Software Won’t Fix Boeing’s ‘Faulty’ Airframe

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by inferiorhuman on Thursday March 28, 2019 @02:46AM (#19509840)

MCAS operates on the horizontal stabilizer (and is not a stick pusher like the article claims) the yoke operates on the elevators. The elevators are much smaller and lack the pitch authority of the stabilizer. The stabilizer moves much slower and by the time you've stalled under the conditions MCAS is designed to prevent, you may not have time for the stabilizer to move.

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by manfredo on Thursday March 28, 2019 @02:55AM (#19509887)

> MCAS operates on the horizontal stabilizer (and is not a stick pusher like the article claims) the yoke operates on the elevators.

https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi...

So the issue is that MCAS was controlling the big control surfaces, the pilots' attempts to correct with yoke input operated on the small control surfaces? The former overpowered the latter.

Interesting that MCAS wasn't like cruise control where any significant input deactivates the automated controls. But then again, I know next to nothing about how big airliner control systems work.

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by azernik on Thursday March 28, 2019 @03:09AM (#19509946)

> Interesting that MCAS wasn't like cruise control where any significant input deactivates the automated controls.

It would disengage... but then would immediately re-engage if the bad sensor readings were still there. And would, in the meanwhile, have reset its control limiter so it would push even harder than the first time.

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by concerned_user on Thursday March 28, 2019 @03:47AM (#19510163)

Also thanks to "zero training delta" commitment pilots probably didn't even know it exists or in a high-stress situation like imminent stall probably just forgot about it all.

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by acqq on Thursday March 28, 2019 @05:05AM (#19510487)

It's worse: the pilots are supposed to "jump in" instead of the software when the plane is typically already in the critical state and then to control the plane which behaves exactly differently from the way they are trained. Only when the MCAS operates "properly" the plane behaves as they were trained!

That "omission" was intentional as the Boeing selling point was "it is the same old, no new pilot training needed." That's how they have "sold" the worth of 600 billion dollars of the MAX planes!

The probable strategy for Boeing was "we will blame the pilots" and had the two crashes not happened so fast one after another they would have probably got away with it!

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by inferiorhuman on Thursday March 28, 2019 @07:26AM (#19511089)

They're supposed to jump in and resolve the problem within forty seconds apparently. Otherwise they're screwed[1].

Those involved in the testing hadn’t fully understood just how powerful the system was until they flew the plane on a 737 Max simulator, according to the two people.

1: https://www.nytimes.com/2019/03/25/business/boeing-simulatio...

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by ams6110 on Thursday March 28, 2019 @11:10AM (#19512928)

The 40 seconds is misleading. The MCAS system could in the worst case run the trim full nose down in 40 seconds (it's active for 10 seconds with a 5 second delay between cycles) if the pilot does nothing to counter it.

It's like if you are driving and the road starts to curve. If you do nothing, yes you will get to a point where a crash is unavoidable. But you know that when your car is not following the road, you turn the steering wheel. Pilots know that when they have to pull the yoke to keep the plane level, they need to trim.

[ Parent | on HN ]

Re:Software Won’t Fix Boeing’s ‘Faulty’ Airframe by azernik on Thursday March 28, 2019 @07:21PM (#19517628)

The problem is that if you do the intuitive thing (which is what pilots are trained to do for most trim overruns - pull on the stick to counter the trim), the MCAS goes through the increasing cycle to full nose-down. It's 40 seconds to realize that your usual strategy isn't working, figure out what to actually do, and then turn off the exact right system.

[ Parent | on HN ]