US aviation authority: Boeing 787 bug could cause 'loss of control'

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“We are issuing this AD [airworthiness directive] to prevent loss of all AC electrical power, which could result in loss of control of the aeroplane,” said the Federal Aviation Administration directive. “If the four main generator control units (associated with the engine-mounted generators) were powered up at the same time, after 248 days of continuous power, all four GCUs will go into failsafe mode at the same time, resulting in a loss of all AC electrical power regardless of flight phase.”

I honestly think this is a non-issue but because its 787 related it makes the news. The fault was found in Lab tests and has not affected the airframe in the field. I cant imagine a plane being left on for 248 days without some kind of power down.

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It wouldn't cause a loss of control, even on takeoff or landing. By the time there was a chance of that happening, the RAT would have deployed, and they'd have emergency power to the flight controls. Never miss a chance for fear mongering though.

No commercial aircraft is ever going to me powered up 24/7 for 8 months. But since it happened in the lab, this gets notice out to be sure.

a reply to: Zaphod58

I found a similar bug in Cadence once. It required me to have some unlikely magic combination of factors, sort of like this one. Instead of 8 short of 256 like this, I had to hit a particular even binary boundary of nets and nodes. They thought it couldn't happen.

They don't know me very well. It was something creepy like 8192 nets and 32,768 vertices at the same time (not the actual #). I, of course, did it by accident.

The ultimate question. Is this the only way for the problem to surface? Many times bugs have multiple ways to to be found. After you find the first one it pays to keep searching for other ways for the issue to occur. That's the scary part about troubleshooting problems. The more you find the more you have to look and other things come to light.

a reply to: datasdream

They've been checking systems for several years and this is currently the only way that they have seen it occur to date. There may be others, but none have cropped up yet.

a reply to: Zaphod58

What is the rat system you referred to?
Does it work in conjunction with auto-pilot?

a reply to: loveguy

The RAT is the Ram Air Turbine. It's basically a windmill that drops down under the aircraft if the aircraft loses all electrical power to provide at least enough power for instruments and flight controls.

a reply to: Zaphod58

Whoa!

That is extremely cool!

a reply to: grey580

There are a number of videos on YouTube of Boeing test flights where they come back with it deployed. They actually had to redesign it on the 787.

a reply to: Zaphod58

Do commercial airlines ever get fueled with engines running, other than some extreme circumstance?

a reply to: roadgravel

I don't want to say a definitive no, but it's extremely rare and pretty much would only be if the APU was inop and they didn't have ground equipment.

originally posted by: roadgravel
a reply to: Zaphod58

Do commercial airlines ever get fueled with engines running, other than some extreme circumstance?

As Zap noted, it would be rare to re-fuel with engines running. Since they are continuous combustion engines, turbine engines can technically run on fuel vapors if the concentration is high enough.

Not too long ago, Detroit Diesel offered 2-stroke diesel engines for use in semi-tractor trailers and those often found use in the delivery trucks to the local gas stations. More than once, drivers have left the engine on while filling the station tanks and the vapors released caused the engine to race and over-speed... no way to shut it off due to it sucking in fuel as vapor.