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Boeing's Dreamliner Has a Bug That Can Make It Lose Power Mid-Air

Illustration for article titled Boeings Dreamliner Has a Bug That Can Make It Lose Power Mid-Air

Here’s yet another snag for the embattled Boeing 787 Dreamliner: The Federal Aviation Administration today warned of an alarming software glitch, in which the AC power can cut out and cause the pilot to lose control in the middle of a flight.

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The bug was revealed by tests by the Boeing laboratory, thank god, and not by some real world accident. If the plane is not powered down regularly between flights, its generator systems could switch into fail-safe mode, which would cut all AC electrical power. That could happen even if the plane were mid-air.

It does take 248 days of continuous power before triggering the software glitch, and planes are unlikely to stay powered on for that long under regular maintenance. But, as the WSJ notes, the Dreamliner has run into other technical glitches, which were often worst right after powering up. Boeing has suggested allowing extra time for the plane to boot up, but in practice, airlines sometimes just keep the planes on to avoid the extra headache.

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The FAA and Boeing have now both issued announcements on the importance of regularly powering down the aircraft. Hopefully, the danger of this bug will remain a hypothetical one.

[Wall Street Journal, FAA]

Top image: AP Photo/Elaine Thompson

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DISCUSSION

So if anyone’s wondering, the biggest signed number you can hold in a standard 32-bit integer is 2,147,483,727. Which is

248 days * 24 hours * 3600 seconds * 100 centiseconds

Basically they’ve got a 100th of a second timer where they’re incrementing a timestamp. And then it rolls over from positive to negative. Aieeee, suddenly you’re 496 days in the past!

This is really easy to handle in software as long as you realize it’s a problem. So either they didn’t think of it or they didn’t think it would possibly go 248 days without being rebooted.