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Report Blames Faulty System, Pilot Error for Boeing 737-500 Crash in 2021 (seattletimes.com) 86

346 people died in two separate crashes of the Boeing 737 MAX — one in 2018 and one in 2019. And then in 2021, a Boeing 737-500 crashed in Indonesia, killing all 62 people on board.

Thursday Indonesia's national transportation safety committee (KNKT) released its final report on that 737-500 crash. It found that after takeoff the plane's autothrottle system (which automatically adjusts power to the jet's two engines) became stuck on the right engine, "as a result of friction or binding within the mechanical system," according to the Seattle Times. The newspaper also notes that the same system "had repeatedly malfunctioned on the aircraft before the crash."

The report also blames an inadequate response from the pilots. As the jet climbed away from the runway in Jakarta and the pilots adjusted the autopilot mode to reduce thrust, the autothrottle duly eased back power to the left engine but the right engine continued at full power. The resultant asymmetric thrust caused the plane to turn to the left even as the pilots steered the control wheel to the right and the autopilot followed by moving control surfaces on the wing to roll right. Another system on the plane designed to monitor for asymmetric thrust also malfunctioned and delayed disengaging the autothrottle as it should have.

But as this was happening, the pilots were unaware of it. The pilots should have seen from the instrument panel attitude display that the plane was deviating from its flight path to the left. And they should have noted the right thrust lever not having moved backward like the left lever, alerting them to the asymmetric thrust. They apparently missed both clues.

Just under 5 minutes after takeoff, as the jet banked steeply left, a warning alert sounded in the cockpit: "BANK ANGLE." Two seconds after the alert sounded, at an altitude of 10,700 feet, the pilot in command disengaged the autopilot system to take manual control. This pilot, 54 years old with almost 18,000 hours of flight time, half of that in a 737, clearly didn't realize that the autopilot had been compensating and masking the effect of the asymmetric thrust in the engines. With the autopilot gone, the countering forces from the control surfaces on the wings were removed and "the yaw and roll forces of the asymmetric power rolled the aircraft to the left," the investigation report states.

The pilot was so unaware of what was happening that he steered the control wheel further left instead of right, which "increased the roll tendency of the aircraft to the left." The plane rolled more than 45 degrees left and went nose down.

At that moment, the autothrottle finally disengaged. But it was too late to recover. The flight data stopped recording as the plane crashed into the sea.

The report faults the pilots for their lack of recognition of the situation.

It blames "pilot automation complacency" (overreliance on the automated system) and "confirmation bias" (believing that the plane was steering right as commanded, when in fact it was rolling left).

The Indonesian safety authority found that Sriwijaya Air provided "inadequate" training for its pilots in upset recovery, which means righting an airplane if it inadvertently stalls, rolls or pitches to deviate from the intended flight position. Indonesia now mandates detailed upset recovery training for all airline pilots.

The KNKT report also states that the system that was supposed to monitor the 737's autothrottle for asymmetric thrust and disengage it — the Cruise Thrust Split Monitor — may have been misrigged by maintenance personnel, or its failure may have been due to a sensor fault providing an incorrect value for the positions of the control surfaces on the wings to the autothrottle computer.

The report notes that Boeing is issuing a bulletin to all 737 operators requiring repetitive inspections of the control surface sensors. An Airworthiness Directive that will make this mandatory is pending from the Federal Aviation Administration.

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Report Blames Faulty System, Pilot Error for Boeing 737-500 Crash in 2021

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  • No pilots on board (Score:4, Insightful)

    by Tailhook ( 98486 ) on Monday November 14, 2022 @03:51AM (#63049639)

    Only autopilot operators. Same story over and over.

    • It also possible that the throttle was stuck so bad that the pilot could not move it, despite his best efforts. However, since the pilot is dead, it is safe to blame him for everything.
      • by Ed Tice ( 3732157 ) on Monday November 14, 2022 @05:32AM (#63049751)
        I agree with you that it's easy to blame "pilot error" in many instances especially when the pilot is dead and can't argue. But we do have flight recorders in these situations. The autopilot/auto-throttle was left engaged much longer than it should have been in such a situation.

        In the case of the 737-Max, I've argued quite aggressively that the fault was of the aircraft manufacturer and blaming the pilots is ridiculous even if they made mistakes. They can't possibly handle a situation where a secret piece of equipment fails.

        However, the OP's post is pretty valuable here and I hope the mis-moderation is corrected. We saw in the Ethiopian airlines 737-Max and the crash here that pilots' first instinct when a problem arises is to get the automation engaged under the premise that it will solve everything. That's a problem. If something goes wrong, the instinct should be to disengage as much automation as possible and do stick-and-rudder flying because it simplified the situation. But to have that instinct you need to have skills and confidence in your own abilities.

        You also need to fly in a safety culture where you don't fear getting penalized for taking manual control, turning around, and putting the plane right back down at the departure airport.

        It's often the case that pilots are given three hard problems to solve and three minutes to do so. They get two and half of them correct and the crash is called "pilot error." But in this case, the auto-throttle was malfunctioning for a full five minutes and noticeable via the flight path, the instrumentation, and the physical position of the throttle levers. The pilots didn't notice until a warning signal sounded and then they reacted in a panic.

        Being a pilot is very hard because most of the time the plane largely flies itself but you need to avoid getting lulled into complacency and constantly be ready to take over. And then taking over requires immense skill. That's part of the job.

        • by DarkOx ( 621550 )

          I am not a airliner pilot or even a pilot. Are you out of curiosity? I am not trying to be critical or contradictory here just looking at other experiences and wondering if this is attitude or technically informed.

          One possible analogy (and maybe its not - would like to hear from a pilot) is a car on packed snow/ice. There are lot of people that go around thinking 'they' can do better at correcting the situation than ABS + stability control. This is by and large false. Even a professional driver can as a r

          • If the ABS is malfunctioning, you are better off turning it off. You can't generally do that on current cars, but if for example, ABS is only working on the left, not the right, as soon as it engages, you will go into a spin.

            If the ABS *might* be malfunctioning, and you have experience driving on packed snow or ice, you are still on average better off turning it off. I drove for thousands and thousands of miles in the snow before ABS and never had an uncorrectable problem, so it can be done.

          • I am not a pilot. They do not let us blind people fly planes. My only qualification is that I have worked on aviation software. You are not wrong that automation-first is often better. It's generally more fuel efficient and produces a better and safer flying experience which is why automation is used so heavily.

            The issue is that, once it has been determined that something is not functioning properly (i.e. failed sensor, et cetera), one needs to assess the situation and be able to take over. The so

          • You have misunderstood the problem ABS tries to solve. ABS tries to solve the problem of inexperienced drivers attempting to maintain control on unfamiliar surfaces.

            In almost all cases, an inexperienced driver, when encountering slippery surfaces, will jam on the brakes until they slide into whatever is in front of them. ABS helps in this case by making the actual stopping distances shorter, thereby mitigating at least some the damage caused by an inexperienced driver.

            However, an experienced driver, u

        • by FeelGood314 ( 2516288 ) on Monday November 14, 2022 @10:59AM (#63050427)
          Read a Canadian Transport Safety Board accident report. They never blame human error. They blame the things that lead to the human making the mistake. Humans make mistakes all the time. You have to design a system that:
          1. Makes it hard to make mistakes
          2. Makes it easy to recognize you made a mistake
          3. Make it easy to fix a mistake
          4. Minimize the impact of a mistake

          Autopilots and eventually self driving cars are good things because people suck at doing things over and over again without making mistakes. We need to figure out how to ensure humans still have the skills needed when the autopilot fails. The Indonesian report is a good one because it makes general recommendations that will save lives in the future.
      • by N1AK ( 864906 )
        You're exactly the sort of person who perpetuates and encourages baseless conspiracy theories because you won't let the fact your ignorant in a field stop you commenting on it but you have nothing of technical value to add. Black box data includes cockpit comms so if the pilot(s) were aware of what was going on there would be plenty of evidence from both inputs and audio communication. The reviews are done in large sessions including representatives of airlines, manufacturers, and pilots; afterwards plenty
      • by Tailhook ( 98486 )

        It also possible that the throttle was stuck so bad that

        It's also possible that angry unicorns broke into the cockpit and poked out the crew's eyes with their horns and then sat on the throttle. Except neither that nor the fiction you imagine are in the analysis. What is in the analysis is clear evidence of shit maintenance and shit piloting. Dealing with equipment failures are what the pilots are for. If we could rely on the gear then we wouldn't have pilots.

      • by bobby ( 109046 )

        I haven't had time to read the story, so take this with that in mind, but I would expect if the throttle lever was stuck, the CVR would have some pilots' comments about that?

    • Re: (Score:2, Troll)

      by Drethon ( 1445051 )

      Only autopilot operators. Same story over and over.

      Did anyone ask Elon how the system should be used?

    • by Petrini ( 49261 )

      Maybe - surely certainly - some pilots, but not all. My sister's father-in-law is was a military, then commercial pilot for decades. It was a calling for him, and many of his colleagues. He had a healthy disdain and skepticism for auto-anything. Auto-pilot, auto-drive, auto-brew coffee...

      He often tells us about things non-pilots don't think about, like: if one member of the flight crew leaves his/her seat (e.g. to use the head), the other has to don and activate an oxygen mask. Just in case. He'd poin

  • I have read so often that this kind of crash can only happen in an Airbus because the sidesticks and the thrust levers in an Airbus are not moving. This is a counterexample for the thrust levers, there are two counterexamples for the yokes.

    https://aviation-safety.net/wi... [aviation-safety.net]
    https://en.wikipedia.org/wiki/... [wikipedia.org]

    • by Richard_at_work ( 517087 ) on Monday November 14, 2022 @04:25AM (#63049685)

      Boeing likes to make huge changes to aircraft without informing pilots or requiring additional pilot training - because thats an expense that would cost it sales.

      For example, take a look at the Kegworth air disaster in 1989, involving the then brand new Boeing 737-400.

      A faulty engine was the ultimate cause of the crash, but major contributing factors included redesigned throttle controls (with no independent autothrottles - so each engine can be set to one setting on the throttle but actually be at 90% and 10% with no obvious indication), redesigned air conditioning systems (swapped the engine the bleed air was taken from, so pilots detecting smoke in the cabin thought the wrong engine was at fault) and a redesigned cockpit instrument layout, which moved things like engine vibration levels to a place pilots were not expected to look at.

      If none of the above was changed, or the pilots were retrained on the new model, the flight would have landed safely albeit with one engine shut down.

      Instead, it crashed short of the runway.

      • This is a crisis of change management. There's good reason for change, especially instrument layouts. The airline / military industry is in the absolute forefront of effective HMI designs and improvements. The major issue is the training part.

        One should note that's not just Boeing. The damn airlines are the ones doing a lot of corner cutting, and in the case of the MAX recently were the ones actually asking Boeing to design a plane so they wouldn't need to retrain pilots.

        There's plenty of blame to go around

      • by 6Yankee ( 597075 )

        Exactly this. One of the lessons we were supposed to have learned from Kegworth is that you can't just give pilots some stuff to read and then have them jump straight into a new variant with no sim time. This lesson had clearly been forgotten by the time the MAX came along.

    • by nagora ( 177841 )

      I have read so often that this kind of crash can only happen in an Airbus because the sidesticks and the thrust levers in an Airbus are not moving. This is a counterexample for the thrust levers, there are two counterexamples for the yokes.

      https://aviation-safety.net/wi... [aviation-safety.net]
      https://en.wikipedia.org/wiki/... [wikipedia.org]

      Right. Safety feature isn't 100% reliable so it's worthless, yeah?

      • No. You bought Boeing's marketing line, nothing more. Boeing not having a fly-by-wire system is not a safety feature. It was just their attempt at negative marketing competitors who implemented a different system.

        • by nagora ( 177841 )

          No. You bought Boeing's marketing line, nothing more. Boeing not having a fly-by-wire system is not a safety feature. It was just their attempt at negative marketing competitors who implemented a different system.

          So you don't believe that having visual and tactile feedback is useful? Please explain.

          • by ceoyoyo ( 59147 )

            As you pointed out, it's a double edged sword. The moving throttles give extra feedback, but they can get jammed. It's not the first time a jammed throttle level and autothrottle has caused an accident.

            At the same time, with a fly by wire system you can provide moving controls and force feedback if you decide that's important.

            A bigger issue is probably the 737's use of the older master caution system instead of EICAS. EICAS shows warnings in a central location and identifies or shows checklists for dealing

          • So you don't believe that having visual and tactile feedback is useful? Please explain.

            a) there is visual feedback to what the copmuter is doing, just not moving the control input. In either case you need to be trained to know where to look for your visual feedback (and pilots don't routinely look down at their throttles, especially during a crisis)
            b) tactile feedback is largely useless for pilots, it just fights them. Additionally there are too many control elements to have tactical feedback about all current actions being undertaken.

            If you want an example of this, there's a story on Slashdo

  • The helpful gadgetry is there, so it's going to be used. Lots of pilot training to NOT rely on all that stuff is going to be a tricky message, because should the pilot NOT use it and the plane comes down, then that's pilot error too.

    Notice that the complaint really is that despite 9000 hours of flying a 737 the captain didn't have a full mental model of every gadget in use so "didn't realise" that one gadget was doing that one thing and with it disabled it was no longer doing that one thing. Along with all

  • Not a MAX crash (Score:5, Insightful)

    by orzetto ( 545509 ) on Monday November 14, 2022 @04:38AM (#63049697)

    Why does the summary lead with the MAX crashes, when the entire article is about a non-MAX crash, completely unrelated to MCAS and other Boeing shenanigans?

    It almost appears as if someone tried to juxtapose the MAX crashes (very much the fault of Boeing) to another crash caused by pilot error, thereby giving the impression that eventually Indonesian authorities found out that it was really the pilots' fault for the MAX crashes all along. At least I got this impression in my first cursory reading.

    • They try to blame everything on pilot error!
      • by tlhIngan ( 30335 )

        They try to blame everything on pilot error!

        Well, historically it's something like 70% of accidents have a human component.

        It's really a problem caused by the fact that the modern airplane is extremely reliable that failures of mechanical components are a rarity, at least to the point where they cause an accident. There's enough redundancy that even when a system fails, the backup usually just takes over to ensured continue safety of flight.

        Accidents like the MAX MCAS which was caused by the angle of attack

      • In this case, both of the guys on the flight deck didn't do their job and fly the plane or use their instruments.

    • by elcor ( 4519045 )
      you're right. it's almost as if they tried to click bait us.
  • To the world of third world maintenance and third world pilots. Don't fix anything, don't train anybody.

  • "It blames "pilot automation complacency" (overreliance on the automated system) "

    Which is deadly in a Boeing.

  • Until you are at cruise altitude, DON'T use all that automation nonsense. Hell, I won't even use the cruise control in my passenger verhicle. Once you are at altitude, wings level, you want to use the auto pilot that's fine. But for takeoff & landing, turn that crap off.
  • until it was proven that they were lying their arses off.

    let's see what the pilot's association has to say on this.

  • It's Slashdot, so a car analogy: Imagine a big 8 cylinder muscle car with a a silent engine. It will have a foot pedal for the throttle ('the gas') to increase power to the engine. It will also have a tachometer to see how much actual power or throttle is being delivered from the engine. If the driver takes their foot off the pedal and there is a fault in the linkage between the gas pedal and the engine throttle and the engine doesn't disengage, the driver will see it on the tachometer. The driver can easil

  • The report faults the pilots for their lack of recognition of the situation.

    It blames "pilot automation complacency" (overreliance on the automated system) and "confirmation bias" (believing that the plane was steering right as commanded, when in fact it was rolling left).

    Did either of the guys on the flight deck look at the artificial horizon? I doubt it because mistaking a roll left from a roll right is easy to determine if you look at the damn instrument.

    As the jet climbed away from the runway in Jakarta and the pilots adjusted the autopilot mode to reduce thrust, the autothrottle duly eased back power to the left engine but the right engine continued at full power. The resultant asymmetric thrust caused the plane to turn to the left even as the pilots steered the control wheel to the right and the autopilot followed by moving control surfaces on the wing to roll right. Another system on the plane designed to monitor for asymmetric thrust also malfunctioned and delayed disengaging the autothrottle as it should have.

    There are also gauges in the middle of the console one set for each engine that shows you engine power, temperature, etc. You can visually see if one engine is pushing too hard at a glance, you just have to look.

    18000 hours? No, this was a guy who didn't train and didn't trust his instrumentation which could have avoided

  • There's some sort of cultural issue affecting Asian airlines. The airplane in question had thirty-two reports of autothrottle malfunction. That's too many. There was no proactive initiative to take the aeroplane, diagnose and repair the issue.

    The pilots had no skills. Nobody was monitoring the airplane flight path. When the asymmetric thrust issue triggered a bank angle warning, the pilot banked the airplane further in the wrong direction.

    Nobody noticed that one throttle lever wasn't moving with the other.

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