FFS -- Boeing finds *another* 737 MAX software problem

[Recursion]

https://www.theverge.com/2020/2/6/21126364/boeing-737-max-software-glitch-flaw-problem

Emphasis mine:

Boeing has discovered another software problem on the beleaguered 737 Max that will have to be fixed before the airplane returns to the skies, Bloomberg reported on Thursday. It’s at least the third different software problem that has been discovered since the plane was grounded in March of last year following a pair of fatal crashes that claimed the lives of 346 people.

The new issue apparently has to do with a warning light that helps tell pilots when the trim system — a part of the plane that can lift or lower the nose — isn’t working. Federal Aviation Administration head Steve Dickson said during a talk in London on Thursday that the light was “staying on for longer than a desired period,” according to Bloomberg.

Boeing and the FAA have previously disclosed two other glitches that were discovered during the top-to-bottom review of the plane. In January, Boeing announced that it found a problem in the startup process of the plane’s flight computers, which was serious enough for the company and the FAA to delay a key test flight. That followed a previous flaw in the flight computer discovered last June that the FAA said “could cause the plane to dive in a way that pilots had difficulty recovering from in simulator tests.”

What’s worrisome about this new glitch is that it’s a direct result of the fixes Boeing made to those previous flaws, Boeing said Thursday. The trim system flaw “resulted from Boeing’s redesign the two flight computers that control the 737 Max to make them more resilient to failure,” Bloomberg reported, which Boeing later confirmed. The new glitch is also more directly related to a system that was involved in the original problem with the 737 Max.

[MontanaMama]

1. Why'd Boeing have to screw with the 737 at all?

Workhorse of passenger aviation for decades.

[Recursion]

3. The idea was to redesign the 737 to use the same supply chain as the 787

On paper it sounds great, in practice...

[Dennis Donovan]

2. Not unusual for new programming to trip up older code. I'm not sure this is a problem

Sounds like, overall, they're working thru the problem.

[Recursion]

4. The best way to fix a regression is to never introduce it (nt)

[WyattKansas]

5. Haven't any of them ever thought it was a bad idea to...

Treat an airplane like a computer that can be updated and fixed after it's release?

[Midnightwalk]

6. Some more

First I’m not defending Boeing at all. I have a strange fascination for computer bugs. I also have no knowledge of aviation computer systems or aviation systems in general. So don’t trust what I’m saying.

The failure in June that caused a major redesign was that apparently the system couldn’t handle a processor failure.

In simulator tests, government pilots discovered that a microprocessor failure could push the nose of the plane toward the ground. It is not known whether the microprocessor played a role in either crash.

When testing the potential failure of the microprocessor in the simulators, "it was difficult for the test pilots to recover in a matter of seconds," one of the sources said. "And if you can't recover in a matter of seconds, that's an unreasonable risk."

[link:https://amp.cnn.com/cnn/2019/06/26/politics/boeing-737-max-flaw/index.html|]

At the time I speculated the system couldn’t keep up with the reading both sensors. Maybe it was more like they couldn’t switch to the other processor fast enough. They must have had some redundancy built in, right? But it’s easy to speculate reasons, particularly without enough details.

In any case whatever the issue really was apparently caused some large sounding design changes.

The outcome of that simulated flight, a decision to redesign the 737 Max's flight-computer architecture, led to extensive delays that have dragged on through the summer and fall and now threaten Boeing's ability to deliver aircraft, book new orders, and maintain revenue expectations.

[link:https://www.businessinsider.com/boeing-737-max-flight-computer-redesign-delay-simulator-2019-11?amp|]

The current failure is a trim warning light stayed on too long. I have zero expertise in aviation and can’t say how severe a failure this is.

The problem isn’t necessarily just that warning light staying on too long. Maybe there’s even a simple fix for that. The problems are they missed something to catch it so late in the process. Is this problem indicative of a more pervasive problem? Maybe, maybe not.

At this point even a simple fix is going to require significant retest which can and should take quite a while. Particularly with all the problems they’ve had.

[abqtommy]

7. Boeing needs to stop hiring those tRUMP U. grads for their engineering staff!

[nitpicker]

8. Link to DW

https://www.dw.com/en/boeing-finds-new-flaw-on-grounded-737-max-jet/a-52285506