7 ms·
I'm fairly certain that the characteristic "If this component malfunctions loss of life is one potential outcome" is a solid case for the component actually bei
by ajxs 8y ago
I'm fairly certain that the characteristic "If this component malfunctions loss of life is one potential outcome" is a solid case for the component actually being safety critical.
The pilots would never have needed to disable MCAS had it not malfunctioned in this manner.
I'm not sure what redundancy has to do with this, but clearly there was a failure in a safety-critical system.
- dsfyu404ed 8y ago>I'm fairly certain that the characteristic "If this component malfunctions loss of life is one potential outcome" is a solid case for the component actually being safety critical. The same thing can be said for literally tons of components on a plane. You can't have them all be redundant. At some point you have to pick and choose. A sensor for an obviously supplemental feature seems like a pretty obvious one to choose not to be redundant. >I'm not sure what redundancy has to do with this, I think the part in the GP comment where he/she state that "no matter the likelihood of failure, safety critical systems should always be redundant" has something to do with it.
- chrisseaton 8y ago> You can't have them all be redundant. Why not?
- gtirloni 8y agoThe usual, cost. But I wonder how much the redundant sensor costs for airlines to ditch it.
- cjbprime 8y agoEvery 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.
- gtirloni 8y agoI think you're right. I misread it. My point about cost still stands. "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-initial-problem-leading-to-lion-air-crash-11545739204 https://www.wsj.com/articles/maintenance-lapse-identified-as...
- RandomTisk 8y agoRedundant wings? Fuselage? Just 2 obvious examples, back to my armchair.
- comex 8y agoTrue, there are some parts which are both safety critical and fundamentally unable to be made redundant, at least not without drastically compromising the overall design. But that doesn’t justify leaving out redundancy in parts which are able. In any case, the actual regulations in play here would have required redundancy if the consequences of failure had been properly categorized: > [I]n normal flight, an activation of MCAS to the maximum assumed authority of 0.6 degrees was classified as only a “major failure,” meaning that it could cause physical distress to people on the plane, but not death. [..] > He said virtually all equipment on any commercial airplane, including the various sensors, is reliable enough to meet the “major failure” requirement, which is that the probability of a failure must be less than one in 100,000. Such systems are therefore typically allowed to rely on a single input sensor. > But when the consequences are assessed to be more severe, with a “hazardous failure” requirement demanding a more stringent probability of one in 10 million, then a system typically must have at least two separate input channels in case one goes wrong. https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ https://www.seattletimes.com/business/boeing-aerospace/faile...
- chrisseaton 8y agoThose are silly examples and clearly not what anyone meant in terms of components.
- tim333 8y agoAlso there is a kind of redundancy in the wings say by making the internal structure much stronger than generally needed. You can have a fracture in one part without the wings falling off.
- logfromblammo 8y ago