8 ms·

Sorry for another comment, but in my research into the topic the saddest bit of information I've seen is the image of the black box data for the flight (the fir

Sorry for another comment, but in my research into the topic the saddest bit of information I've seen is the image of the black box data for the flight (the first crash): https://i.imgur.com/WJuhjlO.png https://i.imgur.com/WJuhjlO.png You can see from the graph that in the final minutes and seconds, the pilot put insane amounts of force on the control column (aka the yoke) to try to pull the plane out of the dive - to save the 189 people on board. But no, MCAS was overpowering and lacked the documentation for the pilot to try anything else. Also interesting to see is the amount of times the pilots bring the nose up, only for MCAS to kick in and force the nose back down. 26 times. All data from this Seattle Times article, which was written before the second crash occurred: [1] https://www.seattletimes.com/business/boeing-aerospace/black-box-data-reveals-lion-air-pilots-struggle-against-boeings-737-max-flight-control-system/ https://www.seattletimes.com/business/boeing-aerospace/black...

Theodores 7y ago
> Also interesting to see is the amount of times the pilots bring the nose up, only for MCAS to kick in and force the nose back down. 26 times. That is awful. I heard that MCAS kicks in for ten seconds and then goes off for five seconds. So that must have been terrifying, for the pilot to think he has it under control for the death wish of MCAS to try again, and again and again until it gets its own way. When you look at how much has been invested in Homeland Security over the last seventeen years it is doubly tragic. It wasn't terrorists that we needed to fear, it was hasty management decisions at the FAA.
- groby_b 7y ago
  1) Let's place the blame where it belongs, Boeing. The FAA didn't force them to rely on a single sensor (in fact, given that MCAS can have hazardous consequences, two are mandatory IIRC). The FAA didn't force them to have MCAS three times the control range that's mentioned in the specs. The FAA didn't force them to not mention MCAS at all. 2) While this is certainly a tragic incident, it has nothing to do with homeland security existing or not. It's not like the autopilot suddenly decided to use planes as weapons. Apples and oranges.
  - rdiddly 7y ago
    2) That is precisely the point though. We went crazy preventing apples when the threat was oranges.
    - Theodores 7y ago
      Thanks for that, the point has not been made in mainstream media, but time will reveal what a farce the Homeland Security thing was, a project fear to keep everyone believing what they have been believing. Meanwhile the FAA has been changed from being the helpful body it once was. Blaming Boeing is one thing but we know from our own coding work that you don't have the programmer test and deploy mission critical stuff, you get someone else to do it. It is a team effort. In code if you cut the people out that do all the testing and just ask the programmers to deploy stuff when they want to it goes wrong. I am not cutting Boeing slack in this, if you go back to the programmer analogy, you still get your code written to best practice before you put it anywhere near the testing and deployment people.
  - iforgotpassword 7y ago
    1) then why didn't they force them to use input from both? Why give this shitty design green light? Why outsource parts of the certification process to Boeing, the same company who's plane is to be certified? Because of 2) obviously. All the money is gone. No budget for rigorous testing and validation of specs.
    - groby_b 7y ago
      Outsourcing of certification predates homeland security - see e.g. mid-90s reporting on the 777 certification[1]. In fact, the idea of outsourcing parts of the certification process started IIRC in the mid-1940s. What did happen past 2001 (but not due to budget pressures) is that the airline manufacturers got the authority to appoint their own designees, and were allowed to self-certify. Not for budget reasons, but for "deregulation is good" reasons. The money isn't gone. We've just got people who'd like "a government so small they can drown it in a bathtub". Well, it's drowning alright. [1] http://community.seattletimes.nwsource.com/archive/?date=19950604&slug=2124639#_ga=2.157427770.1261468268.1559139971-1010226798.1559139971 http://community.seattletimes.nwsource.com/archive/?date=199...
zubspace 7y ago
There's one thing I don't understand while looking at the flight recorder data: After flaps are retracted for the final time, the altitude seems to stabilize. So why the sudden drop before the crash? Why couldn't the pilots just keep on flying on the same level? There must be a sudden behavioural change of the plane or the pilots right before it went down, but I never got it explained to me clearly why... Second question: why did they retract the flaps? Wouldn't the wings generate more lift with flaps extended?
- ambicapter 7y ago
  > Wouldn't the wings generate more lift with flaps extended? Sure, until they get ripped off at speed. Flaps aren't a magic "more lift plz" button.
- tomglynch 7y ago
  IIRC, the pilot increased thrust to increase airspeed which made it harder to pull back on the yoke to fight against MCAS. I will need to check references again but I just got into bed. Edit: here we go: Pilots have demonstrated in simulator that the trim wheels cannot be moved in severe mis-trim conditions combined with a high airspeed.[92][93] As the pilots on Flight 302 pulled on the yoke to raise the nose, the aerodynamic forces on the tail’s elevator would create an opposing force on the stabilizer trim jackscrew that would prevent the pilots from moving the trim wheel by hand.[86][91][94] The resolution for this jammed trim issue is not part of Boeing's current 737 manual according to The Air Current.[90] The Seattle Times reports pilots on the 737-200 were trained for this failure, but latter models got so reliable, this procedure was no longer necessary.[91][90] Just stolen from Wikipedia before I sleep: https://en.m.wikipedia.org/wiki/Ethiopian_Airlines_Flight_302#Expert_analysis https://en.m.wikipedia.org/wiki/Ethiopian_Airlines_Flight_30...
  - dredmorbius 7y ago
    "Unable to trim": https://youtube.com/watch?v=aoNOVlxJmow https://youtube.com/watch?v=aoNOVlxJmow
- salawat 7y ago
wereHamster 7y ago
Don't airplanes have an equivalent of 'power steering' like we have in cars? It seems strange that pilots have to use actual physical force to move the control surfaces, and that there is a point where the physical force of a human is not enough anymore to move them. I get that Boeing wants to give pilots feedback of what is going on in and around the airplane. But putting pilots into a situation where they can't command the airplane even if they want to is a bit extreme.
- tomglynch 7y ago
  > putting pilots into a situation where they can't command the airplane even if they want to is a bit extreme. I agree, this is the main issue. In both cases if pilots had a clear option to just switch off MCAS we would have not lost over 500 lives.
  - gok 7y ago
    Unlikely. In the case of the first crash, they didn't even get as far as switching off the stab trim (they were flipping through the flight manual to find it as the plane crashed). A second switch would have done nothing if they couldn't remember how to use the first one. Yet another switch in a cockpit (which already has hundreds of them) would also have been yet another way to create an emergency by having a switch accidentally flipped the wrong way. In an emergency it has repeatedly been shown that pilots often forget complicated/rare recovery procedures. We need to stop relying on humans to perform at a superhuman level in these situations; better automation is the only way out.
    - infecto 7y ago
      Better automation like MCAS?
    - zubspace 7y ago
      On the other hand, there are many who believe, that automation got us into this. The more we automate, the more we depend on it which leads to problems if exceptional situations occur. [1] Maybe the 737 Max is just too complex and relies too much on automation to fly correctly? I'm reminded of the Quantas QF32 flight, where pilots were nearly overwhelmed by the endless amount of errors and checklists they had to perform. [2] [1] https://www.youtube.com/watch?v=lIusD6Z-3cU https://www.youtube.com/watch?v=lIusD6Z-3cU [2] https://www.news.com.au/travel/travel-advice/flights/inside-the-cockpit-on-qf32-how-the-worlds-worst-aviation-disaster-was-averted/news-story/62f3b73db38751b6ae0b3769058a48da https://www.news.com.au/travel/travel-advice/flights/inside-...
hughes 7y ago
Am I correct in understanding that the left angle-of-attack sensor was reading erroneously positive prior to takeoff?
- paulmd 7y ago
  I don't know whether that's true or not, but either way it doesn't matter. The AoA sensor does not function on the ground, it's basically a windvane and with no air moving over it, it would move to whatever angle gravity dictates.
  - ceejayoz 7y ago
    It should detectably not function, though, right? On level ground, with zero airspeed, it should always be in a certain position, and a deviation from that should be something the plane can detect and compensate for.
    - TomVDB 7y ago
      There could be a sufficient amount of friction in the system such that it could be in any position when the air speed is zero?
    - InternetOfStuff 7y ago
      Unless it's windy.
- deleted 7y ago
  [deleted]
- m463 7y ago
  A lot of aircraft systems key off of "weight on wheels" and other flags so they can ignore certain edge cases.
- FabHK 7y ago
  There are two complicating issues: A certain air speed is required (to turn the weather vane, as it were). While in ground effect, the air flow is different from the airflow in flight (away from the ground), so apparently a certain altitude above ground is required for the indication to be considered reliable. However, I believe that it should be possible to recognise a sufficiently defective AoA sensor during the take off roll, and possibly in time to abort the take off. However, not sure whether pilots are briefed to do so, as that is a risky manoeuvre in itself, and a missing AoA sensor should not be any problem per se (in the absence of MCAS that is trying to kill you).

Theodores 7y ago

> Also interesting to see is the amount of times the pilots bring the nose up, only for MCAS to kick in and force the nose back down. 26 times. That is awful. I heard that MCAS kicks in for ten seconds and then goes off for five seconds. So that must have been terrifying, for the pilot to think he has it under control for the death wish of MCAS to try again, and again and again until it gets its own way. When you look at how much has been invested in Homeland Security over the last seventeen years it is doubly tragic. It wasn't terrorists that we needed to fear, it was hasty management decisions at the FAA.

groby_b 7y ago
1) Let's place the blame where it belongs, Boeing. The FAA didn't force them to rely on a single sensor (in fact, given that MCAS can have hazardous consequences, two are mandatory IIRC). The FAA didn't force them to have MCAS three times the control range that's mentioned in the specs. The FAA didn't force them to not mention MCAS at all. 2) While this is certainly a tragic incident, it has nothing to do with homeland security existing or not. It's not like the autopilot suddenly decided to use planes as weapons. Apples and oranges.
- rdiddly 7y ago
  2) That is precisely the point though. We went crazy preventing apples when the threat was oranges.
  - Theodores 7y ago
    Thanks for that, the point has not been made in mainstream media, but time will reveal what a farce the Homeland Security thing was, a project fear to keep everyone believing what they have been believing. Meanwhile the FAA has been changed from being the helpful body it once was. Blaming Boeing is one thing but we know from our own coding work that you don't have the programmer test and deploy mission critical stuff, you get someone else to do it. It is a team effort. In code if you cut the people out that do all the testing and just ask the programmers to deploy stuff when they want to it goes wrong. I am not cutting Boeing slack in this, if you go back to the programmer analogy, you still get your code written to best practice before you put it anywhere near the testing and deployment people.
- iforgotpassword 7y ago
  1) then why didn't they force them to use input from both? Why give this shitty design green light? Why outsource parts of the certification process to Boeing, the same company who's plane is to be certified? Because of 2) obviously. All the money is gone. No budget for rigorous testing and validation of specs.
  - groby_b 7y ago
    Outsourcing of certification predates homeland security - see e.g. mid-90s reporting on the 777 certification[1]. In fact, the idea of outsourcing parts of the certification process started IIRC in the mid-1940s. What did happen past 2001 (but not due to budget pressures) is that the airline manufacturers got the authority to appoint their own designees, and were allowed to self-certify. Not for budget reasons, but for "deregulation is good" reasons. The money isn't gone. We've just got people who'd like "a government so small they can drown it in a bathtub". Well, it's drowning alright. [1] http://community.seattletimes.nwsource.com/archive/?date=19950604&slug=2124639#_ga=2.157427770.1261468268.1559139971-1010226798.1559139971 http://community.seattletimes.nwsource.com/archive/?date=199...

zubspace 7y ago

There's one thing I don't understand while looking at the flight recorder data: After flaps are retracted for the final time, the altitude seems to stabilize. So why the sudden drop before the crash? Why couldn't the pilots just keep on flying on the same level? There must be a sudden behavioural change of the plane or the pilots right before it went down, but I never got it explained to me clearly why... Second question: why did they retract the flaps? Wouldn't the wings generate more lift with flaps extended?

ambicapter 7y ago
> Wouldn't the wings generate more lift with flaps extended? Sure, until they get ripped off at speed. Flaps aren't a magic "more lift plz" button.
tomglynch 7y ago
IIRC, the pilot increased thrust to increase airspeed which made it harder to pull back on the yoke to fight against MCAS. I will need to check references again but I just got into bed. Edit: here we go: Pilots have demonstrated in simulator that the trim wheels cannot be moved in severe mis-trim conditions combined with a high airspeed.[92][93] As the pilots on Flight 302 pulled on the yoke to raise the nose, the aerodynamic forces on the tail’s elevator would create an opposing force on the stabilizer trim jackscrew that would prevent the pilots from moving the trim wheel by hand.[86][91][94] The resolution for this jammed trim issue is not part of Boeing's current 737 manual according to The Air Current.[90] The Seattle Times reports pilots on the 737-200 were trained for this failure, but latter models got so reliable, this procedure was no longer necessary.[91][90] Just stolen from Wikipedia before I sleep: https://en.m.wikipedia.org/wiki/Ethiopian_Airlines_Flight_302#Expert_analysis https://en.m.wikipedia.org/wiki/Ethiopian_Airlines_Flight_30...
- dredmorbius 7y ago
  "Unable to trim": https://youtube.com/watch?v=aoNOVlxJmow https://youtube.com/watch?v=aoNOVlxJmow
salawat 7y ago

wereHamster 7y ago

Don't airplanes have an equivalent of 'power steering' like we have in cars? It seems strange that pilots have to use actual physical force to move the control surfaces, and that there is a point where the physical force of a human is not enough anymore to move them. I get that Boeing wants to give pilots feedback of what is going on in and around the airplane. But putting pilots into a situation where they can't command the airplane even if they want to is a bit extreme.

tomglynch 7y ago
> putting pilots into a situation where they can't command the airplane even if they want to is a bit extreme. I agree, this is the main issue. In both cases if pilots had a clear option to just switch off MCAS we would have not lost over 500 lives.
- gok 7y ago
  Unlikely. In the case of the first crash, they didn't even get as far as switching off the stab trim (they were flipping through the flight manual to find it as the plane crashed). A second switch would have done nothing if they couldn't remember how to use the first one. Yet another switch in a cockpit (which already has hundreds of them) would also have been yet another way to create an emergency by having a switch accidentally flipped the wrong way. In an emergency it has repeatedly been shown that pilots often forget complicated/rare recovery procedures. We need to stop relying on humans to perform at a superhuman level in these situations; better automation is the only way out.
  - infecto 7y ago
    Better automation like MCAS?
  - zubspace 7y ago
    On the other hand, there are many who believe, that automation got us into this. The more we automate, the more we depend on it which leads to problems if exceptional situations occur. [1] Maybe the 737 Max is just too complex and relies too much on automation to fly correctly? I'm reminded of the Quantas QF32 flight, where pilots were nearly overwhelmed by the endless amount of errors and checklists they had to perform. [2] [1] https://www.youtube.com/watch?v=lIusD6Z-3cU https://www.youtube.com/watch?v=lIusD6Z-3cU [2] https://www.news.com.au/travel/travel-advice/flights/inside-the-cockpit-on-qf32-how-the-worlds-worst-aviation-disaster-was-averted/news-story/62f3b73db38751b6ae0b3769058a48da https://www.news.com.au/travel/travel-advice/flights/inside-...

hughes 7y ago

Am I correct in understanding that the left angle-of-attack sensor was reading erroneously positive prior to takeoff?

paulmd 7y ago
I don't know whether that's true or not, but either way it doesn't matter. The AoA sensor does not function on the ground, it's basically a windvane and with no air moving over it, it would move to whatever angle gravity dictates.
- ceejayoz 7y ago
  It should detectably not function, though, right? On level ground, with zero airspeed, it should always be in a certain position, and a deviation from that should be something the plane can detect and compensate for.
  - TomVDB 7y ago
    There could be a sufficient amount of friction in the system such that it could be in any position when the air speed is zero?
  - InternetOfStuff 7y ago
    Unless it's windy.
deleted 7y ago
[deleted]
m463 7y ago
A lot of aircraft systems key off of "weight on wheels" and other flags so they can ignore certain edge cases.
FabHK 7y ago
There are two complicating issues: A certain air speed is required (to turn the weather vane, as it were). While in ground effect, the air flow is different from the airflow in flight (away from the ground), so apparently a certain altitude above ground is required for the indication to be considered reliable. However, I believe that it should be possible to recognise a sufficiently defective AoA sensor during the take off roll, and possibly in time to abort the take off. However, not sure whether pilots are briefed to do so, as that is a risky manoeuvre in itself, and a missing AoA sensor should not be any problem per se (in the absence of MCAS that is trying to kill you).