9 ms·

There are a myriad of issues that put the planes at risk, but I think that the fact that when the control system (MCAS) is engaged causes it to ignore feedback

by rjvehn 7y ago

There are a myriad of issues that put the planes at risk, but I think that the fact that when the control system (MCAS) is engaged causes it to ignore feedback is the biggest issue of all. "But with the MCAS activated, said Fehrm, those breakout switches wouldn’t work. MCAS assumes the yoke is already aggressively pulled back and won’t allow further pullback to counter its action, which is to hold the nose down. Fehrm’s analysis is confirmed in the instructions Boeing sent to pilots last weekend. The bulletin sent to American Airlines pilots emphasizes that pulling back the control column will not stop the action. Fehrm said that the Lion Air pilots would have trained on 737 simulators and would have learned over many years of experience that pulling back on the yoke stops any automatic tail maneuvers pushing the nose down." [0]. If you bought a new computer, how pissed off would you be if you lost data not because of a hard-drive failure, but because of a weird design decision of the 1 penny caps lock key? Imagine spending the time to setup a proper RAID system and losing everything because of a design decision in the keyboard. I mean if the media keeps reporting about the small stuff that's wrong, it's going to make people go "well planes are complex and things happen" and almost ignore the seriousness of a design decision that ignores user input. [0]: https://www.seattletimes.com/business/boeing-aerospace/faa-evaluates-a-potential-design-flaw-on-boeings-737-max-after-lion-air-crash/ https://www.seattletimes.com/business/boeing-aerospace/faa-e...

rossdavidh 7y ago
Of all the many problems of the Boeing 737Max situation, and there are several, for once I don't think the media reporting is one of the biggest. But, your basic point stands.
- iClaudiusX 7y ago
  The root problem is the culture at Boeing and the FAA has shifted from safety first to profit first. The investigative reporting from The Seattle Times[0] indicates that safety engineers were pressured to avoid delays to rush out a competitor to the A320. Furthermore, their safety analysis was based on flawed assumptions to meet an artificial constraint of not requiring pilot simulator training in order to appease the airlines they were selling to. Finally, the FAA is allowing industry to self-certify critical systems with lax oversight. It is easy to get lost in the technical details of why a particular catastrophe happens. The common throughline is a broken culture where deviance is normalized and those who speak out are ignored. It's the same story with Chernobyl, Fukushima, the El Faro, the USS Fitzgerald and USS John S. McCain, Air France 447, and now the 737 Max. [0] - https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the...
  - Aeolun 7y ago
    > The root problem is the culture at Boeing and the FAA has shifted from safety first to profit first. So the same problem that pervades society everywhere now? I’m not sure if that wasn’t the case before, but it feels to me that people previously wanted to make lots of money by building great products, and they’ve just left the ‘building great products’ part behind.
    - karl_schlagenfu 7y ago
      The difference is, most products aren't safety critical like aeroplanes.
    - mycall 7y ago
      That is exaggerated. It doesn't pervade everywhere.
    - shaki-dora 7y ago
      Despite the 737 Max fiasco, airplanes today are far safer than ever before. Since 1970, annual deaths have been cut by >80%, while air traffic has increased by a factor of 10. Cars have seen similar improvements. So have food hygiene, workplace safety, and most any measurable safety record I can think of.
      - simion314 7y ago
        You are using statistics wrong here, FAA process changed , Boeing entered a panic mode so their process changed too, applying statistics from the past where processes were different(FAA did its job and Boeing was no cutting corners) is incorrect. We need new statistics, and this are the stats for the recent Boeing plane where the MAX crashed 2 times, first crash was blamed on the pilots and no serious urgent investigation was performed, the MCAS issues that were discovered were trivialized, still Beoing is trying to shift t6he blame on a bad software and not on the actual causes . My point is that you can't use statistics that way, there are rules on how to apply them correctly and many pitfalls when applying statistics in real world scenarios.
th0ma5 7y ago
To be fair, ignoring user input could have potentially have saved Air France 447... I mean I actually can't think of an automated fool proof system that would've fixed 447, but incorrect input was a major factor.
- hannasanarion 7y ago
  The incorrect user input on AF447 happened AFTER all of the automatic systems had failed due to sensor clogging. How could ignoring user input have helped the flight when the plane's computer giving up was the cause of the manual takeover in the first place?
  - th0ma5 7y ago
    Yes, I guess that's where I say I don't know of a fool proof system, and then yeah how would it know it was incorrect input. I was simply saying incorrect input, given the actual situation, was an issue.
- cyberferret 7y ago
  Basic rudimentary 'stick and rudder' flying skills was a big factor in AF447's crash. All old school pilots know that when you aircraft is in a nose high stall condition, you never keep pulling back on the stick, but instead push it forwards to lower the nose and get the wings flying again. The fact that the co-pilot in question kept holding the stick to the back stops was the main reason that the aircraft wallowed into the sea. Weirdly, he did let go of the stick for a brief few seconds, which was the only time during the harrowing descent that the aircraft started to behave normally, but then he pulled it back and held it back right up until impact. Yep, the aircraft could have ignored these inputs, but the inputs are counter to what any reasonably skilled pilot would have done. (Note: Different to the MAX crashes where pulling back on the stick under speed IS the accepted way to stop a descent.)
  - jacquesgt 7y ago
    Part of the issue may have been that the plane had slowed down so much that the stall warning stopped (it disengages below a certain airspeed apparently). When he stopped pulling up, the plane sped up and the stall warning started again. Pull up again, plane slows down, stall warning stops.
yread 7y ago
It was designed to trim down when the pilot is pulling up. Of course pulling up is not going inhibit it. That's the point of the system!
pas 7y ago
The problem was that because it was an unknown component its failure mode was not known, which created/exacerbated the panic. There is a simple procedure, which is already part of the standard memory checklists. What to do in case of runaway trim. The pilots must/should be able to notice the trim wheels spinning, they then can disable trim motors and fall back to manually cranking them. The problem is, panic makes a mess of almost anybody. Sure, pilots shouldn't be anybody, but we know how much cost cutting has been going on.
- rtkwe 7y ago
  Well also the fact that the stabilizer can get trimmed far enough that the aerodynamic load on the rear stabilizer exceeds the pilots ability to move it manually. In that case the only real solution early in take off would be to re-enable the trim system so you could use the trim motors. The other solution to that situation is to nose down to release some of the pressure on the stabilizer so they can be manually cranked again, this isn't really an option early in the flight though because you don't have the altitude to slowly undo the erroneous trim while diving.
  - pas 7y ago
    I wasn't aware, and seemed quite ridiculous that there was not enough torque to rotate the screw, but looking at it, the angel of the helical threading is pretty steep. https://www.netairspace.com/photos/N37474/United_Airlines/Boeing_737-924ER/MCO_KMCO_Orlando_International_McCoy/photo_26571/ https://www.netairspace.com/photos/N37474/United_Airlines/Bo... And it turns out this can/happens even with the electronic motorized way, and there is a maneuver to work around the load. But it got removed from the manual... https://www.pprune.org/tech-log/619326-boeing-advice-aerodynamically-relieving-airloads-using-manual-stabilizer-trim.html#post10414805 https://www.pprune.org/tech-log/619326-boeing-advice-aerodyn...

by rjvehn 7y ago

rossdavidh 7y ago

Of all the many problems of the Boeing 737Max situation, and there are several, for once I don't think the media reporting is one of the biggest. But, your basic point stands.

iClaudiusX 7y ago
The root problem is the culture at Boeing and the FAA has shifted from safety first to profit first. The investigative reporting from The Seattle Times[0] indicates that safety engineers were pressured to avoid delays to rush out a competitor to the A320. Furthermore, their safety analysis was based on flawed assumptions to meet an artificial constraint of not requiring pilot simulator training in order to appease the airlines they were selling to. Finally, the FAA is allowing industry to self-certify critical systems with lax oversight. It is easy to get lost in the technical details of why a particular catastrophe happens. The common throughline is a broken culture where deviance is normalized and those who speak out are ignored. It's the same story with Chernobyl, Fukushima, the El Faro, the USS Fitzgerald and USS John S. McCain, Air France 447, and now the 737 Max. [0] - https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the...
- Aeolun 7y ago
  > The root problem is the culture at Boeing and the FAA has shifted from safety first to profit first. So the same problem that pervades society everywhere now? I’m not sure if that wasn’t the case before, but it feels to me that people previously wanted to make lots of money by building great products, and they’ve just left the ‘building great products’ part behind.
  - karl_schlagenfu 7y ago
    The difference is, most products aren't safety critical like aeroplanes.
  - mycall 7y ago
    That is exaggerated. It doesn't pervade everywhere.
  - shaki-dora 7y ago
    Despite the 737 Max fiasco, airplanes today are far safer than ever before. Since 1970, annual deaths have been cut by >80%, while air traffic has increased by a factor of 10. Cars have seen similar improvements. So have food hygiene, workplace safety, and most any measurable safety record I can think of.
    - simion314 7y ago
      You are using statistics wrong here, FAA process changed , Boeing entered a panic mode so their process changed too, applying statistics from the past where processes were different(FAA did its job and Boeing was no cutting corners) is incorrect. We need new statistics, and this are the stats for the recent Boeing plane where the MAX crashed 2 times, first crash was blamed on the pilots and no serious urgent investigation was performed, the MCAS issues that were discovered were trivialized, still Beoing is trying to shift t6he blame on a bad software and not on the actual causes . My point is that you can't use statistics that way, there are rules on how to apply them correctly and many pitfalls when applying statistics in real world scenarios.

th0ma5 7y ago

To be fair, ignoring user input could have potentially have saved Air France 447... I mean I actually can't think of an automated fool proof system that would've fixed 447, but incorrect input was a major factor.

hannasanarion 7y ago
The incorrect user input on AF447 happened AFTER all of the automatic systems had failed due to sensor clogging. How could ignoring user input have helped the flight when the plane's computer giving up was the cause of the manual takeover in the first place?
- th0ma5 7y ago
  Yes, I guess that's where I say I don't know of a fool proof system, and then yeah how would it know it was incorrect input. I was simply saying incorrect input, given the actual situation, was an issue.
cyberferret 7y ago
Basic rudimentary 'stick and rudder' flying skills was a big factor in AF447's crash. All old school pilots know that when you aircraft is in a nose high stall condition, you never keep pulling back on the stick, but instead push it forwards to lower the nose and get the wings flying again. The fact that the co-pilot in question kept holding the stick to the back stops was the main reason that the aircraft wallowed into the sea. Weirdly, he did let go of the stick for a brief few seconds, which was the only time during the harrowing descent that the aircraft started to behave normally, but then he pulled it back and held it back right up until impact. Yep, the aircraft could have ignored these inputs, but the inputs are counter to what any reasonably skilled pilot would have done. (Note: Different to the MAX crashes where pulling back on the stick under speed IS the accepted way to stop a descent.)
- jacquesgt 7y ago
  Part of the issue may have been that the plane had slowed down so much that the stall warning stopped (it disengages below a certain airspeed apparently). When he stopped pulling up, the plane sped up and the stall warning started again. Pull up again, plane slows down, stall warning stops.

yread 7y ago

It was designed to trim down when the pilot is pulling up. Of course pulling up is not going inhibit it. That's the point of the system!

pas 7y ago

The problem was that because it was an unknown component its failure mode was not known, which created/exacerbated the panic. There is a simple procedure, which is already part of the standard memory checklists. What to do in case of runaway trim. The pilots must/should be able to notice the trim wheels spinning, they then can disable trim motors and fall back to manually cranking them. The problem is, panic makes a mess of almost anybody. Sure, pilots shouldn't be anybody, but we know how much cost cutting has been going on.

rtkwe 7y ago
Well also the fact that the stabilizer can get trimmed far enough that the aerodynamic load on the rear stabilizer exceeds the pilots ability to move it manually. In that case the only real solution early in take off would be to re-enable the trim system so you could use the trim motors. The other solution to that situation is to nose down to release some of the pressure on the stabilizer so they can be manually cranked again, this isn't really an option early in the flight though because you don't have the altitude to slowly undo the erroneous trim while diving.
- pas 7y ago
  I wasn't aware, and seemed quite ridiculous that there was not enough torque to rotate the screw, but looking at it, the angel of the helical threading is pretty steep. https://www.netairspace.com/photos/N37474/United_Airlines/Boeing_737-924ER/MCO_KMCO_Orlando_International_McCoy/photo_26571/ https://www.netairspace.com/photos/N37474/United_Airlines/Bo... And it turns out this can/happens even with the electronic motorized way, and there is a maneuver to work around the load. But it got removed from the manual... https://www.pprune.org/tech-log/619326-boeing-advice-aerodynamically-relieving-airloads-using-manual-stabilizer-trim.html#post10414805 https://www.pprune.org/tech-log/619326-boeing-advice-aerodyn...