A Boeing 787 powered on for 248 days could lose all AC power

transcript

Leave a Boeing 787 powered on for 248 days. It could lose all its AC power. Even in flight.

The 787's generators are run by small computers. Generator control units. Inside each one, a software counter. After 248 days of power, it overflows. That unit drops into failsafe mode. Powered up together? All four hit day 248 together. All four fail at once. All AC power, lost.

248 days of continuous power. Four units, failing in the same moment. The FAA warned: it can mean loss of control of the airplane.

But here's the good part. It turned up in laboratory testing, and Boeing told the FAA. And the FAA's fix wasn't new software.

From 1 May 2015, the FAA requires a repeating task. Power the airplane down. At least every 120 days. Well inside 248. One work-hour. 85 dollars. For 28 US planes.

The FAA called it interim action. Turn it off and on again. Meanwhile, Boeing was building the real fix. A software upgrade.

Every counter that only goes up hits a limit someday. Start identical parts together, and they hit it together. Test past it.

Full story in the article.