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> But those engineers determined that their fix would only successfully transition the helicopter into flight mode 85% of the time. So Thursday's attempt may have fallen into the 15% of instances in which it doesn't work.

I really hope we get to see the postmortem on this. Any guesses what kind of software issue could cause a known but not fixable 15% error rate?

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I suspect it’s a hard real-time, timing/synchronicity type issue between multiple systems. System A responsible for motor control and System B responsible for power management, both need to talk to each other and talk to System C for flight control, and even with bugs fixed, the hardware watchdog timer may not get a response fast enough from A,B, and C in order to meet the deadlines necessary for system safety.

The percentage represents the probability that multiplying the variance in response timing of all the systems will result in the conditions that produce the watchdog timing error will occur.

I was wondering about that, and if maybe they're just talking about the probability of the fix having worked in a clunky way.

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