Reply to post: Re: Hey software, get the fuck out of the way!

Boeing 737 pilots battled confused safety system that plunged aircraft to their deaths – black box

Remy Redert

Re: Hey software, get the fuck out of the way!

That was an Airbus and the software reacted correctly. It decided that the airspeed information it was getting from the various sensors was conflicting, so it switched from normal law (where it controls the airplane and the pilots are allowed to tell it where to go) to alternate law 2 (aka "I don't know any more, you're up pilots").

The pilots then proceeded to over-correct for a slight roll caused by the autopilot switching off, pulled the nose up, got a brief stall warning when the angle of attack sensors indicated something was up and then proceeded to put the plane into a stall so deep the computer considered the measurements of the alpha sensors to be impossible, so it did nothing and assumed the pilots were doing the right thing.

The software (and software designers) in this case did everything right and the pilots proceeded to crash the plane. Had the system switched back to normal law when the airspeed readings came back (about a minute after the failure, but before the stall), the airplane would never have stalled. But because of safety reasons, the pilots would have had to switch the plane back into normal mode themselves once they verified the problem that triggered the switch had been resolved.

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