4 ms·

Redundant wings? Fuselage? Just 2 obvious examples, back to my armchair.

comex 8y ago
True, 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 ago
Those are silly examples and clearly not what anyone meant in terms of components.
- tim333 8y ago
  Also 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
    There is also much more wing than is strictly needed to keep the plane aloft and stable. They're optimized for low fuel consumption at a design-specified cruising altitude and speed, with variable geometry, so they can still take off and land at lower speeds near ground level. From a certain perspective, the flaps give the plane redundant wings. One pair for low and slow, and another pair for high and fast.

True, 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 ago

Those are silly examples and clearly not what anyone meant in terms of components.

tim333 8y ago
Also 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
  There is also much more wing than is strictly needed to keep the plane aloft and stable. They're optimized for low fuel consumption at a design-specified cruising altitude and speed, with variable geometry, so they can still take off and land at lower speeds near ground level. From a certain perspective, the flaps give the plane redundant wings. One pair for low and slow, and another pair for high and fast.