Bit more of a technical description here. Love the vernacular use in the first part. It would be useful to know how the pilots/simulator recovered e.g. did they just wait for the processor to sort itself out or was there some reset performed?
'It's understood the code that knackered the hardware was part of a firmware update to address deadly flaws in MCAS, the 737 Max's anti-stall tech that wound up killing hundreds of people.
To us, it sounds as though code in the MCAS update either forces the processor into a locked state, such as a tight unbreakable and uninterruptable infinite loop, or triggers an exception that can't be handled and the CPU halts. It is remotely possible the code encounters a design flaw in the unidentified microprocessor that causes the circuitry to freeze.'https://www.theregister.co.uk/2019/06/2 ... bug_found/
The Guardian article seems to say very different things than the CNN article which the Guardian article seems to be using as the source. The CNN article seems to indicate that a scenario was tested based on FAA input to determine what would happen IF
a microprocessor failed. The result was that if there was a failure it could result in uncommanded nose down trim. The article then states that Boeing engineers are evaluating how to mitigate the risk. Nowhere does the CNN article state or imply that the software locked up a microprocessor.
On the other hand, the Guardian article says that the software "would lock up a microprocessor." It does not pass the common sense test that this didn't happen in weeks of Boeing internal testing or that it did happen and they just let the FAA evaluate it anyway. The Guardian then states the following:
The US manufacturer on Wednesday confirmed that, during simulator tests on the embattled jetliners, the 737 Max's new control software would lock up a microprocessor resulting in the plane automatically entering a dangerous nosedive.
There is no supporting quote for this statement. By saying the US manufacurer "confirmed" indicates an official statement, not an anonymous source. The offical statement from Boeing is:
The safety of our airplanes is Boeing’s highest priority. During the FAA’s review of the 737 MAX software update and recent simulator sessions, the Federal Aviation Administration (FAA) identified an additional requirement that it has asked the company to address through the software changes that the company has been developing for the past eight months. The FAA review and process for returning the 737 MAX to passenger service are designed to result in a thorough and comprehensive assessment. Boeing agrees with the FAA's decision and request, and is working on the required software. Addressing this condition will reduce pilot workload by accounting for a potential source of uncommanded stabilizer motion. Boeing will not offer the 737 MAX for certification by the FAA until we have satisfied all requirements for certification of the MAX and its safe return to service.
Where does that remotely confirm that the "new control software would lock up a microprocessor?" The fact that the official statement says "accounting for a potential source of uncommanded stabilizer motion" makes it line up with the CNN reporting that the FAA identified a potential cause of runaway stabilizer.
My bigger concern is whether this potential cause exists on the NG as well. Since MCAS appears to be an extension of the STS code, is the same microprocessor and interface design used on the NG and can it cause a runaway stabilizer? If yes, is this just a case of the FAA being overly cautious about the MAX and making sure to cover every possible cause of runaway stabilzier even if it is exceedingly rare or unlikely?
I would put the brakes on drawing conclusions based on the Guardian article. It looks to me like they took the CNN article and embelished it for drama and clicks but may have created some "fake news" on top of the real facts reported by CNN.