How Boeing, FAA certified the suspect 737 MAX flight control system
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Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#2Required reading for anyone interested in understanding what probably went wrong.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#3So this is the equivalence of “let the software engineers do the QA” thing.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#4This is a pretty damning statement, with respect to the original safety analysis submitted to the FAA:
"The safety analysis... assessed a failure of the system as one level below “catastrophic.” But even that “hazardous” danger level should have precluded activation of the system based on input from a single sensor — and yet that’s how it was designed."
Neither Boeing nor the FAA should have given this a pass.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#5The FAA, citing lack of funding and resources, has over the years delegated increasing authority to Boeing to take on more of the work of certifying the safety of its own airplanes.
How does it work in other countries?
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#6The FAA, citing lack of funding and resources, has over the years delegated increasing authority to Boeing to take on more of the work of certifying the safety of its own airplanes. How does it work in other countries?
Many countries effectively delegate it to the FAA.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#7"Both Boeing and the FAA were informed of the specifics of this story and were asked for responses 11 days ago, before the second crash of a 737 MAX last Sunday."
i.e. people were following up on this before the public outcry started.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#8For those who were wondering why pilots didn't override the autopilot? Turns out that just made things worse:
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The discrepancy over this number is magnified by another element in the System Safety Analysis: The limit of the system’s authority to move the tail applies each time MCAS is triggered. And it can be triggered multiple times, as it was on the Lion Air flight.
One current FAA safety engineer said that every time the pilots on the Lion Air flight reset the switches on their control columns to pull the nose back up, MCAS would have kicked in again and “allowed new increments of 2.5 degrees.”
“So once they pushed a couple of times, they were at full stop,” meaning at the full extent of the tail swivel, he said.
Peter Lemme, a former Boeing flight controls engineer who is now an avionics and satellite-communications consultant, said that because MCAS reset each time it was used, “it effectively has unlimited authority.”
...
Boeing insists that the pilots on the Lion Air flight should have recognized that the horizontal stabilizer was moving uncommanded, and should have responded with a standard pilot checklist procedure to handle what’s called “stabilizer runaway.”
If they’d done so, the pilots would have hit cutoff switches and deactivated the automatic stabilizer movement.
Boeing has pointed out that the pilots flying the same plane on the day before the crash experienced similar behavior to Flight 610 and did exactly that: They threw the stabilizer cutoff switches, regained control and continued with the rest of the flight.
However, pilots and aviation experts say that what happened on the Lion Air flight doesn’t look like a standard stabilizer runaway, because that is defined as continuous uncommanded movement of the tail.
On the accident flight, the tail movement wasn’t continuous; the pilots were able to counter the nose-down movement multiple times.
In addition, the MCAS altered the control column response to the stabilizer movement. Pulling back on the column normally interrupts any stabilizer nose-down movement, but with MCAS operating that control column function was disabled.
These differences certainly could have confused the Lion Air pilots as to what was going on.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#9So this is the equivalence of “let the software engineers do the QA” thing.
Nope, software engineers at least have a sense of proper QA.
This is the equivalence of “let the product manager do the QA” thing.
Re: How Boeing, FAA certified the suspect 737 MAX flight control system
#10Notable and disturbing here is the lack of Max simulators in existence. It looks like neither Lion Air nor Ethiopian nor any US airline had access to one.
Also linked in this article is the original FAA table of differences between the Max and other 737 models. It makes no metion of MCAS.