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Similarities Between the Lion Air and Ethiopian 737 Max Crashes (thepointsguy.com)
263 points by jaredwiener 9 days ago | hide | past | web | favorite | 208 comments

Sympathies for all the victims and their families, incredibly sad.

Many of us have heard the phrase "If it ain't Boeing, I ain't going." In reference to Boeing's perceived safe planes. This phrase has lost any meaning to me, and in fact, I'm feeling the opposite way right now.

Boeing's response to the first 737-Max Lion Air crash was abhorrent, in my opinion. While they were taking the time to blame the Lion Air pilots reaction to the plane's issue, and stating how safe the 737-max was, they were also working on urgent patches to their software. The patch is still not yet deployed, but the planes continue to fly.

If initial info of this crash points to a related cause to the Lion Air crash, anything less than a full grounding of all 737-Max aircraft seems incredibly dangerous. I get the feeling that Boeing executives have checked their better moral judgement at the door and are thinking solely in terms of dollars.

I can't help but feel that Boeing and US regulators would have taken the issue identified after Lion Air much more seriously and been much more likely to take action and responsibility if it was a US flight. That thought leaves me with incredibly sour taste in my stomach.

For those who may come to Boeing's defense, take a look at how pilots of the 737 Max responded to the Lion air crash - often with anger.

[1] https://www.nytimes.com/2019/02/03/world/asia/lion-air-plane...

[2] https://www.washingtonpost.com/business/2018/11/13/pilots-un...

[3] https://www.fullwsj.com/articles/regulators-push-for-clarity...

[4] https://www.fullwsj.com/articles/boeing-and-regulators-delay...

We can't afford to wait for evidence proving beyond a reasonable doubt that this aircraft is dangerous.

Probable cause should be a sufficient standard.

Two crashes in similar circumstances is probable cause to take them all out of service until they figure out what the hell is going on.

For myself and my family, we won't wait for regulators and airlines to act. We will not fly the 737 Max.

It's interesting that you reach that conclusion.

I'll fly 737 max.

I won't fly Lion Air or Ethiopian Airlines.

Southwest: fleet size 754, founded 1967, total of seven accidents with 3 deaths.

Ethiopian Airlines: fleet size 107, 64 accidents with 459 deaths since 1965.

I don't have data on flight miles or flight segments by type of aircraft, so let's do a quick and dirty estimate.

Let's say there are 40,000 commercial aircraft worldwide and 350 of these are the Boeing 737 Max [0].

If all aircraft are equally likely to crash, then the probability of a given crash being a 737 Max is 350/40000 = 0.00875.

The probability that two crashes are both 737 Max is 0.00875 * 0.00875 = 0.0000766

It's extremely unlikely that an aircraft representing less than 1% of the global fleet would crash twice in a short period of time unless there is a serious defect with that aircraft.

That's well past probable cause at this point. This aircraft should be grounded until they figure this out.

[0] https://en.wikipedia.org/wiki/List_of_Boeing_737_MAX_orders_...

> The probability that two crashes are both 737 Max is 0.00875 * 0.00875 = 0.0000766

You need to multiply this by every combination of two crashes in the observed time period with starting and endpoints not cherry picked to include 737 max crashes though.

Be my guest. You'll find that the probability of a rare aircraft crashing twice in a short period of time is infinitesimal, unless that aircraft contributed to the catastrophe.

It's hardly infinitesmal, that's my point.

With an average of 175 737's operating since launch, 4K total widebody commercial aircraft and over a dozen widebody crashes in that period, you get over 10%. Some estimates there but you still have the endpoint issue as well.

There have been a total of 5 commercial air disasters in 2018 and 2019 with fatalities that didn't involve hijacking, landing short of the runway or overshooting the runway [0].

And that includes the crash of a cargo flight with no passengers where the crew was killed.

The 737 Max 8 was involved in 2 of those 5 disasters.

There are between 25,000 and 39,000 commercial aircraft in service depending on who you ask [1].

With 350 737 Maxes delivered so far, that's at most 1.4% of the total today, probably less than half that this time last year. Let's call it 1% on average for 2018 and 2019 combined.

There are 10 ways you can have 2 Max crashes out of 5 total crashes. So the probability is 10 * 0.01^2 * 0.99^2 = 0.00098

Even accounting for n choose k and longer endpoints, it's still an infinitesimal probability that we'd see two catastrophes with the same rare aircraft -- unless that aircraft contributed to the catastrophe.

It should be grounded.

[0] https://en.wikipedia.org/wiki/List_of_accidents_and_incident...

[1] https://www.telegraph.co.uk/travel/travel-truths/how-many-pl...

It is possible for both a carrier to be more at-risk for crashes as well as a plane to be more at-risk for crashes.

The FAA issued an emergency operation directive for the 737 Max due to inaccurate sensors which could lead to a crash. I'm not entirely sure why you're ignoring that fact and deflecting to something unrelated.

> deflecting to something unrelated

I don't think it is unrelated that the only accident thus far of a plane with a failure mode that is more difficult for pilots to respond to was on an airline with a notoriously bad safety record.

I fully recognize the fact that airlines and pilots were not informed well enough about MCAS, but I'm also not ignoring the other circumstances of lion air 610

Safety in depth - a single failure should not be a problem. 610 crashed as a result of MCAS, but also a number of other operational failures of Lion Air and the pilots.

rconti 8 days ago [flagged]

Downvoted. Your data is terrible and should be cited. The 737Max has only been flying for 2-3 years. Southwest is irrelevant (I say as I sit on a SWA flight on the tarmac in SAN waiting for a replacement crew member). I made damn sure it wasn’t a Max (which I flew on Aeromexico twice back in September).

I have no idea where your Ethiopian stats come from because I’ve heard nothing but great things about them. Feel free to rebut.

“Or how about Ethiopian Airlines? Here is another impoverished country surrounded by rugged terrain. Yet the record of its national carrier — three fatal events, one of them a hijacking, in over seventy years of operation — is exceptional. Ethiopian is one of the proudest and arguably one of the safest airlines in the world.”


Unable to delete, as I was able to find stats last night that confirm Parent's Ethiopian Air stats, and I regret the tone.

Regardless, Ethiopian Air is considered a top tier safe carrier.

I think accidents per trip (flight leg) is a more useful metric than accidents per year. If you're interested in mechanical issues then you'd also need to remove terrorism related deaths.

Yes, it's a small sample size, but if you look at the fatal accident rate per flight leg of a 737 MAX 8, I'm sure it's much higher rate than any other modern aircraft.

According to https://www.tripsavvy.com/the-safest-aircraft-54428, the following modern aircraft have fatality-free records:

Boeing 717 (formerly the MD95)

Bombardier CRJ700/900/1000 regional jet family

Airbus A380

Boeing 787

Boeing 747-8

Airbus A350

Airbus A340

This list is meaningless without accounting for the number of aircraft & the number of miles they have flown. For example, the 737 is not only the world's most popular commercial airliner, it's simultaneously the "most dangerous plane" because it has had 145 accidents [1] and one of the safest planes because the 737 NG variant has only had one crash in 16,047,900 flight hours. [2]

[1] https://www.airfleets.net/crash/stat_plane.htm

[2] http://www.travelvivi.com/the-safest-aircrafts-in-the-world/

And indeed, the 787, 747-8, A350 and arguably the A380 are all new planes that have not accumulated the decades of flight history with huge fleets that the 737 has.

True, but the 737 MAX 8's first commercial flight was in 2017, much newer than any of the aircraft on the above list. The point is that such a new aircraft already has a far worse safety record than plenty of aircraft that have been around for years. I think it's irrelevant to compare 737 subtypes, since discussion focuses on the 737 MAX 8 variant specifically.

> And indeed, the 787, 747-8, A350 and arguably the A380 are all new planes that have not accumulated the decades of flight history with huge fleets that the 737 has.

The 787's first commercial flight was in 2011. The 747-8 in 2012. A350: 2015. A380: 2007. All predate the 737 MAX 8 by years, and have better safety records.

You have to know that the problematic Anti-Stall feature was just recently added in the MAX rev 8. The older rev 1-7 don't have it. It might have other stall problems due to being backheavy, but the traditional stall warning should have been good enough. There was no accident in rev 1-7, none with the improved Southwest configuration (with two sensors) and already two complete losses with the updated MCAS rev 8. They already did two more updates on this (9 and 10), but still not safe enough for modern safety standards.

Sure, but for comparison, the original 737 was launched in 1967 (!) and even the 737 NG has been flying since 1997.

So while having two MAXes crash after takeoff mere months apart is indeed statistically unlikely, I wouldn't necessarily leap to the conclusion that the two accidents are related just yet.

The Concorde used to be #1 on this list, while being the least safe commercial jetliner of all time.

Southwest also took steps to add additional AoA sensor information displays to their 737 Max aircraft in the wake of the Lion Air crash. The operator does make a difference.


If Boeing is issuing software updates that disable manual override without telling pilots, Boeing is completely at fault here, and some of the engineers/executives should face criminal charges.

I am confused. When I read the article about the Lion Air crash, I thought one cause of the crash was that the pilots hadn't been properly trained in the manual override procedure that can deal with the problem with malfunctioning sensors.

I don't understand how a software update can override a completely manual override.

The procedure that pilots are taught to override auto trim was unchanged, but I think that previous auto trim systems could also be "out muscled" just by pulling back on the yoke without actually switching on the manual override. It's that second part that people are pointing out (though I will in turn point out that the pilots on the flight prior to 610 faced similar issued and used the manual override to respond to them).

> criminal charges

Boeing informed the FAA of the changes, and the FAA decided that the pilots and airlines did not need to be informed. Criminal charges for Boeing would be extremely surprising.

Would the FAA decision have any bearing on what happens in Ethiopian airspace?

Taking your question at face-value: FAA guidelines apply to all airlines that fly into the US - Ethiopian does.

Good point. Boeing should be have told every customer that bought a plane.

But Southwest did something nobody else did. They added a second AOA sensor. This should mandatory by every security standard and Southwest did good by mandating it, but Boeing still got away with all other companies.

Good luck flying Southwest in Africa.

You write as if you always have a choice which airline to use. Southwest is mainly USA domestic with a few vacation destinations nearby USA.

It will take mere days to determine definitively if the crashes involved the same trim system.

I think you are completely free to avoid the 737 MAX as long as you like, but it seems like panic and hysteria to call for a widespread public reaction before any actual crash data is available.

Quite the opposite. In lie of facts one should err on the side of caution. So far the similarities to the previous accident are striking. The whole fleet should be grounded immediately.

If you fly an airline with MAX 8's in fleet, you can show up at the gate and find out it's a MAX 8 when it wasn't previously scheduled, and it will not be free for you to avoid that flight.

It doesn’t make sense to me how they can continue blaming pilots if the cause of today’s crash is the same as last year’s. Even if they tell us with undisputable evidence that the plane was operating within standard operating procedure, it sounds like that SOP is unintuitive garbage and putting everyone at risk. The latter part is what matters the most. I don’t see any sane or reasonable path other than grounding the 737 Max.

I have no expertise in the area, but I doubt it's the same cause. Every 737 Max pilot will certainly be aware of the Lion Air crash and the ways to mitigate that particular behavior of the aircraft.

We need to wait for the investigation before we jump to conclusions.

Not necessarily.

The 737 Max is the same type rating as all other 737. That means the pilots and crew switch back and forth between the Max and non-Max planes — despite the fact that they act very different in certain circumstances.

This was intentional, it saves airlines money to have fewer type ratings.

Besides, so soon after take off there’s very little time to recover when your plane is overriding you attempts to keep it from nose diving into the ground. It’s not as simple as flipping a single switch.

> It’s not as simple as flipping a single switch.

Except that's exactly what it is and then manually setting the trim. The NY times had an excellent article about the procedure:

> The crucial step, would be to reach across to the central console to a pair of switches, and flip the switches off. Those switches disable electric control of the motor that moves the stabilizers up and down, preventing the anti-stall system from exerting control over their position.


If you're used to flying a plane for several thousand hours that's not going to be second nature at all (when the procedure has changed).

You really should watch this video just to get an idea of how catastrophic this error is:


Not sure what I'm meant to glean from that video? It's the last 10 seconds of the flight?

The lion air pilots had 15 mins to disable the automatic trim system and simply set the trim manually. It's turning off a switch and spinning a wheel. Manually setting trim is second nature to student pilots.

They should also have read the log prior to departure and seen the previous four flights had this problem that did exactly this. Quite sure pilot error will be the outcome for lion air.

There's absolutely no difference in procedure here a normal 737. Unsure where you got that idea from.

Perhaps how catastrophic this issue could be while the flight is still in low altitude during one of the busiest phases of operations?

The procedure to set the trim manually was the same, but I assume that in most flights the actual flywheel is never turned by hand (and thus rarely deactivated). I'm sure most pilots use the fly-by-wire systems or autopilot.

The procedure which was different was the automated MCAS system - pilots who have logged significant hours flying the previous model of 737 would be unprepared for this during an extremely busy phase of the flight.

Ultimately, yes, it was the pilots error when they didn't take the proper actions when the problem first occurred. Nevertheless, we must first take into account why the automated system failed to begin with, and why the pilots made the error (lack of training, sleep, preparation).

This isn't binary, and the fact Boeing is issuing a patch for the software systems as a direct result of Lion Air tells me there is more to the story than just "pilot error".

Sensors fail all the time modern aircraft, people would probably be quite scared knowing how often.

After the Airfrance airbus incident they also introduced a "patch" to protect the aircraft from erroneous pilot actions leading to stalls when indicators are incorrect, those fixes were certainly not indicative of guilt but just another layer to stop pilots making mistakes.

The lion air pilots had 15 mins to disable the automatic trim system and simply set the trim manually. It's turning off a switch and spinning a wheel. Manually setting trim is second nature to student pilots.

To put it bluntly only a fool is going to start flipping switches willy nilly. Boeing has a procedure out to handle runaway stabilizer trim, and that's to flip the switches, but the Lion Air pilots did not encounter a runaway stabilizer so why would they go down that checklist and potentially add to their troubles? In the case of the cutout switches, those switches do different things on the NG and MAX (and are thus labeled differently) which potentially adds to the confusion and reduces the incentive to experiment. You're talking about counteracting a system that Boeing hid from pilots — hardly pilot error.

In fact if you look at the FDR data you'll see that the pilots were able to temporarily disable MCAS with the trim buttons on the yoke. Every time MCAS trimmed down, the pilot trimmed up and was able to maintain appropriate trim. That worked, and it seemed like the plane was largely under control (until it wasn't).

Meanwhile the unreliable airspeed indicators were illuminated and one of the stick shakers was going off, and there was probably an EICAS message about the elevator feel system but no actual indication of the underlying problem with AoA was given because Boeing charges extra for that. So, with the assumption that you had the stabilizer trim under control, why would you add to the significant workload by disabling the electrical control of the stabilizer?

> with the assumption that you had the stabilizer trim under control, why would you add to the significant workload by disabling the electrical control of the stabilizer?

I'm struggling to see how you think having to make manual adjustments every 30 seconds is "under control". Check the flight profile, it was never under control.

> the Lion Air pilots did not encounter a runaway stabilizer

What did the pilots on the four previous flights encounter? Did they not follow procedure correctly by overriding it? The trim stabiliser had to be adjusted 23 times during the the fatal flight, this is a solid fact. After a few times it should have been very apparent that there was a problem related to the automatic trim system and switched to manual.

Manual trim would only get adjusted a only few times during a regular flight, it's a very basic skill and the trim wheel itself takes up a huge amount of real estate in modern cockpits.

Sorry but you've written a lot of terribly inaccurate stuff here. Let's see what the report says.

There are dozens of design flaws in modern aircraft, a miniscule amount are unrecoverable following procedure.

The process to manually override trim on a 737 that should have been followed:


I'm struggling to see how you think having to make manual adjustments every 30 seconds is "under control". Check the flight profile, it was never under control.

Every time MCAS trimmed down, the pilot trimmed up which resulted in two things: MCAS stopped trimming down, and the stabilizer was adjusted up. That's not a runaway situation.

What did the pilots on the four previous flights encounter?

The previous pilots ran into MCAS trimming the stabilizer down inappropriately. They wrote it up as a speed trim (STS) failure. The crew on the fatal flight read STS and was probably thinking STS when they crashed. Unlike the undocumented MCAS inputs, STS can be disabled by moving the control column.

Did they not follow procedure correctly by overriding it?

There was no procedure, MCAS was undocumented.

Manual trim would only get adjusted a only few times during a regular flight

You're almost never going to crank the trim wheels by hand but an NG pilot may be used to having to add input to counter STS.

The process to manually override trim on a 737 that should have been followed:

The pilots were presented with more than just uncommanded trim adjustments, they were presented with multiple, seemingly unrelated, failures. The failed AoA measurement meant they had no idea how fast they were going (new behavior on the MAX, see the repeated queries they made to the ATC), one of the stick shakers was going off (unsure if plane is going to stall and fall out of the sky), and there was probably a warning about the "elevator feel" system on EICAS like on the previous flight.

When faced only with uncommanded trim, sure, they probably would've thought STS because that's the only system Boeing bothered to document. In an ideal world the pilots would've recognized that this wasn't STS. In reality the pilots were busy triaging a variety of symptoms because Boeing did not make appropriate warning / status indications standard equipment on the MAX nor did Boeing actually document that MCAS exists (except in Brazil).

The only error that the Lion Air crew made was in not being clairvoyant.

Why arent pilots able to take full and absolute control of a plane at any time whatsoever?

What does "full and absolute control" mean in the context of a fly-by-wire aircraft? AA587 is blamed on a pilot's inputs driving a structural capability exceedance in the vertical stabilizer. For reasons such as these, all fly-by-wire aircraft will have some measure of envelope protection whereby pilot inputs projected to exceed aircraft capability will be limited. There is always "interpretation" of pilot inputs involved in fly-by-wire systems. The key is in making available all control power to the pilot that will not result in catastrophic structural failure of the aircraft. And the associated challenges are knowing exactly where those boundaries should be set in the design of the control system, as well as the knowledge of the aircraft state to the flight computers.

Thank you for the extensive response. With that context, I would say "full control" should amount to the ability of a pilot to overrule systems that may send an aircraft nosediving due to faulty sensors.

Did the pilots of the Lion Air flight and possibly the Ethiopian Air flight understand what was wrong in-flight and were unable to fix it due to an inability to override aircraft controls?

This is what I am getting out of the discussion so far but maybe I am gravely misunderstanding what's happening? So as a passenger without any knowledge of aviation systems my question is merely whether the pilot gets control over the aircraft when he demands it? Fly-by-wire should at least never lead to autopilot suicide, even if it has to ensure flight integrity to a certain degree due to the technical nature of large, modern aircraft.

> Thank you for the extensive response. With that context, I would say "full control" should amount to the ability of a pilot to overrule systems that may send an aircraft nosediving due to faulty sensors.

Thanks for reading it :) . As you phrased it specifically, I can't disagree with you. But in these systems, the devil is in the details. For Boeing's MCAS, which is like an add-on piece of functionality to the core control system, it seems like an obvious piece which should have a manual override - and it does. The criticism, as I understand it based on Lion Air, is that the override functionality is not obvious and if you were previously a 737 pilot on non-Max variants, you might not know about this or have practiced its use.

However, consider safety systems such as Automatic Ground Collision Avoidance System ("Auto GCAS") or Automatic Air Collision Avoidance System ("Auto ACAS"). These systems are designed as reactions to multiple known cases of human error that have resulted in otherwise under-control aircraft being flown into the ground or other aircraft. They are specifically designed to override a mistaken human. Technically, it's not impossible that pathological failures or spoofing could trigger these automated systems, which would wrest control away from pilots. Should such systems be overridable at all times?

Resolving these kinds of issues does involve some judgment and adopting a philosophy prior to the implementation. Airbus and Boeing, for example, have historically differed in their philosophies, each with reasonable rationale.

I personally favor the approach Boeing has historically used, with AF447 and QF32 illustrating some of the pitfalls of Airbus' approach. For example, as pointed out by ggreer in https://news.ycombinator.com/item?id=19355402 , being susceptible to common mode faults.

However, I still fly on either manufacturer's aircraft without hesitation.

We demand this level of conscious awareness and control of 4-5 year old children in our society but machines that carry dozens of lives are not held to such a standard of attention and interaction. This might be something that AI can address, but most current offerings still lack features we consider essential for even very young children.

That's like suggesting that once a patch exists for a vulnerability in software that tye vulnerability no longer exists.

Dissemination of information about a risk is an entirely separate issue from creating a solution to the underlying flaw.

Nope. We ground the planes until we figure out what’s wrong. There is simply too much risk in “not jumping to conclusions,” unless you wouldn’t mind the deaths of a couple hundred people on your head?

>Every 737 Max pilot will certainly be aware of the Lion Air crash and the ways to mitigate that particular behavior of the aircraft.

I think that is a good point.

My guess is that it's related to Indonesia's poor historical air safety record. This goes for ferries, buses and trains as well. Penalties for not ensuring safety are far too lax hence this cycle continues.

But I understand in this case we are talking about a brand new aircraft.

Sounds like 737-Max has an inherent design flaw that they tried to patch with a software fix adding unnecessary complexity, a single point of failure(AoA sensors) and more importantly adds an element of surprise for the pilots:


Basically pretty shitty system design.

> Many of us have heard the phrase "If it ain't Boeing, I ain't going."

Do people out there really think Airbus have such lower safety standards that they won't fly on them? They must struggle to get around even the US domestic routes these days.

And not just Airbus. Hard to imagine how you're going to do much regional travel and avoid Embraer, Bombardier, or ATR.

Isn't this a reference to airplanes like MD DC-10? Airbus is a super new company.

> Airbus is a super new company.

Not really sure what you're on about - Airbus' passenger jets started only a decade after McDonnell Douglas and Boeing's. A300 flew around 1970. DC-8 flew around 1960, same as the Boeing 707.

Th grandfathers of some people on this site would have been flying on Airbus.

> The grandfathers of some people on this site would have been flying on Airbus.

I like the image, but I think you can make it much stronger. The grandfathers of many users of this site are still flying on Airbus (as well as all other current planes), so I think you being at least a couple generations to conservative. Instead, I think it's safe to say that the "great-great-grandfathers" of some of the users of this site almost certainly flew on an Airbus.

For ease of math, assume an 18 year-old-user born in 2000, 25 years per generation, and a 75 year lifespan. Their father was born in 1975, their grandfather in 1950, their great-grandfather in 1925, and their great-great-grandfather in 1900. That great-great-grandfather died in 1975, and thus assuming they flew in the last years of their life, would likely have flown on an A300.

Given that these assumptions might be closer to average rather than extreme, I don't think it would be unreasonable to bet that at least one user's great-great-great-grandfather flew on an Airbus as well.

You are right, Airbus is not as new as I thought. Still I think it was a reference to DC-10?

> If it ain't Boeing, I ain't going

No one actually says that. Even Boeing itself, when arranging corporate travel for employees, picks whatever flight is available with reasonable airfare regardless of aircraft type.

It’s a common saying in the northwest. If not actually obeyed.

Yup Boeing has lost its way and is another typical bureaucratic hell hole of a company like IBM. I’ve heard horror stories about the 787 development process as well.

There was a quip back in 1997 that "McDonnell Douglas bought Boeing with Boeing's money" referring to the restacking of the Boeing management with ex-McDD executives after the merger.

The last true engineering-led Boeing was the 777. Chaotic mess of 787 development or apparent stretch-too-far Max are pure McDD.

I completely agree and I was utterly shocked when so many “self-professed experts” on HN just dismissed everything to accuse the pilots that didn’t read the manual. As I said before I will not fly on a 737 max until all this shitshow is cleared, and I urge everyone else to avoid it.

I checked my next flights, some Airbus, a Fokker and two 737-800. Luckily not the MAX. I never checked the aircraft model before booking but I'll start doing it. I won't fly a MAX.

The airplane can be changed at the last minute, but it's worth a try I guess.

Better to be safe than to be sorry, especially when your life is at stake.

I flew the 737 Max about a month after the Lion crash. I sure as hell will not be getting on it anytime soon.

I’m curious why they would need that system in the first place. Pilots know to trim for level flight so the computer doing it automatically seems unneeded regardless of new engine placement.

The engines are more powerful and further ahead of the wing on the MAX. This means that the plane may pitch up significantly (and potentially stall) if you apply a bunch of thrust. MCAS was designed to prevent this.

There was, IIRC, a similar incident in an 737 Classic (go around in England that achieved a dramatic nose up pitch IIRC — not the Tailwind incident) but I can't seem to find the entry on avhearld.

You're probably referring to this one - Thomson 737-300 at Bournemouth in 2007. Scary reading the full report: 44 degrees nose-up and 82 knots indicated air speed!


Yep, that's the one. If memory serves, most or all planes with the engines under the wing will pitch up when you apply thrust. Most planes will have an effective enough elevator to counteract this... but it seems like the 737 does not.

The new system (MCAS) was not intended to take action in normal flight. It was intended the trim in certain scenarios (roughly high AoA + steep turn + high g + near stall), but on lion air 610 the AoA sensor was malfunctioning, which caused MCAS to activate when it shouldn't have.

"if it was a US flight."

Or Airbus.

> If it ain't Boeing, I ain't going

I have mostly had the reverse sentiment; my experience is mainly based on 777-xxx planes, but I find the experience in those so horrible that I try to avoid Boeing in favor of Airbus. Every time when I cannot (like last week when I flew with a 777-300er) I get reminded how crap these things really are. Not talking safety but general feel and comfort; basically everything is worse; noise, seating, effects of turbulence etc. And I have noticed this across multiple premium airlines.

I also wonder if the fact that Boeing is a US company has anything to do with it. If this was an Airbus would the US have required grounding of the planes? I believe your point about if it happened in the US they would still have been grounded but perhaps if it wasn't a US company they would have pushed for grounding to be safe even if it did not occur in the US.

US never grounded Airbus, but grounded all Boeing 787s once.

Lion Air wasn't maintaining their aircraft well. The new anti-stall feature that seemed to cause the Lion Air crash shouldn't have activated under a sensor fault scenario, yes, but software alone isn't to blame for that one.

The Lion Air crash was a 2 months old plane. I'd expect a 2 months old plane to be air worthy even if some maintenance was neglected.

But they neglected maintenance when serious issues with the plane were apparent. The pilots of the flights prior to 610 noted that the two AoA sensor readings differed by ~20 degrees, and nearly aborted their flight before overriding the auto trim.

Flight 610 should never have taken off.

That's a misstatement of what occurred. The aircraft had a fault on the previous two flights and was repaired before the fatal flight.

> Flight 610 should never have taken off.

A repaired aircraft should not take off?

The preliminary report from the investigation of LNI610 disagrees with you: https://reports.aviation-safety.net/2018/20181029-0_B38M_PK-...

The AoA attack sensor was replaced prior to flight LNI043 (he flight prior to 610), in which the pilots declared pan-pan and had to manually override the auto trim systems (which include MCAS). Between 043 and 610, there was further maintenance that included flushing the pilot valves and cleaning electrical connectors, but the AoA sensor was not replaced between 043 and 610.

An aircraft that was repaired followed by one flight in which the pilots declared abnormal operation and performed 3 non-normal checklists should probably not fly again until they figured out what happened, and the next flight should definitely be aware of the incident on the flight prior. 043 faced and overcame the exact same malfunction as 610 - to me that indicates a clear failure. If you keep flying an aircraft that malfunctions on each flight, you're pressing your luck.

> Between 043 and 610, there was further maintenance that included flushing the pilot valves and cleaning electrical connectors, but the AoA sensor was not replaced between 043 and 610.

They followed Boeing's procedure in attempting to address the issue again (after already replacing the sensor). That's a completely appropriate action.

> the next flight should definitely be aware of the incident on the flight prior.

It is in the log book. Is this a reference to something particular?

> 043 faced and overcame the exact same malfunction as 610 - to me that indicates a clear failure.

I agree, that's why maintenance conducted a repair.

> If you keep flying an aircraft that malfunctions on each flight, you're pressing your luck.

They attempted two repairs in accordance to the manufacturer's procedures within that time in order to resolve the malfunctions.

This post references the report and you clearly read it enough to know your original conclusion was mistaken, but are still arguing you're right by trying to shift the discussion. You've gone from "they flew a broken aircraft" to "alight, so they repaired it twice, but you cannot ever trust a malfunctioning aircraft again." By that logic every single commercial aircraft would be in the junkyard... Repairing malfunctioning systems is normal, attempting two different repairs isn't uncommon either.

It's not fixed until it is fixed.

I understand that with physical systems, the cost and complexity of detecting is higher, but if you're putting other people on the line, you damn well better do a live test of your vehicle before another living soul not certified as a pilot or flight engineer is allowed on board.

The more I read about this, the more it appears to me that excessive trust is placed on filed paperwork. Nothing says a fix is done like a successful test flight that specifically attempts to recreate the conditions surrounding the original failure.

I don't disagree, but now we're holding Lion Air to a much higher standard than any other commercial airline, including US and EU based ones.

Certain repairs are tested. Non-safety critical sensors like AOA are not, because you're meant to be able to land if there's a malfunction. Obviously not in this case, which points to procedural problems beyond any one airline.

The AoA sensor stopped being non-safety critical when it's output was allowed to drive a system capable of endangering the aircraft.

I don't believe Lion Air is directly responsible; they didn't test flight it, but they didn't know they should either due to Boeing's poor communication of the functionality and justification for MCAS.

It's a grievous failure all around, and yet another reason I stand by the belief that if there is doubt, there is no doubt.

> You've gone from "they flew a broken aircraft" to "alight, so they repaired it twice, but you cannot ever trust a malfunctioning aircraft again."

If you think I've changed my argument, you misunderstood my comments. I still think that they flew a broken aircraft.

I'll stand by my statement that 610 should never have taken off, and I'm somewhat surprised that it is contentious. I don't care if all the protocols were followed and the logs made (though obviously the pilots of 610 didn't understand what the previous pilots had done to respond to their incident) - in retrospect, we know that the aircraft was not airworthy going into flight 610, so something needs to change so that next time that is detected before takeoff. Whether that is better observation of the protocols or better protocols, I'm not sure.

Does repaired in this context also include a successful in-flight test?

At some point, the complexity of system integrations requires that you do something more than bare minimum component retesting.

The bathtub curve suggests you shouldn’t. A five year old plane should be safer than a two month old one.

Particularly on a new design variant, there are probably a lot of design/manufacturing issues that can only be found when operated in the field.

Apparently you haven't maintained an airliner.

I think there’s just fatigue with Indonesian airlines’ spaced out attention and not caring about safety over the years, of course the time it’s due to a different reason then no one believes it. It’s the natural consequence of their past record and ignoring warnings.

If there’s a recent case of an airline with a solid track record of following safety recommendations and Boeing not responding appropriately to a crash then that would be different.

AFP is reporting that an eyewitness saw the aircraft on fire before the crash. If confirmed, that makes this quite difference circumstances to the Lion Air crash.

> An eyewitness told AFP the plane came down in flames. “The plane was already on fire when it crashed to the ground. The crash caused a big explosion,” Tegegn Dechasa recounted at the site. “I was near the river near the crash site. Shortly after the crash police and a fire crew from a nearby air force camp came and extinguished the plane’s flames on the ground.”

> He added: “The plane was in flames in its rear side shortly before the crash. The plane was swerving erratically before the crash.”

Source: https://www.theguardian.com/world/2019/mar/10/ethiopian-airl...

With all respect to the witnesses, early eyewitness reports are notoriously unreliable. I remember reading the exact same thing about the plane that crashed in NYC shortly after 9/11. There were also many ‘eyewitnesses’ claiming to see the crash of the Malaysian airliner. This report may wind up to be substantiated, but I wouldn’t put any weight on it until then.

See also the multiple eyewitness accounts of what brought down TWA-800, many involving a surface-to-air missile. The most likely explanation supported by evidence turned out to be faulty wiring igniting fuel vapor in the center tank. However, it took years of investigation and evidence gathering to finally put that initial speculation to rest.


Also TWA 800, where many eyewitnesses saw a missile that was never there.

not sure if citing that as an example is such a good idea, considering everything surrounding it. You do have to reject an awful lot of evidence to claim with certainty there was never a missile.

They spent 4 years and $40M on the investigation which including recovering most of the fuselage from the Atlantic and reassembling it in a warehouse.

Take these testimonies with a bit of salt. The standard item in my repertoire on this is AA flight 587.

“ According to the National Transportation Safety Board, which announced this month that it had gathered 349 eyewitness accounts through interviews or written statements, 52 percent said they saw a fire while the plane was in the air. The largest number (22 percent) said the fire was in the fuselage, but a majority cited other locations, including the left engine, the right engine, the left wing, the right wing or an unspecified engine or wing. Nearly one of five witnesses said they saw the plane make a right turn; an equal number said it was a left turn. Nearly 60 percent said they saw something fall off the plane; of these, 13 percent said it was a wing. (In fact, it was the vertical portion of the tail.)”


And we rely on eyewitnesses to send people to jail for life.

Or kill them, depending on state.

It could be possible that turbines have stalled as a result of vigorous AOE changes and "flamed out"

A distortion-induced flameout is pretty unlikely - though something like a compressor stall is not out of the realm of possibility. These can result in brief discharges of flame out of the front of compressor against the direction of flight. But nothing sustained.

Pilot here. I predict that airlines are going to soft ground the Max while this gets sorted out. They might not take them out of service completely, but would not surprise me a bit if they rely on other equipment where possible until this gets sorted out. Better to take a hit on increased fuel costs that risk the loss of an aircraft and all on board.

all 737 max have just been grounded in china by government order: https://thepointsguy.com/news/china-grounds-737-max-aircraft...

Would you mind detailing the term "soft ground" for my own knowledge? Thanks

I think rpmcmurphy's middle sentence explained it: If you can, fly something else. If you're out of all flavors of "something else", then fly the 737 Max.

In situations like this, what does an airline do when most of its fleet is 737 max? More specifically, what happens to those flights on that day the announcement of planes being grounded was made?

There were 41k flights until May 2018 [1]. I was not able to find the current number but with 350 models delivered so far and 4 average flights per day that would sum up to ~500k flights in total at most (but more probably half of that due to ramping up the deliveries).

With 2 accidents the rate is now 4/million. That's at least an order of magnitude difference more than the average of the modern jetliners [2]

Of course, with two events it might be just bad luck but the similarities are concerning, as pretty much everyone observes here

[1] https://randy.newairplane.com/2018/05/22/737-max-a-year-of-s... [2] http://www.airsafe.com/events/models/rate_mod.htm

I'm not paranoid, but if I can avoid flights operated with the 737 MAX, I will. Two accidents in 5 months is a dangerously high fatality rate for a new jet.

I'd be curious to hear how many successful flights have happened since the 737 Max has launched, for comparison.

IIRC someone on airliners.net (not an authoritative source, but enthusiasts) said it was something like 150K. That sounds plausible, given they have produced about 350 of them and the first one flew (commercially) in 2017.

This guy on reddit claims to be a software engineer at Boeing and talks about how the system was mostly worked on by people that didn't understood how it worked, as the core was fortan and they were writing their patches on top of it in other languages.


Relevant (about the first crash):


"Those 189 who died were victims of Boeing’s redesign of its successful 737 aircraft, all about putting a bigger engine on it and trying to come up with a solution to correct the airplane’s changed aerodynamics. Boeing realized the redesign could lead to potential stalls. MCAS was the answer"

"Software combined with sensors would ensure the airplane would not tilt upward at an unsafe rate. The combination of the two would keep the nose at the precise right angle during all aspects of flight to prevent a potential stall.

Was this, in the end, a good design decision? No based on what occurred to this nearly brand new aircraft"

"Pilots can manually override the MCAS but cannot switch it off without switching off the flight computer. This fact in and of itself proved fatal to Flight 610, its crew, and passengers."

"Since the crash Boeing has sent out a safety warning with a procedure for cutting off MCAS in the event of an AOA sensor malfunction. A description of what a pilot would experience should the MCAS receive false data has been included so that he or she would know when to disengage the flight computer and manually take over flying the plane."

Moreover, bad software effectively working against the pilots, again connected to the stalls, was also the cause of this famous accident some 10 years ago:


"In an article in Vanity Fair, William Langewiesche noted that once the angle of attack was so extreme, the system rejected the data as invalid and temporarily stopped the stall warnings. However, "this led to a perverse reversal that lasted nearly to the impact: each time Bonin happened to lower the nose, rendering the angle of attack marginally less severe, the stall warning sounded again—a negative reinforcement that may have locked him into his pattern of pitching up", which increased the angle of attack and thus prevented the aircraft from getting out of its stall.[25]"

This reminds me of a link to a talk by Nancy Leveson that a guy linked to while taking Uncle Bob behind the woodshed for a shellacking because of some ignorant things he said about software safety.


If you don't want to watch an hour long video, she says most serious accidents and near misses happen not because something failed (and lets face it software 'bugs' are just another type of failure). But because bad interactions between properly functioning systems[1].

One of her comments is you need a system that watches for stuff like that. Lion Air Flight 610 crash happened because there wasn't a system that could make a determination that the pilots needed hard control over the aircraft. A safety system being repeatably overridden by the pilots for 11 minutes should have resulted in that system being shut down.

[1] One thing I got beat into me over the last 20 years developing sensor networks is how little information is actually available to systems like a MCAS system. That makes it's reasoning about the world brittle. Humans are better at managing path dependent state based on inane sources of information. The pilots utterly knew the aircraft wasn't stalling just by feel. While the MCAS 'knew' it was based on a messed up sensor.

> The pilots utterly knew the aircraft wasn't stalling just by feel. While the MCAS 'knew' it was based on a messed up sensor.

...except when the pilots get it wrong like they did on AF447 which crashed into the Atlantic Ocean when 'the crew failed to recognize the aircraft had stalled and consequently did not make inputs that would have made it possible to recover from the stall.' [1]. That accident was caused by a combination of equipment failure - iced up Pitot tubes - in combination with an erroneous reaction by the pilots.

[1] https://en.wikipedia.org/wiki/Air_France_Flight_447

AF447 crashed because the auto pilot handed control of the airplane over to the pilots when it was in the coffin corner with iced over pitot tubes[1]. And then stall warning system gave them very confusing information.

It's not really the same situation. In one the aircraft was absolutely flyable without instruments. The other it was not flyable without instruments.

[1] Absolutely last thing you want in that situation.

In human language: the centre of thrust of 737 MAX is placed such way that it is possible thrust pitch it into stall if the pilot completely misses that, or, on the opposite, if he overreacts and runs into oscillation.

I think that all what MCAS does could've been achieved by telling pilots to set certain trim at the takeoff, when the thrust is maximal, and let the regular "hard" anti-stall system handle that in level flight. Again, software people trying to "think" for their users.

This is so important… most airlines are inherently stable by design but the 737 Max requires software to be stable

No, it doesn't. The 737 max has software to prevent stalls in situations outside of the profile of normal flight. As does e.g. the A320.

Yep Apparently the main problem seems to be the fact there is a single point of failure (a single AoA sensor) and it could be resolved by having multiple sensors. Not that some sort of new automation is occurring than before.

The 737 max has multiple AoA sensors.

Having multiple sensors doesn't always help, as failures are correlated. For example, there was an Airbus A321 that had 2 of its 3 sensors get stuck in the same position due to icing.[1] The computer thought that the one working sensor was malfunctioning and disregarded it. It then engaged stall protection, dipping the nose and causing the plane to dive at 4,000ft per minute.

> The captain continued to hold “more than 50%” rearward stick in stable flight for a period, but with help from technicians on the ground, the crew was able to reconfigure the automation into the aircraft’s alternate control law, rather than its normal “direct” law. The action removed the alpha-protection checks and canceled the nose-down input. The aircraft then continued to its destination.

These failure modes tend to happen more with Airbus planes because their flight control systems default to overriding human input if the computer deems it unsafe. Boeing's flight computers will give more resistance in the controls, but they mostly won't prevent the pilot from doing what they want to do. The exceptions (such as auto-trim and stall prevention) can be disabled with by flipping a couple of switches.

1. https://aviationweek.com/commercial-aviation/german-investig...

True but 2/3 failing instead of 1/1 is still the better option. I’ve read the Max only used one sensor for the MCAS system.

But I’m not an expert on the subject so I’ll defer to the reports and more knowedgable people.

I recall reading somewhere that while the 737Max has two AoA sensors, only one of them is connected to the MCAS.

"The automatic trim we described last week has a name, MCAS, or Maneuvering Characteristics Automation System. It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA).

This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines."

Boeing only told pilots MCAS existed following the Lion crash, almost 18 months after the plane entered service


this is not true, where did you get this?


Maybe so, but please don't post shallow dismissals to Hacker News (https://news.ycombinator.com/newsguidelines.html).

If you know more, it would be better share some of what you know, so we can learn something. Alternatively, it's always fine to post nothing. When you do post, though, please make it civil and substantive.

>"Software combined with sensors would ensure the airplane would not tilt upward at an unsafe rate. The combination of the two would keep the nose at the precise right angle during all aspects of flight to prevent a potential stall.

This immediately struck me as completely negligent insanity. The thought of flying on a commercial airliner with no inherent stability, akin to a fighter jet, is horrifying to me. How this got past regulators is just mindblowing.

> The thought of flying on a commercial airliner with no inherent stability, akin to a fighter jet, is horrifying to me.

What hysteria. Relaxed static stability, or some degree of longitudinal static instability (not the same as "no inherent stability") is one potential option for reducing fuel consumption and emissions in future aircraft configurations (as correctly pointed out by multiple commenters, the 737 Max is not designed this way). To what degree that's safe depends on how the artificial stability is maintained in the presence of individual and common-mode failures. For a long time, orthodoxy and knee-jerk thinking precluded long-range transport on only two engines, or fly-by-wire, or primarily composite airframes. With decades of engineering and actual data behind them, these have now become standard.

Michael Crichton's Airframe treats this kind of knee-jerk thinking, and the dangers inherent in using terms like "stability" that have a huge gap between laypersons' perception and engineers' understanding.

This is a seriously misleading characterization of the 737 Max. If you read https://theaircurrent.com/aviation-safety/what-is-the-boeing... (the source of the article that 'acqq is selectively quoting) you will learn the following:

> MCAS is “activated without pilot input” and “commands nose down stabilizer to enhance pitch characteristics during step turns with elevated load factors and during flaps up flight at airspeeds approaching stall.

> Since it operates in situations where the aircraft is under relatively high g load and near stall, a pilot should never see the operation of MCAS.

In other words, the aircraft does not need MCAS for stability during flight in anything but exceptional circumstances. Normal flights should never have MCAS active.

This is not remotely similar to the aerodynamics of a fighter jet.

MCAS is a software mechanism designed to prevent stalls in extreme circumstances that can be overridden with the same method used to disable auto trim on previous models of the 737. The A320 has software to prevent phugiod motion in exceptional scenarios, except the A320's mechanism cannot be overridden by the pilot.

I don't care if you choose to never fly on a plane again, but don't spread this misinformed hysteria.


Crossing into personal attack will get you banned here. Please review https://news.ycombinator.com/newsguidelines.html and don't do that again.

Accusing someone else of astroturfing or shillage without evidence is particularly out of line.


The comment you are responding to addresses the claim that the 737 max is not passively stable. It is less safe than other aircraft, but not because it requires active control for stable flight in any manner comparable to a fighter jet.

I'll direct you to some portions of my other comments that you seem to have overlooked:

> airlines and pilots were not informed well enough about MCAS

> previous auto trim systems could also be "out muscled" just by pulling back on the yoke without actually switching on the manual override.


> polluting this thread with lies

I'm pretty sure everything I've posted on this thread is either true or obviously an opinion. If some things are not true, please point them out specifically so that I can correct them.

Nowhere have I said that the lion air 610 accident only happened because of poor maintenance or pilots actions, but it is undeniably true that with different pilot actions and aircraft maintenance the accident would not have occurred.

chill, pal - you're carastrophizing something you don't understand

They should ground all 737 Max (350 have been built so far) until investigators understand fully what caused these two crashes and a fix is implemented (if it is proven that there was fault in the plane itself).

It's highly unusual for a plane that has been in operation for only 3 years to have two crashes shortly after takeoff.

I certainly won't be taking any flights in them until a thorough explanation emerges of what happened on these two flights.

And Boeing PR should stop saying that the planes are safe (they recently put out a statement affirming it's safety). At best, they should say "we don't yet know, and are investigating".

I understand and agree with the suggestion that the whole fleet be grounded, but isn't personally avoiding the planes an overreaction? While the chance of another fatal crash in the imminent future may be high, surely the chance that you would be on it is still quite low.

If you think the plane should be grounded, then being personally happy to fly on it doesn’t make much sense. Other planes are available.

You're mixing up two different probabilities. The chance of more fatalities is high, which justifies grounding the fleet, but the probability of a crash of the particular plane a particular person is on is still rather low. Not as low as other planes, but still low.

Going on a 737 MAX plane: X% chance of dying

Going on a non-737 MAX plane: Y% chance of dying

Given these two accidents, X > Y

Why sign up for a higher chance of dying?

Is the chance of dying on a 737 Max flight higher than the chance of dying driving to the airport? Have you considered walking instead?

That is: If both X and Y are low enough, it's not worth the inconvenience to get Y instead of X.

Why drive anywhere you can fly? Driving means always signing up for a higher chance of dying.

If both are very small, then why wouldn't some other factor like minor convenience wash out the minor safety concern? I don't know about you, but I pick my flights by airline, time, and price. I wouldn't degrade any of those for a very small increase in safety.

I believe the point is that we don't _know_ that it's very small (_if_ it's a design flaw, it could be significantly higher), and there are (generally) viable alternatives, so it's needless extra risk

Right now the MAX version is at least an order of magnitude less safe than the previous generation (put some rough estimated in another comment)

Airliners are exceptionally safe as a general rule. Small GA planes are TWO orders of magnitude less safe. Would you avoid a flight in a single engine prop plane? I wouldn't. While it's a certainty that many people will die in small plane crashes this year, it's still unlikely that the particular plane I'm on will crash.

I think this is a classic case of people overreacting to dramatic but unlikely risk. And to be clear, I support grounding the fleet.

Showering and then driving to the airport both are have a >> X chance of you dying before you even get on the Max.

Being aware of the general standard of software devs + teams, it is terrifying to think that my life is in their hands.

Thats not the case with structural or civic engineering say. The more I know about that the safer I feel.

There's also the misplaced emphasis on speed. Software safety and verification courses are considered "advanced" level. CS undergraduates are now led to believe that logic is a bore, and is old-fashioned computer science. Of course, with the advent of machine learning, "It Works!" is now considered as enough proof, so that's a whole new level of crazy.

Permit me to point out that "It works!" is not considered enough proof for flight software.

How long does it take to ground an aircraft assuming the decision to ground is made?

For an airliner, decision could be implemented in under 24 hours if a country’s civil aviation authority (FAA for the US) decides it’s an emergency. More likely, they’d permit ferrying to maintenance bases, and very unlikely to emergency ground the aircraft absent a finding of same root cause, even if preliminary. I’d be surprised if they took a fleet wide emergency grounding action.

I also doubt that the aviation authorities would ground the 737-8 without more evidence of a design flaw, but it's worth noting the FAA and other national authorities did ground the 787 for three months between January and April 2013 as a result of battery fires.

Is there any recent history for FAA to issue an emergency grounding for one type of aircraft?

The only example I know is DC-10.

Perhaps Concorde, although I don't know if the emergency grounding was mandated by the authority or voluntary.

As I recall one of the problems with the Concorde was that the existing fleet was getting quite old and spare parts were hard, if not impossible to come by.

The incident in Paris may have sped up the process of decomissioning the plane, but it would have happened anyway eventually.

All was not lost. A lot of the more visionary aspects of that plane, were implented into later Airbus models (i.e. the glass cockpit derives directly from the Concorde).

An outstanding (if slightly outdated) discussion about all things Concorde can be found here: https://www.pprune.org/tech-log/423988-concorde-question.htm...

Airlines can ground a new aircraft pretty bloody fast. Qantas grounded its A380 fleet within a couple hours of QF32 landing in 2010. Havoc, definitely, but every major airline will take havoc over an accident any day of the week.

On 9/11 they announced that all flights were grounded in less than an hour, and from that point it was just however long it took for each plane to find the nearest safe place to land.

IIUC, preliminary investigation said Lion Air plane wasn't airworthy before its flight and basically blamed Lion Air for poor safety processes: https://wkow.com/news/top-stories/2018/11/28/lion-air-crash-..., https://www.indonesia-investments.com/news/todays-headlines/...

OTOH, I've also seen independent analysis that suggests Boeing was to blame due to the poor disclosure of important changes in the system.

What can explain such a difference in the primary messages from investigators and from analysts?

Boeing failed to disclose important changes in the system. And Lion Air's maintenance rendered the plane unsuitable for flight. They can both be contributing factors to the earlier crash.

If the EA flight was caused by the same sensor problem as the LA flight, then it would appear that Boeing's changes were the primary (and superseding) cause of the earlier crash, rendering Lion Air's non-maintenance moot from a legal point of view (in the US, for purposes of assigning damages).

Oh so it could imply that Boeing is responsible for two independent contributing factors: sensor malfunction and failure to disclose system changes, correct?

Wouldn't Lion Air processes still remain relevant as a third contributing factor, since fixing any of these factors could have reduced the probability of the accident?

Sensors fail, at some point that becomes the airline's responsibility to maintain and not something which can be blamed on the manufacturer. Lion Air had reason to believe the sensors were malfunctioning and they still flew the plane unfixed.

Almost any air crash is due to a sequence of factors. Both things can be true.

> preliminary investigation said Lion Air plane wasn't airworthy before its flight and basically blamed Lion Air for poor safety processes

Your own links say no such thing, and directly contradict your claims e.g.:

> One of the angle-of-attack sensors on the airplane's fuselage was replaced after the airplane's penultimate flight - from Bali to Jakarta - after the Lion Air plane experienced malfunctioning data readings. Investigators therefore said the plane had not been airworthy during its last two flights.

How did you get from repaired to "wasn't airworthy?" Also the actual report doesn't "blame" Lion Air, it simply lists the facts. It is far too early to be assigning blame, and I'm sure there will be enough to go around (including the regulators themselves).

Wonder if many airlines just made a habit of flying with broken AoA sensors, which until the 737 MAX was easy to get away with.

Well, the manufacturers and certification define a MEL[0] which must be adhered to and outlines what equipment needs to be functional for a flight. If the MEL specifies one AoA out is acceptable then you can bet the airline will fly with it until they can swap it out depending on maintenance constraints.

[0] http://www.aopa.org/asf/publications/inst_reports2.cfm?artic...

It is perfectly common to fly with inoperable equipment. There are equipment lists that define minimum numbers and mitigation. Of course that doesn't mean the advice is followed or flawless.

That would still fall on Boeing, it would be their responsibility to make it clear that what was acceptable in the past (broken AoA sensor) is not anymore.

I doubt any company would have supported that configuration officially in the past. That it happened to work is another matter entirely.

One of the engineering improvements that (as an armchair viewer) believe needs to be made is better communication of auto-pilot state to the crew. ANY deviation from designated human input needs to be clearly communicated to the pilots so they know what the hell is doing it and if necessary which system(s) to disable to regain full manual control.

I have read that the reason pilots were not informed of the software and procedure changes is that part of Boeings sales pitch for the 737 Max was that it would require minimal re-training of pilots who had already been flying earlier 737's.

Not quite. Boeing said they didn’t want to deluge pilots with information when training them on the new plane and that existing manual procedures cover how to deal with the problem by disabling a system. Aka they didn’t see changing training or the manual as an immediate solution.

But the final report of the first crash isn’t even out yet. Which I find interesting considering all the finger pointing going around (even by arm chair “concerned citizens” in this thread).

Assuming we even know what happened I doubt the solution will end up being a training thing and most likely updates to the software, UX, and/or the addition of back up AoA sensors.

> But the final report of the first crash isn’t even out yet. Which I find interesting considering all the finger pointing going around (even by arm chair “concerned citizens” in this thread).

If a supposedly-very-safe type of hardware kills a bunch of people twice in similar-looking incidents, that is very worrying.

It's a rational reaction to look at these incidents and go "yeaah, I'm going to try and avoid those planes" regardless of whether official reports are out or not.

It’s interesting to observe that, if this is indeed caused by a failure in the stall prevention system (and I say “if” since it’s certainly too soon to draw conclusions), the media and discussion around it seems to gravitate towards disabling the system or avoiding the aircraft entirely.

But when we think forward to the inevitable autonomous vehicle accidents that will occur, the conversation turns to how many lives they’ll have saved, and how much safer they’ll be.

Is there a known psychological phenomenon for “negative hindsight, positive foresight” that I can go learn more about?

The problem is that you can't disable that system: the aircraft is not certifiable without, that is to say the risk of stalling is considered too high without that system. Because that system may have caused two planes to crash doesn't mean that it didn't prevent the ~350 other 737-MAX flying from stalling.

So if the MCAS is indeed the cause of that crash, I expect fleet grounding until the system is fixed. Assuming it is fixable, which I think it is, but might require more than just a software fix.

> But when we think forward to the inevitable autonomous vehicle accidents that will occur, the conversation turns to how many lives they’ll have saved, and how much safer they’ll be.

Driving to the airport is orders of magnitude less safe than flying. If a malfunctioning automatic system is decreasing the reliability of flying, that's a huge problem. However, I'd wager that even an autonomous car that's only just able to pass a driver's exam would be significantly safer than a human driver because it would _follow the rules_ and _not be distracted_. Even if that system isn't perfect, it's probably still better than an experienced driver.

Except we test humans with tests designed to show that a human who is capable of generalizing knowledge can do a few things that prove they can do more things than that. If the AI isn’t capable of that then just being able to pass the drivers test might create a very incapable AI

This is what scares me about the push toward fly/drive-by-wire.

At some point your designs start breaking into envelopes where the machine cannot be considered safe once the automated systems fail, making your pilot/highly trained human being powerless in the face of catastrophic system failure.

An uncontrollable tool is not a tool, but a coffin waiting to happen. I don't think any type of "routine" transit system should be designed in a manner such that it so thoroughly overwhelms a human crew's workload that it should be so dependent on automation that it cannot be certified otherwise.

To reword: if it can't be safely flown with the computers off, it probably should not be a design we allow for people transport. Markets be damned. When your margins include human lives lost, economy needs to stop being your primary optimization. Dollars should only be important after you stop being a corpse factory.

Interesting point.

I guess whether it’s human error at the hands of the pilot/driver, or human error at the hands of the engineer/designer, we can never fully remove it from the equation.

Should we just give up? Seems the best we can do is try and mitigate risk, and automated systems condense this risk down into fewer points of failure (i.e., there are less engineers than users!).

The difference is, the pilot is one person, and his life is in danger, so he is dead serious. Designers/engineers work in teams, supervised by managers and driven by market. Responsibility is diluted to the point that evereyone feels they did nothing wrong, although the results are catastrophic.

I am sure that an autonomous system that does not have a manual override will have the same pushback against it.

In a way similar to how the third leading cause of death is medical errors, in the future, one of the leading cause of death will be computer bugs.

How long does it take for the plane to crash plane after an over-thrust induced stall condition? How long does it take to crash the plane after an errant MCAS induced nose-down event (which might not be overridden by pilot response)?

If it ends up being due to faulty sensors they need to add a big disable all assistive software systems switch. It needs to be easy to access switch not something you have to go through 5 menus.

There already is a switch to disable auto trim. The pilots on the flight prior to 610 used it, as trained. The pilots on 610 did not.

The switches are right here in the middle of all 737 consoles and instantly disable automatic stabiliser control:


Many comments are debating where blame for the incident lies - some suggesting that Boeing is simply pushing blame onto the carrier and not admitting fault. This very well could be the case, but I do wonder why the crashes of this plane (to my knowledge) have all occurred with carriers that have less than stellar safety records. If this crash had been a European, American, or other airline with a top safety record I would have significantly greater suspicion of the plane model and Boeing specific problem and not just poor safety procedures and training with the airline.

Ethiopian Airlines does not have a poor safety record. They fly all over the world and allowed in Canada, US, Europe, etc. This isn’t the same as the Indonesian crash. People always assume it’s a bad airline because it’s from Africa, but that’s not the case.

It could be that the interaction between the two factors (poor safety practices by an airline and the lack of disclosure by Boeing) increases the risk.

Suppose that steering in a new car model tends to drift from the straight line slightly more than usual.

Attentive drivers would easily correct for it, and would merely find it annoying. For them the accident rate would increase very little if at all.

OTOH, the accident rate might go up more noticeably for those who text while driving, since they often won't notice the drift until it's too late.

When you look at the accident reports where steering drift was a factor, you'll see that most of them involved distracted drivers.

Google the Swiss cheese theory of safety. Very seldom an accident is caused by only one thing going wrong, and very seldom is it caused by only crew error or only technical failure.

Going from “Ethiopia” in the airline’s name to an assumption (against factsv) of a bad safety record is textbook racism.

I think going from an entire continent that has a seriously bad safety record and would be EASY to assume (if you didn't know better, which I didn't) that a member country of said continent probably also has safety and process issues to "you're a racist" is a pretty big overreach. People are WAY too cavalier with that branding of people's intentions. You in no way know me, where im from, who I am... and yet you call me that? Tsk tsk... shame on you.

It is a little off topic, but I hate flying the 737. The way it is shaped makes it feel tiny on the inside even when compared to the much smaller Embrarer E175. It seems to be the only large airliner you will find on domestic flights in the U.S. and it makes me take the bus or drive if I had a choice.

If Boeing were to give the 737 the 787 treatment the benefit to the flying public, airlines, environment, etc. will be huge but as long as Boeing can sell the 737 without a real upgrade it is a cash cow for them and they'll never stop making it.

"If Boeing were to give the 737 the 787 treatment the benefit to the flying public, airlines, environment, etc. will be huge but as long as Boeing can sell the 737 without a real upgrade it is a cash cow for them and they'll never stop making it.'

The MAX 8 is very literally the 737 being given the 787 treatment. What are you asking for here? 10 abreast seating? Then it would just be a 787...

> The MAX 8 is very literally the 737 being given the 787 treatment.

Not even close. The MAX is as basic a re-engining of the 737 NG as possible. It was an explicit design goal to minimize differences, to the point where pilots don’t even need simulator work to be approved for the MAX. (This was the purpose of the MCAS system that doomed the Lion Air fight, to make the MAX handle as similar as possible to the NG even in almost-stall conditions).

And the 737 NG is itself a refresh of the late-60s 737. Much about the aircraft is unchanged since the 60s: the fuselage cross-section (slightly smaller than the late-80s A320), door arming/opening, lack of RAT, etc.

Much of the cockpit improvements since the 80s (integrated EICAS) are missing from even the MAX, and none of the 787 innovations (composite fuselage, bigger windows, no bleed air/all-electric) were even close to coming to the MAX.

Yeah the 787 is a very different plane, and imo a lovely flying experience as a passenger. Less noise, lower cabin altitude, spacious cabin, modern passenger cabin tech...it's great! I hope it's safe, but frankly after whats happened recently, I have my doubts.

There's a fear that a carbon fiber body won't perform as well in an Asiana Airlines Flight 214-type crash because it's apt to shatter rather than just deform like aluminum.

Yeah reasonable, but i wonder if it’s also less likely to have stress fractures that could result in unpredictable failure?


In theory, but aircraft are rated for and maximum number of takeoff and landing cycles so that stress fractures aren't a problem while they're in service.

Carbon fiber could change some of the economics around that, but I'm not sure if the airframes wear out from stress before or after efficiency gains make new planes more desirable.

What is bad about the 737 is the circular cross section which makes it feel cramped. A truly modernized 737 would go oval. As it is my neck muscles cramp up just thinking about going into a 737.

Plenty of US airlines fly the A320 and 757 domestically, and you'll even see the occasional 767, 777, and 787. AA's transcontinental A321-T is fantastic!

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