, the car is about 200x more dangerous - in fact the usual statistic is that getting on a plane is safer than driving to the airport, not doing the whole distance in the car.
People who fly in planes are generally not flying from every conceivable location on the globe to every other one in an even distribution and randomly using every type of plane available on every carrier. Neither are those driving cars driving from every possible destination to every other in every kind of vehicle etc.
Compare someone exclusively flying back and forth between one wealthy first world country to another on a Dreamliner run vs someone driving an 80's Ford Pinto regularly across treacherous mountain passes in the Andes.
Or the converse (use your imagination).
An important and useful statistic is that one particular, new model of aircraft is tremendously crashy considering the amount of time it's been in service.
It makes sense to avoid travelling on that aircraft, until it can be proven to have a flight-miles/crash ratio more in line with other models. (Which may take a number of years, or decades, especially if people are avoiding it...)
> Don't know if deaths includes pedestrian or bikes killed by cars, could be irrelevant if you only compare your odds to be alive after journey.
I agree this could be debated, but I don't think it's too useful to say "The journey was safer because rather than kill the person travelling it only killed a random pedestrian".
The problem was software designed to alter the flight profile automatically to minimize the differences and new training required (and was allowed to override manual inputs). Any pilot with full training of this specific plane without MCAS would have no problem flying it.
The planes didn't crash because they pitched up but because bad software mistakenly, and forcibly, pitched them down.
A quick google on "thrust line pitch moment" gave me this: https://www.homebuiltairplanes.com/forums/threads/thrust-ang...
" I want to adjust the thrust angle from where it was (0° with respect to the chord line) to reduce the downward pitching moment when thrust is added (or more importantly the upward pitch moment when thrust is reduced)"The forward position of the engines was done so that they wouldn't have to re-engineer half the plane to fit the larger engines. High bypass turbo fans are big, and they couldn't maintain ground clearance without either moving the engines up higher or making the landing gear longer. To move the engines higher they had to move them forward. So they did.
The new behavior of the aircraft required retraining and making sure pilots knew how the throttle and pitch were related. Mind you, a lot of aircraft have such relationships, so this is not in itself a flaw.
The real flaw came when they decided to replace training with software, and then conveniently forgot to tell anybody about the robo-pilot that they put in the cockpit. THAT was the failure. The airplane itself, even without MCAS at all, would be a bit more of a handful to fly, but nothing terrible. With a properly functioning MCAS, and proper training about how to disable it in case of a problem, the issue is solved. And that's what the FAA believed happened when they recertified the 737 MAX to fly again. But by now the reputation has been tarnished so badly that we're hearing news about unrelated failures because it happened on a 737 MAX.
So you can see the real failure isn't aerodynamic, its pretty much everything else.
If I got any details wrong, I apologize. I'm flying by the seat of my pants on this layman's analysis after a long day.
Any conventional airliner has this "flaw". If you are at low airspeed and you push the throttles forward, an A320 will exhibit nose-up pitch, too. It's a direct consequence of having giant engines slung kinda-sorta-underneath the wings of a low-wing monoplane.
The problem is that at high angles of attack, the nacelles start to produce lift, and with the more forward position, they cause a greater pitch up force than previous versions.
https://transportation.house.gov/imo/media/doc/2020.09.15%20...
And this, I think, is where the whole faulty/flawed thing gets introduced :
> Faulty Design and Performance Assumptions.
> Boeing made fundamentally faulty assumptions about critical technologies on the 737 MAX, most notably with MCAS. Based on these faulty assumptions, Boeing permitted MCAS—software designed to automatically[...] It also expected that pilots, who were largely unaware that the system existed, would be able to mitigate any potential malfunction. Boeing also failed to classify MCAS as a safety-critical system, which would have attracted greater FAA scrutiny during the certification process.[...]
So, I would agree that Boeing's design flaw here was not alerting the pilot with a huge red warning light (and being cheeky about re-certification). But I don't think that this report goes so far as to say that the airframe was flawed and therefore necessitated MCAS.
Stalls are not a serious problem, they're basically the first thing pilots learn to solve. And there are plenty of aircraft that are more challenging to fly. That's what training is for.
The real issue is that pilots should have full understanding of the behaviors of the airframe instead of relying on software to change it. Especially when they don't have full understanding of the software either, and the system can both override manual inputs while being susceptible to faulty sensors.
They account for 25% of fatal accidents [1]
[1] https://www.aopa.org/-/media/Files/AOPA/Home/Pilot-Resources...
So to add context, stalls under commercial part 135 flights are extremely rare and even less fatal. There's almost always some other compounding issue that led to the stall instead of just basic flight maneuvering.