777 Total Electrical Failure - then what?
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SpaceRanger
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From: Samsonite
777 Total Electrical Failure - then what?
Despite all the redundancy, what would happen to a 777 experiencing total electrical failure?
Many systems are electrically powered, including flight controls. But if there isn't any electrical power?
If some major failure, explosion or other extreme event happened in a critical place, like in the MEC, which totally fries the electrical system - and renders all generators, RAT, batteries, and buses useless in an instant.
I know it is "impossible" with all the redundancy, but so was the triple redundancy on the DC-10 hydraulic systems - yet a single failure took out all three systems. So just for a moment, presume all electrical power is lost (apart from autonomous systems, like the engines, ELT, flashlights, Rescue 406 etc)
Aircraft is until the time of that event on auto pilot and in trim.
What will happen to
Many systems are electrically powered, including flight controls. But if there isn't any electrical power?
If some major failure, explosion or other extreme event happened in a critical place, like in the MEC, which totally fries the electrical system - and renders all generators, RAT, batteries, and buses useless in an instant.
I know it is "impossible" with all the redundancy, but so was the triple redundancy on the DC-10 hydraulic systems - yet a single failure took out all three systems. So just for a moment, presume all electrical power is lost (apart from autonomous systems, like the engines, ELT, flashlights, Rescue 406 etc)
Aircraft is until the time of that event on auto pilot and in trim.
What will happen to
Last edited by TheDrop; 13th March 2014 at 13:13.
Joined: Jun 2002
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From: Geneva, Switzerland
777 Total Electrical Failure - then what?
I would say that complete electrical failure = major structural failure. To get there you would have some (chain of) events that will imply that the aircraft is otherwise significantly crippled. I don't think there is any other scenario possible, however improbable.
Joined: Mar 2008
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From: Malvern, UK
I would say that complete electrical failure = major structural failure. To get there you would have some (chain of) events that will imply that the aircraft is otherwise significantly crippled. I don't think there is any other scenario possible, however improbable.
Thread Starter
SpaceRanger
Joined: May 1999
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From: Samsonite
Fly the aircraft. That would be your main concern. What if flight controls didn't even respond?
Imagine the scenario, all goes black, and all you have is your flashlight and the light of the stars and moon, if at all. Emergency lights may work?
EDITED
Imagine the scenario, all goes black, and all you have is your flashlight and the light of the stars and moon, if at all. Emergency lights may work?
EDITED
Last edited by TheDrop; 13th March 2014 at 13:34.
Thread Starter
SpaceRanger
Joined: May 1999
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From: Samsonite
Yes, you are right, I deleted that part.
Shouldn't we know our systems well enough to know what options we have in such situations?
Do you know your own aircraft type well enough to answer the questions above?
Shouldn't we know our systems well enough to know what options we have in such situations?
Do you know your own aircraft type well enough to answer the questions above?
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From: Smogsville
Engines would still run - suction feed.
Engine thrust levers "MAY" work as the thrust lever resolvers are powered by the EEC. (But doubtful).
Hydraulics ok - engines running.
Packs still run - power fail, they fail ON/RUN however the packs would go to high flow and over pressurise the cabin as the pressure control system would have stopped, the over pressure relief valves which are mechanical would open around 9.2psi
Flight controls - mechanical cable input to one spoiler each wing & stabiliser via the manual stab trim levers and all possible with hydraulics available.
Fortunately the A/C should be in trim and speed stable.
Reasons for complete power failure.
1. Oxy bottle explosion like the QF 744 (other thread confirms location of oxy bottle in the 777 is next to the MEC).
2. Galley water leak flooding the MEC, once again a QF 744 that ended up on battery power.
3. Decompression near the MEC causing structural damage to the MEC and therefore it's failure.
1. Would lead the cockpit crew unconscious & the A/C drifting through the sky for who knows how long and in which direction.
2. Crew able to fly but effectively lost, stby compass only, ISFD would fail without power.
3. Would be a combination of possibly 1 & 2.
All cases extremely difficult to pull off successfully without a fantastic moonlit visual night for visual reference.
Engine thrust levers "MAY" work as the thrust lever resolvers are powered by the EEC. (But doubtful).
Hydraulics ok - engines running.
Packs still run - power fail, they fail ON/RUN however the packs would go to high flow and over pressurise the cabin as the pressure control system would have stopped, the over pressure relief valves which are mechanical would open around 9.2psi
Flight controls - mechanical cable input to one spoiler each wing & stabiliser via the manual stab trim levers and all possible with hydraulics available.
Fortunately the A/C should be in trim and speed stable.
Reasons for complete power failure.
1. Oxy bottle explosion like the QF 744 (other thread confirms location of oxy bottle in the 777 is next to the MEC).
2. Galley water leak flooding the MEC, once again a QF 744 that ended up on battery power.
3. Decompression near the MEC causing structural damage to the MEC and therefore it's failure.
1. Would lead the cockpit crew unconscious & the A/C drifting through the sky for who knows how long and in which direction.
2. Crew able to fly but effectively lost, stby compass only, ISFD would fail without power.
3. Would be a combination of possibly 1 & 2.
All cases extremely difficult to pull off successfully without a fantastic moonlit visual night for visual reference.
Last edited by SMOC; 13th March 2014 at 14:40.
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From: Big Sky Country
Not all the critical boxes are in the MEC. Some are stashed in the forward cargo sidewalls to give limited flight controls. The RAT should auto deploy and/or APU auto start.
So.....You will have limited flight controls. Might be a dark cockpit, but the engines are self contained and will keep running. EEC's powered by the dedicated generator on the engine. Whiskey compass will work to give you a dead reckoning course. The rest will involve a bit of luck!
So.....You will have limited flight controls. Might be a dark cockpit, but the engines are self contained and will keep running. EEC's powered by the dedicated generator on the engine. Whiskey compass will work to give you a dead reckoning course. The rest will involve a bit of luck!
Thread Starter
SpaceRanger
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From: Samsonite
Air Accidents Investigation: N786UA Report Sections
United Airlines had a fire in the MEC, while they were on the ground, just around push-back.
What if they had experienced this same problem in flight?
If there is a major disturbance in the MEC, either fire, explosion, flooding - how can you discount a total electrical failure?
United Airlines had a fire in the MEC, while they were on the ground, just around push-back.
What if they had experienced this same problem in flight?
If there is a major disturbance in the MEC, either fire, explosion, flooding - how can you discount a total electrical failure?
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From: Everett, WA
Engines would still run - suction feed.
Engine thrust levers "MAY" work as the thrust lever resolvers are powered by the EEC. (But doubtful).
Why do you say 'But doubtful'? EEC is powered by a dedicated engine generator, 100% independent of the aircraft power system, and thrust set is determined by the actual throttle position, as determined by the EEC driven throttle resolver (as you correctly noted).
Assuming suction feed works (may or may not, depending on altitude and how 'weathered' the fuel is (i.e. how long it's been at altitude, and how much air is still dissolved in the fuel), the only thing that would prevent the engines from operating more or less normally is if the throttle resolver wiring between the flight deck and EEC was severed.
BTW, the 777 has, on each engine (in addition to the dedicated EEC power source), a 'normal' IDG, a VSCF (each engine's VSCF capable of powering the aircraft critical system), and a dedicated FBW generator. Oh, and addition to the battery there is a generator on the RAT. Within the EE bay, redundant systems are separated by a minimum distance (it's been a long time since I worked the 777 development, but 5 feet sticks in my mind).
Baring something really nasty happening in the EE bay (such as a large bomb blast), there is simply no way to loose all those redundant, independent systems at more or less the same time.
Engine thrust levers "MAY" work as the thrust lever resolvers are powered by the EEC. (But doubtful).
Why do you say 'But doubtful'? EEC is powered by a dedicated engine generator, 100% independent of the aircraft power system, and thrust set is determined by the actual throttle position, as determined by the EEC driven throttle resolver (as you correctly noted).
Assuming suction feed works (may or may not, depending on altitude and how 'weathered' the fuel is (i.e. how long it's been at altitude, and how much air is still dissolved in the fuel), the only thing that would prevent the engines from operating more or less normally is if the throttle resolver wiring between the flight deck and EEC was severed.
BTW, the 777 has, on each engine (in addition to the dedicated EEC power source), a 'normal' IDG, a VSCF (each engine's VSCF capable of powering the aircraft critical system), and a dedicated FBW generator. Oh, and addition to the battery there is a generator on the RAT. Within the EE bay, redundant systems are separated by a minimum distance (it's been a long time since I worked the 777 development, but 5 feet sticks in my mind).
Baring something really nasty happening in the EE bay (such as a large bomb blast), there is simply no way to loose all those redundant, independent systems at more or less the same time.
Joined: Jan 2011
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From: Seattle
LME (GOD):
Following the loss of all navigation equipment, I think any resourceful flight crew would round up some PAX iPhones with GPS and head for somewhere with a runway. And once within range of cell service, phone in with their status.
Whiskey compass will work to give you a dead reckoning course. The rest will involve a bit of luck!
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From: Smogsville
Why do you say 'But doubtful'?
