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Long Uptime Makes Boeing 787 Lose Electrical Power
jones_supa writes: A dangerous software glitch has been found in the Boeing 787 Dreamliner. If the plane is left turned on for 248 days, it will enter a failsafe mode that will lead to the plane losing all of its power, according to a new directive from the US Federal Aviation Administration. If the bug is triggered, all the Generator Control Units will shut off, leaving the plane without power, and the control of the plane will be lost. Boeing is working on a software upgrade that will address the problems, the FAA says. The company is said to have found the problem during laboratory testing of the plane, and thankfully there are no reports of it being triggered on the field.
I guess this might be due to a 32-bit signed integer being incremented at 100 Hz: 2^31 / 24 / 3600 / 100 = 248.5 days.
karma police: arrest this man, he talks in maths; he buzzes like a fridge, he's like a detuned radio. [radiohead]
A commercial plane will most probably undergo through several maintenance events and checks during that sort of time frame, where cycling the power is part of the procedure.
It's very reassuring to know that it probably won't happen.
Actually I took my work there testing the 777 software very seriously.
On at least two occasions I escalated what I thought was a problem in the specification all the way back to Boeing. One of them turned out to be a "real-world" issue in the spec.
I believe the rest of the team took the same attitude. We used to talk about that a lot.
At the end of the day what you are asking for is impossible. The spec we worked to was a stack of paper 2 yards high when printed out. How many QA engineers know enough about flight dynamics to question if any of it is correct or not?
If you actually read the AD it will say "We are issuing this AD to prevent loss of all AC electrical power, which could result in loss of control of the airplane."
COULD lose control, not WILL. The 787 has at least 3 additional backup systems against this sort of failure, the APU, DC battery backup, and Ram Air Turbine.