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And after the Ethiopian crash I won't be getting on a 737max8 until I see the fix for these crashes. EASA did exactly the right thing, ground first, prove it later. FAA and Boeing reacted way too slowly. You can't argue everything is fine when 300 people have died. THREE. HUNDRED.
*An Official Foo-Approved guitarist since Sept 2023.
I actually think that if the cause of both crashes is indeed found to be faults in the way MCAS works, a hard look will have to be taken by the regulators at ‘grandfathering’ of old designs. Essentially Boeing has taken the 737 so far beyond its original form that it becomes unstable under certain circumstances and needs a software fix for that, but the software can then make things worse if it gets faulty data. That’s not an inherently safe system.
This does seem to be the first time since the 1960s - actually since before the original 737 was introduced - that a new aircraft appears to be less safe than its predecessor. Ironically the problem is that the number of incidents is so small that it’s hard to be sure yet, but that alone shows how rigorous the industry has been in prioritising safety - and they need to continue to take the awkward path of possibly excessive caution which has got us there.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I always presumed there’d be at least one redundancy system in the case of a faulty sensor, but it doesn’t look to be the case. Unless I’ve misread it, a system where the software polls all the other sensors to see if they agree with the faulty one is “an optional extra”??!! Madness.
Making anything like that an optional cost item reminds me of some early calculators which had some features deliberately crippled in order to market an apparently different model at a lower price point.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
IIRC the big problem with MCAS (other than the obvious single sensor reliance), is it doesn't disable when the pilots think it has, so the pilots end up continually fighting it, and think there's some other problem they need to handle, when in fact it's just the MCAS continually cutting in.
Also, Boeing provide all the tools and training, it’s up to the airlines to get the relevant people trained up.
The MCAS system while aiming to improve safety, in this case wasn't tested thoroughly enough and appears to be faulty.
The are multiple issues and some of them may or may not be true.
The pilots apparently didn't know how to disable MCAS because the shutdown mechanism had changed.
It is possible that the sensors were damaged or gave incorrect readings due to external factors, possibly a fire.
MCAS appears to have no real redundancy or an automatic shut off in the case of suspected incorrect readings.
The issue of safety has always been present in all automation and a large focus of recent Computer Science research is how to make AI safe and explainable.
On newer systems, each PLC had it's own set of sensors, so any sensor failure would be detected and deactivate the entire system.
To save money on retrofitted systems, somebody decided the PLCs should share some of the same sensors, as it was deemed too expensive to fit the duplicate sensors, and the shared sensors would never fail in such a way as to cause a full system activation.
I'm sure you can guess what happened.