4 ms·

Relevant comment from yesterday: https://news.ycombinator.com/item?id=22101953 https://news.ycombinator.com/item?id=22101953 "Even a fix now proposed for the M

by tda 7y ago

Relevant comment from yesterday: https://news.ycombinator.com/item?id=22101953 https://news.ycombinator.com/item?id=22101953 "Even a fix now proposed for the Max has similarities with the past: After the crash near Amsterdam, the F.A.A. required airlines to install a software update for the NG that compared data from the plane’s two sensors, rather than relying on just one. The software change Boeing has developed for the Max also compares data from two sensors. Critically, in the case of the NG, Boeing had already developed the software fix well before the Turkish Airlines crash, including it on new planes starting in 2006 and offering it as an optional update on hundreds of other aircraft. But for some older jets, including the one that crashed near Amsterdam, the update wouldn’t work, and Boeing did not develop a compatible version until after the accident."

ShamelessC 7y ago
I don't know anything at all about aviation, but if redundancy of sensors is so crucial to these systems then why don't they have like 10 of them on there just in case? Are they particularly expensive? Do they need to be in certain locations on the plane to work properly? I'm obviously thinking about this from a software point of view where redundancy is cheap but I am curious if it's just greedy cost cutting or if there are legitimate reasons for this stuff.
- Gwypaas 7y ago
  Well, it is more expensive to have more than one. New fly by wire aircraft usually have 3 separate systems (sensors, computers and so on) voting to know which part fails and continue on working, or if everything fails do it to a safe-state. The protections are gone but you can fly the plane with direct inputs. Compare this to the ancient 737 where instead of the airplane detecting errors the pilots are supposed to do it by cross checking two flight computers. Thus we see now after the crashes Boeing forced to implement cross checking in a system not designed for it because things reliant on a single sensor has ended up being classified as safety critical.
- Anarch157a 7y ago
  Because that would add several million dollars to the airplane's price. An angle of attack sensor (the sensor MCAS relies on) for a small, twin-engine private jet can cost nearly $50,000. The ones in the MAX cost a lot more. Even if cost wasn't an issue, space and weight are. There are just so much stuff you can tackle on the fuselage or inside the engine cowling before it starts affecting the airplanes ability to fly.
- bumby 7y ago
  Flight material quality assurance is very expensive. It's not necessarily that the part itself is wildly expensive to manufacture, but the testing and traceability all need to done and maintained. It's adds quite a bit to the overall price tag. In other words, you can't just order from a catalog and install it. You need to order from a vetted supplier, who maintains testing and documentation, and can prove that it meets spec and also that all the materials used to make it meet spec. Then it has to be installed by a certified A&P mechanic etc. There's a long chain of events for something that seems relatively simple, but that's also why airlines are about the closest thing to a truly six-sigma organization.

by tda 7y ago

ShamelessC 7y ago

I don't know anything at all about aviation, but if redundancy of sensors is so crucial to these systems then why don't they have like 10 of them on there just in case? Are they particularly expensive? Do they need to be in certain locations on the plane to work properly? I'm obviously thinking about this from a software point of view where redundancy is cheap but I am curious if it's just greedy cost cutting or if there are legitimate reasons for this stuff.

Gwypaas 7y ago
Well, it is more expensive to have more than one. New fly by wire aircraft usually have 3 separate systems (sensors, computers and so on) voting to know which part fails and continue on working, or if everything fails do it to a safe-state. The protections are gone but you can fly the plane with direct inputs. Compare this to the ancient 737 where instead of the airplane detecting errors the pilots are supposed to do it by cross checking two flight computers. Thus we see now after the crashes Boeing forced to implement cross checking in a system not designed for it because things reliant on a single sensor has ended up being classified as safety critical.
Anarch157a 7y ago
Because that would add several million dollars to the airplane's price. An angle of attack sensor (the sensor MCAS relies on) for a small, twin-engine private jet can cost nearly $50,000. The ones in the MAX cost a lot more. Even if cost wasn't an issue, space and weight are. There are just so much stuff you can tackle on the fuselage or inside the engine cowling before it starts affecting the airplanes ability to fly.
bumby 7y ago
Flight material quality assurance is very expensive. It's not necessarily that the part itself is wildly expensive to manufacture, but the testing and traceability all need to done and maintained. It's adds quite a bit to the overall price tag. In other words, you can't just order from a catalog and install it. You need to order from a vetted supplier, who maintains testing and documentation, and can prove that it meets spec and also that all the materials used to make it meet spec. Then it has to be installed by a certified A&P mechanic etc. There's a long chain of events for something that seems relatively simple, but that's also why airlines are about the closest thing to a truly six-sigma organization.