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LATAM B773 complete electrical failure?

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LATAM B773 complete electrical failure?

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Old 6th Jan 2019, 16:21
  #81 (permalink)  
 
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Just wondering.
Considering how far down this aircraft was on the usable generator availability, would the old computer trick of rebooting be applicable to this situation?

I would not want to just try this in the wild without Boeing testing out and coming up with new procedures, but if in mid Ocean and unable to control fuel transfer, then I might reconsider.

Caution-Not type rated, but I have had occasion to fly jets without electrical power. They generally do not need electrical power to stay airborne- for a while!
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Old 6th Jan 2019, 17:02
  #82 (permalink)  
 
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Originally Posted by Machinbird View Post
would the old computer trick of rebooting be applicable to this situation?
Usually, that is discouraged in such situations. Closing a breaker into what might be a fault could result in even more serious damage. Cycling a circuit breaker can be OK to 'shake loose' a brain-dead processor. In that case, if you opened the breaker, you can close it (deferring to the published operating procedures, of course). But if it tripped on its own, I'd be hesitant to re-kindle a fire someplace.
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Old 6th Jan 2019, 22:49
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I was thinking something more like turning off all generator switches, and then bringing them back on line incrementally.
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Old 7th Jan 2019, 00:08
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Originally Posted by Machinbird View Post
I was thinking something more like turning off all generator switches, and then bringing them back on line incrementally.
Is that not what the existing system is expected to achieve, by isolating the faulty element?
I still do not understand what actually went wrong in this instance, the generators were green, but the distribution was on strike for some reason.
Turning off the generators might have helped, but it also might have left the system entirely powerless.
Think the crew performed splendidly and hope that the investigation is equally effective.
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Old 7th Jan 2019, 16:38
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I vaguely remember an incident back in the late 90’s on one of our 777s. They were minding their own business in the cruise when they stated getting EICAS advisories for lesser-known utilities. This turned quite rapidly into cautions, with many of the aircraft’s electrically powered systems going off line, to the point that it was looking pretty serious. I can’t recall how they got most of them back but the root cause was established later as being an ELMS failure. Interesting as it was still functioning but had a problem with some kind of feedback, so was load shedding on the basis of too much demand but carried on until it had turned off everything it could...
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Old 8th Jan 2019, 04:03
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Originally Posted by FullWings View Post
I vaguely remember an incident back in the late 90’s on one of our 777s. They were minding their own business in the cruise when they stated getting EICAS advisories for lesser-known utilities. This turned quite rapidly into cautions, with many of the aircraft’s electrically powered systems going off line, to the point that it was looking pretty serious. I can’t recall how they got most of them back but the root cause was established later as being an ELMS failure. Interesting as it was still functioning but had a problem with some kind of feedback, so was load shedding on the basis of too much demand but carried on until it had turned off everything it could...
So there is a precedent. Was it determined what the root cause was for the ELMS to go haywire in that case?
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Old 8th Jan 2019, 04:39
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ELMS Integrity

If indeed It is found to be a cascading ELMS failure is there merit in considering a software fix where ELMS is duplicated in the same way as the INS which is effectively "refereed" in many modern designs?
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Old 9th Jan 2019, 00:11
  #88 (permalink)  
 
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Originally Posted by Machinbird View Post
I was thinking something more like turning off all generator switches, and then bringing them back on line incrementally.
So far as I understand they lost both main AC busses. They did have generators available (there’s a picture of the system synoptic somewhere by the beginning of the post) but nowhere to connect them. Given the scenario, I don’t think that your suggestion would have made any difference. Hell even the RAT apparently didn’t engage to a bus! Is that bit of info confirmed? Usually the RAT feeds an essential bus or something different from the main busses. Having the RAT deployed but not powering its bus(ses) would be a true kick the nuts... Electrical system should’ve gone completely bat sh*t crazy somehow for this to happen
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Old 9th Jan 2019, 03:38
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Escape Path, everyone is entitled to their opinion but:
Originally Posted by belfrybat View Post
According to the commander, interviewed on TV, power came back after the engines were shut down. Presumably from the APU, on the footage the cabin lights were visible.
I'm leaning to the interpretation that the RAT dropped off on approach due to low airspeed at that point, but that it was energizing the appropriate DC busses until the approach. Otherwise, it seems the batteries would have been exhausted before the opportunity for the approach.

Is there even a switch or contactor that would even be able to shut down the RAT power once extended?

In any case, If I encountered such a problem inflight in mid-Ocean that was not covered in emergency procedures, training, or whatever, I would not just sit there wringing my hands.
This is not any form of criticism of the LATAM crew, who did an absolutely marvelous job. Didn't even flat spot the tires it seems.
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Old 9th Jan 2019, 18:41
  #90 (permalink)  
 
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So there is a precedent. Was it determined what the root cause was for the ELMS to go haywire in that case?
Can’t remember precisely - could have been something to do with load sensing? The net effect, as described above, was load shedding irrespective of the actual draw from the systems.

The LATAM incident sounds a little bit different as most of the busses went off, taking down what was attached to them, as opposed to commanded de-powering of selected units...
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