201–210 of 269 posts
Is it possible for Boeing engineers to lose their professional status as a result of this situation?
Are you outside the US? Engineers here do not typically have professional status.
I can only think of one CEng I know, and he works in civil engineering. I've never met a Chartered/Certified software or electronics engineer (that I know of).
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US pilots say they didn't either. The training wasn't out there.
The runaway stabilizer trim procedure is how it was expected to be handled: https://www.flightglobal.com/news/articles/faa-order-tells-h... https://www.youtube.com/watch?v=3pPRuFHR1co The specifics of MCAS weren't out there because Boeing expected the pre-existing procedure to have been sufficient. That procedure wasn't sufficient, or the Lion and Ethiopian Air pilots were somehow not aware of it, or they forgot thei…
This was argued by Boeing to the FAA, who accepted the reasoning.
It should be noted that, if it had been determined the pre-existing procedure wasn't sufficient, then all pilots on the 737 Max would've had to undergo re-training. This would have been expensive, and probably hurt adoption of the new airframe.
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The usual, cost. But I wonder how much the redundant sensor costs for airlines to ditch it.
Every 737 has two AoA vanes. They are redundant and the redundancy is not optional. MCAS just doesn't take advantage of there being two sensors.
"Cockpit displays and a warning light intended to flag problems with angle-of-attack sensors in flight were optional on the Lion Air jet that crashed, according to people familiar with the matter. The carrier, like some others, chose not to purchase the feature, people familiar with the matter said, so pilots didn’t receive any such alerts."
https://www.wsj.com/articles/maintenance-lapse-identified-as...
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I've flown on a 737 MAX a couple times this year. Smooth, comfortable, quiet flight. Although the failure of the MCAS system has been catastrophic, fortunately for Boeing the fix doesn't seem difficult... make an extra AoA vane or two mandatory and add a warning if they disagree, and require MAX pilots to sim train an MCAS failure. The planes seem eminently airworthy, so far it appears they weren't brought down by an…
There's already two AoA vanes mandatory on every plane (even non-MAX planes). There is a warning if they disagree in the optional package that the North American airlines bought, but not any other airlines. The warning is not much of a warning, just a disagree light. It would have been impossible for the Lion Air pilots to benefit from this disagree light, because they didn't know that it was hooked up to a control s…
And all Airbus types have three or four. Boeings only have two, even on the 787 ( on which one is vulnerable to damage from jetbridges ).
It is disappointing that a manufacturer would cut corners on sensors for a $100 million aircraft.
> [T]hey got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit. That extra pilot, who was seated in the cockpit jumpseat [...] Am I missing something here? Isn't it normal for off-duty pilots to ride in the jump-seat?
Absolutely not, I know several airline pilots and they deadhead in economy seats.
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The runaway stabilizer trim procedure is how it was expected to be handled: https://www.flightglobal.com/news/articles/faa-order-tells-h... https://www.youtube.com/watch?v=3pPRuFHR1co The specifics of MCAS weren't out there because Boeing expected the pre-existing procedure to have been sufficient. That procedure wasn't sufficient, or the Lion and Ethiopian Air pilots were somehow not aware of it, or they forgot thei…
One thing I've been wondering: somehow the pilots were able to bring the nose back up... it was only (apparently) after multiple nose downs that they eventually failed to recover the plane. What was going on there? It's as if they understood how to correct the stabilizer trim, but weren't aware of the cut-off switches. My understanding is that every time the MCAS activated, its effect was incremental. It could comman…
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This is grossly overstating the optional feature. As I understand it, "AOA disagree" is a single light near the AoA indicator itself. It's not an explanation, or even an alert. It's not where anyone would reasonably look when trying to diagnose an uncommanded flight control problem.
When lights are normally not lit and one lights up a pilot or other machine or plant operator should take notice. A detailed explanation should not be required since they should know what the different warning lights mean and what can cause them to be lit. I personally would like to see a list of the airlines that bought the more expensive 737 max that included the additional safety features.
The crew monitor the central EICAS display for fault indications, not random locations around the cockpit.
If you start bolting-on additional check locations you increase crew workload, particularly if it's not a 'dark cockpit' like an Airbus type.
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Could be related to the issue that MAX is unstable in flight with that system off. Unlike previous 737s.
No, under normal conditions the MAX isn't unstable. The instability comes only at high angles of attack (close to stalling) and only there the MCAS system should kick in. It was meant to be the equivalent to ESP systems in cars.
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Could be related to the issue that MAX is unstable in flight with that system off. Unlike previous 737s.
No, under normal conditions the MAX isn't unstable. The instability comes only at high angles of attack (close to stalling) and only there the MCAS system should kick in. It was meant to be the equivalent to ESP systems in cars.
The saddest thing, as many HN users should know all to well, is that there can be no excuse for automated systems like airliners to experience catastrophic failure and loss of life, if only due to the availability and application of modern SDLC principles and CI/CD etc. Smoke testing could have been performed such that all possible combinations of transducer input could be considered and evaluated thoroughly for clos…
Speaking as someone who's done this (though not on a something as big as an airliner!) Yes, you can test control loops -- you can even turn it into a unit test. At least in theory. The problem is that to do the test you need either a working, physical system or a good model. So if you're making a shutdown valve for a chemical plant, you need a physical build of that control valve. Even on that scale, you're talking a…
Even with the best modeling and virtualization, a true and thorough, 100% 1:1 approximation with the real world at runtime can likely never be attained for a myriad of reasons.
However, when lives are on the line, this gap must be closed in some manner so as to provide a greater degree of confidence.
Even the most thirsty organizations with lesser consequences for their failures are usually conservative enough and risk-averse enough to know better than to release without thorough (and relatively inexpensive) testing.
My old boss used to tell stories about back in the mainframe days whereby he would send customers fancy, branded and shrink-wrapped finished-product but containing blank tapes for the latest release in order to buy a couple of weeks of extra dev time if he thought the software wasn't ready to escape.