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Implications Of Total Avionics Loss T7---  
User currently offlineImperialEagle From United States of America, joined Jan 2006, 2605 posts, RR: 22
Posted (6 years 8 months 1 week 1 day 10 hours ago) and read 7101 times:
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In light of the BA T7 accident at LHR, just the rumor of a possible "TOTAL loss of power/avionics" leads to some interesting speculation. (Agreed---it is too soon to know what the real series of events leading up to the accident were.)

The most immediate effect I should think would be what the regulatory bodies would do in reagards to ETOPS rules.
Obviously a "TOTAL power/avionics loss" scenerio has been accounted for. No doubt the odds of such an even were considered nearly nill------untill it happens. So do they then re-think those rules, or does economics win out?

Also, the ability to control the T7 aircraft. Redundancy issues, etc.

What are your thoughts?


"If everything seems under control, you're just not going fast enough!"
76 replies: All unread, showing first 25:
 
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 1, posted (6 years 8 months 1 week 1 day 10 hours ago) and read 7094 times:



Quoting ImperialEagle (Thread starter):
The most immediate effect I should think would be what the regulatory bodies would do in reagards to ETOPS rules.

If it was really a total power failure (I have my doubts) then I think they'd have to suspend ETOPS for the fleet until they determined why. However, they won't do that until they know it was really a total power failure, at which point they may have a good idea of why, so that might not be necessary.

Quoting ImperialEagle (Thread starter):
Obviously a "TOTAL power/avionics loss" scenerio has been accounted for. No doubt the odds of such an even were considered nearly nill------untill it happens.

Actually, for a 777, it's supposed to be zero (not true of all aircraft). Not that it can't happen but, if it did, it would require so much additional damage to the airframe as to render the issue moot. To completely lose power on a 777 you need both engines to die, the APU to fail, the RAT to fail, and the battery to fail. All essentially independent systems.

Quoting ImperialEagle (Thread starter):
Also, the ability to control the T7 aircraft. Redundancy issues, etc.

The FBW system is triple redundant, so if it goes down about the only way I can see that happening is an external cause. So far, there isn't really any evidence I'm aware of that suggests they lost the FBW system. Loss of engine power and/or weather could have caused this type of event even with fully operational flight controls.

Tom.


User currently offlineTristarSteve From Sweden, joined Nov 2005, 4009 posts, RR: 33
Reply 2, posted (6 years 8 months 1 week 1 day 9 hours ago) and read 7034 times:

He may have lost all main power supplies due to engines running down, but muat have still had battery power. You can see that the APU door has opened, from the APU battery, so their must have been some battery supply.

User currently offlinePihero From France, joined Jan 2005, 4449 posts, RR: 76
Reply 3, posted (6 years 8 months 1 week 1 day 8 hours ago) and read 7005 times:
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Quoting TristarSteve (Reply 2):
You can see that the APU door has opened, from the APU battery, so their must have been some battery supply.

... but it is also likely the sign of a running APU, which makes the total electrical power loss even more remote.



Contrail designer
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 4, posted (6 years 8 months 1 week 1 day 8 hours ago) and read 6989 times:



Quoting Pihero (Reply 3):
Quoting TristarSteve (Reply 2):
You can see that the APU door has opened, from the APU battery, so their must have been some battery supply.

... but it is also likely the sign of a running APU, which makes the total electrical power loss even more remote.

Another thread brought up that the 777 has auto-APU capability. If an IDG drops offline, the APU automatically starts to pick up the load. First step is to open the door...it's possible the APU hadn't completed it's start sequence at the time of the event.

Tom.


User currently offlinePihero From France, joined Jan 2005, 4449 posts, RR: 76
Reply 5, posted (6 years 8 months 1 week 1 day 7 hours ago) and read 6939 times:
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Quoting Tdscanuck (Reply 4):
If an IDG drops offline, the APU automatically starts to pick up the load.

OK. But if I've lost TWO IDGs, the last thing I would want is an automatic APU start that would further deplete my batteries before I have a chance to assess my options. There must be something more to that effect, maybe dedicated batteries for the APU. ?..
(I've just checked : there's an APU battery, just aft of the aft cargo door..., so your post could very well be correct as to the position of the APU door.)
But I'm not buying the double engine failure scenario anyway.

[Edited 2008-01-17 14:24:03]


Contrail designer
User currently offlineZANL188 From United States of America, joined Oct 2006, 3525 posts, RR: 0
Reply 6, posted (6 years 8 months 1 week 1 day 5 hours ago) and read 6900 times:
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Quoting Pihero (Reply 5):
But I'm not buying the double engine failure scenario anyway.

It's happened before....



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User currently offlineAviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 41
Reply 7, posted (6 years 8 months 1 week 1 day 5 hours ago) and read 6879 times:



Quoting Tdscanuck (Reply 4):
the APU automatically starts to pick up the load.

Only possible at relative low altitude.
If I am not mistaken the Boeing flight manual says not even to try an APU start at a certain altitude as it would only drain the battery without much chance of an actual APU start.
Don't know the exact details but I am sure there is a driver out there to fill me in.

Quoting Pihero (Reply 5):
the last thing I would want is an automatic APU start that would further deplete my batteries before I have a chance to assess my options

 checkmark 

Further a total PWR failure sounds very unlikely.
The emergency bus is independend of IDG's and APU.

I do know one incident with an A320(somewhere above the UK) which was unable to leave a holding pattern due to freaked out autopilot.
They had to shut down all electrical power and restart it to gain control again albeit manual this time.
Not really funny I guess as the IRS is then lost as well and won't come back online.



The truth lives in one’s mind, it doesn’t really exist
User currently offlineXT6Wagon From United States of America, joined Feb 2007, 3409 posts, RR: 4
Reply 8, posted (6 years 8 months 1 week 1 day 1 hour ago) and read 6776 times:



Quoting Pihero (Reply 5):
OK. But if I've lost TWO IDGs, the last thing I would want is an automatic APU start that would further deplete my batteries before I have a chance to assess my options. There must be something more to that effect, maybe dedicated batteries for the APU. ?..

I believe that the APU is required to have a pyrotechnic starter for just such a case so it wouldn't be pulling much power at all from its battery.


User currently offlineTristarSteve From Sweden, joined Nov 2005, 4009 posts, RR: 33
Reply 9, posted (6 years 8 months 1 week 21 hours ago) and read 6716 times:



Quoting XT6Wagon (Reply 8):
believe that the APU is required to have a pyrotechnic starter for just such a case so it wouldn't be pulling much power at all from its battery.

The B777 APU has two starter motors. Normal start is by a pneumatic starter that takes air from the aircraft pneumatic system. If this pressure is not available then there is an electric starter which takes over powered by the APU battery.
I have never seen a pyrotechnic starter on an airliner.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 10, posted (6 years 8 months 1 week 20 hours ago) and read 6702 times:

Any Preliminary report officially declared as yet.
regds
MEL



Think of the brighter side!
User currently offlineFaro From Egypt, joined Aug 2007, 1548 posts, RR: 0
Reply 11, posted (6 years 8 months 1 week 13 hours ago) and read 6604 times:

Out of pure speculation, what if I bombard an aircraft on final approach with huge doses of electro-magnetic radiation (I believe such a weapon was once envisaged if not tested) and try to fry the electric circuits? Would it do enough damage to disable control of my engines, FBW and other electrically-controlled systems?

Faro



The chalice not my son
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 12, posted (6 years 8 months 1 week 10 hours ago) and read 6497 times:



Quoting Faro (Reply 11):
what if I bombard an aircraft on final approach with huge doses of electro-magnetic radiation (I believe such a weapon was once envisaged if not tested) and try to fry the electric circuits? Would it do enough damage to disable control of my engines, FBW and other electrically-controlled systems?

An aluminum airliner makes a very nice Faraday cage. You'd probably nuke the radios and navigation equipment, but I don't know if the engines or FBW would care.

Tom.


User currently offlineZeke From Hong Kong, joined Dec 2006, 9105 posts, RR: 75
Reply 13, posted (6 years 8 months 6 days 19 hours ago) and read 6357 times:



Quoting HAWK21M (Reply 10):
Any Preliminary report officially declared as yet.

AAIB released an initial report http://www.aaib.dft.gov.uk/latest_ne..._january_2008___initial_report.cfm



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 14, posted (6 years 8 months 6 days 12 hours ago) and read 6281 times:



Quoting Zeke (Reply 13):

Thanks.
So 600Ft & 2 miles out something caused loss of Thrust in both Engines.
regds
MEL



Think of the brighter side!
User currently offlineBWilliams From United States of America, joined Sep 2007, 212 posts, RR: 0
Reply 15, posted (6 years 8 months 6 days 11 hours ago) and read 6243 times:



Quoting HAWK21M (Reply 14):
So 600Ft & 2 miles out something caused loss of Thrust in both Engines.

Interesting.

What could cause this? Obviously, the problem wouldn't be in the engine's FADEC unit, since a dual failure is a near-impossibility. Could an electrical problem (short or severed wire) in the throttle quadrant cause throttle position changes both manually and through the Auto-thottle, or are those totally independant circuits. indicating a larger problem?



Regards, Brad Williams
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 16, posted (6 years 8 months 6 days 8 hours ago) and read 6201 times:



Quoting BWilliams (Reply 15):
What could cause this

Im Thinking Flock of birds.
Hows the Bird situation out there.
regds
MEL



Think of the brighter side!
User currently offlineStarglider From Netherlands, joined Sep 2006, 678 posts, RR: 44
Reply 17, posted (6 years 8 months 6 days 7 hours ago) and read 6163 times:

Quoting HAWK21M (Reply 16):
Quoting BWilliams (Reply 15):
What could cause this

Im Thinking Flock of birds.
Hows the Bird situation out there.

No evidence of bird impact anywhere on the engines, wing leading edges or nose of the aircraft when viewing detailed photographs recently published .

What ever the source of the failure, it somehow may have affected engine related units interfaced to the left and right systems ARINC buses and in this case affected both buses at the same time. Units related to engine control such as:

EEC (engine electronic control),
WOW (weight on wheels cards),
ADIRU (Air Data Inertial Reference Unit),
EDIU (Engine Data Interface Unit),
ACIPS (Airfoil and Cowl Ice protection System)
are interfaced through these buses.

Left bus for the left engine and right bus for the right engine.

Next question is if the source that caused the dual failure is from an aircraft related system or external, either inside the aircraft or the outside world. Either way, since this is such a very rare event, could EMI be a factor to reccon with in this case?

I stress this is pure speculation of course, too early to draw any conclusion.


Starglider

[Edited 2008-01-19 13:36:23]

User currently onlineWingedMigrator From United States of America, joined Oct 2005, 2214 posts, RR: 56
Reply 18, posted (6 years 8 months 6 days 6 hours ago) and read 6119 times:



Quoting Starglider (Reply 17):
What ever the source of the failure, it somehow may have affected engine related units interfaced to the left and right systems ARINC buses and in this case affected both buses at the same time.

Are the buses 100% mechanically redundant (not just electrically redundant), i.e. could a single loose connector take both of them down? Seems very far-fetched to me... but envisioning a common avionics failure mode is quite baffling.


User currently offlineFADECFAULT From United States of America, joined Nov 2007, 70 posts, RR: 0
Reply 19, posted (6 years 8 months 6 days 4 hours ago) and read 6077 times:

I'm sure I'll be flamed but any talk is just pure baseless speculation:

I'll gander it was pilot error. Pilots failed to notice A/T kicked off during final and manually pushed the throttle too late.

Like I said totally baseless but I have a hard time believing that both engines just failed to respond. Correct me if I'm wrong but the engines have their own PMA's and do not rely on a/c power off eec operation (except for alternate pwr). So even with total power failure wouldn't the engines continue to operate normally?


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 20, posted (6 years 8 months 6 days 3 hours ago) and read 6062 times:



Quoting FADECFAULT (Reply 19):
I'm sure I'll be flamed but any talk is just pure baseless speculation:

I'll gander it was pilot error. Pilots failed to notice A/T kicked off during final and manually pushed the throttle too late.

Like I said totally baseless but I have a hard time believing that both engines just failed to respond. Correct me if I'm wrong but the engines have their own PMA's and do not rely on a/c power off eec operation (except for alternate pwr). So even with total power failure wouldn't the engines continue to operate normally?

Just where did you get this idea from? I'd suggest keeping this kind of baseless theorising to yourself.

The AAIB initial report makes no mention of the A/T being kicked off. On the contrary, it mentions that the A/T twice tried to increase thrust with no response and that the crew then manually advanced the thrust levers, also with no response.

You are implying the flight crew are covering up an error. They would be doing this in the full knowledge that the flight recorder data would find them out when analysed. Also BA would not risk parading the crew in front of the press if there was the slightest suspicion of pilot error.

The AAIB report also makes no mention of any electrical power loss, which might make this entire thread irrelevant.  Wink



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 21, posted (6 years 8 months 6 days 1 hour ago) and read 6049 times:

The sudden loss of thrust & no response to Thrust recovery is a concern if its an Aircraft related fault.
This is one mystery.
Read somewhere that Russian Intelligence has qouted as being an Electro magnetic attack on the wrong plane rather than the PMs Aircraft.

Not sure about how that works.

regds
MEL



Think of the brighter side!
User currently offlineFxfan From United States of America, joined Oct 2006, 85 posts, RR: 0
Reply 22, posted (6 years 8 months 5 days 9 hours ago) and read 5921 times:

Sorry to ask such a simple question, but could someone give a basic explanation of how the engine controls are linked to the engines themselves. Obviously fully automated but are there mechanical backups?

User currently offlineMD11Engineer From Germany, joined Oct 2003, 14026 posts, RR: 62
Reply 23, posted (6 years 8 months 5 days 9 hours ago) and read 5909 times:

If the B777 works like all FADEC controlled aircraft I have so far been working on, the FADEC has two independent channels (actually two seperate computer circuit boards each with it's own processor). ERach circuit board gets powered by it's own power source (a small alternator attached to the engine gear box, actually two altenators in one housing). For gound maintenance use (when the engines are not running) there should be another alternate power source from the airframe.
The throttle levers normally operate two independent resolvers each, one for each FADEC channel. These resolvers receive their power from the FADEC. e.g. totally independent of airframe power.

Jan


User currently offlineStitch From United States of America, joined Jul 2005, 31003 posts, RR: 86
Reply 24, posted (6 years 8 months 5 days 8 hours ago) and read 5895 times:
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Quoting ImperialEagle (Thread starter):
The most immediate effect I should think would be what the regulatory bodies would do in reagards to ETOPS rules.

Three-engined and four-engined planes have had complete avionics and power losses, yet they are still allowed to fly long distances. So I don't see why a two-engined plane should suddenly be denied the right to fly long distances.

If it had been a BA DC-10 or 747, would we be demanding BA ground their TATL ops?


25 Post contains images Avioniker : Anybody besides me notice that the fan is only relatively slightly fractured on the #1 engine and the #2 appears intact? Or is there a property of the
26 MD11Engineer : On the 737NG and other aircraft, the HP valve in the HMU is closed by a solenoid, which receives power from the airframe electric system. A power fai
27 Starlionblue : Indeed. Very logical. As I said in Part 6 the 777 fleet has been flying safely for 13 years. Now we have one crash. Doesn't it seem more likely somet
28 Jetlagged : Very true, and had an avionics problem struck the 777 in cruise it would most likely have recovered and been able to continue flying. ETOPS is primar
29 Kstatepilot : What I am wondering is where anybody has said that there is a power loss? All that we know is that the engines were working, and they failed to increa
30 GoBoeing : I don't want to sound like a jerk here but if any FO did not have the presence of mind to do just that in the situation this plane was in, they would
31 Fr8mech : The list of things that can affect both engines on a twin is remarkable short. -Fuel -Pilots -A/T There may be a couple more, but none come to mind. I
32 BWilliams : Exactly. That's why I posited the question of damage to the electronics in the throttle quadrant instead of the actual engine EEC/ECU. Would the engi
33 Starglider : If fuel, what about fuel/pilots: Highly unlikely but engines not responding to thrust due to some command, how about erroneously selecting both fuel
34 Post contains images Starlionblue : You forgot alien space bats. That is, external factors. But apart from canada goose aerobatics teams, I find it hard to believe an external factor co
35 MD11Engineer : We were trying to figure which fault would make BOTH engines not accept a increease of thrust command. Due to the explanations by some people Does an
36 Post contains images Avioniker : I'd not say you sound like a jerk. . . The FO stated in his interview, reprised on BBC yesterday, that he cleared the A20 by about 20ft. Lowering the
37 Fr8mech : You're right, I did not list external factors, because, short of bird or lightning strike, nothing external, at 600' AGL, should affect both engines
38 777WT : back then BA did suffer a avionics fire in one of the 777 which landed in the US.
39 MD11Engineer : I should have been more specific: I meant, of course, one A/T servo for each throttle, so that they can move independently (necessary e.g. if an engi
40 FADECFAULT : Def need someone with 777 experience in here. The 757 and 767 had a TMC - thrust management computer to control A/T (don't remember if direct or indi
41 MD11Engineer : Sure, but a failed TMC would not explain why the engines also refused to increase thrust when the throttles were firewalled manually by the pilots. O
42 FADECFAULT : I agree with you, I do not understand how both engines somehow refused to give more power. All essential systems have redundent back ups (dual channe
43 Tdscanuck : They're supposed to be. Given the number of wires and connectors involved it's entirely possible that there is a common connector somewhere, but ther
44 MD11Engineer : It seems from this information that the B777 is a completely different bird than all those I have worked on before. The way I understand is that thro
45 Starglider : Like said, highly unlikely. I can't imagine knocking those switches to the cutoff position by accident, even though the fuel control module is right
46 TristarSteve : Yes. I work B777, I have an EASA B1 licence on it. I try to help with the discussions here, but because the systems are so complicated it is difficul
47 HAWK21M : You seem to be the right person to have a more realistic view on what could have gone wrong. regds MEL
48 Tdscanuck : There's also a detent on the cutoff levers so you need to move them back then sideways then down to close the valves. Dumber things have been done on
49 WestWing : Which is of course why, from a human factors engineering standpoint, the landing gear lever feels like a wheel and different to the touch than the fl
50 A10WARTHOG : I read one article today, not sure who it was, that said nothing out a total power loss, just that the engine did not produce the thrust. It said that
51 Post contains links and images Jetlagged : I thought they were toggle switches, needing to be lifted up to open or close (as on the 747-400). View Large View MediumPhoto © Oliver Brunke E
52 TristarSteve : They are. You pull them up towards you then move. The starry shape on the ends is to let the red light shine through on fire warning.
53 Tdscanuck : No. Although nobody has come out and said it, the preliminary reports strongly suggest that there was no loss of electrics (since none of them mentio
54 Aviopic : I received the following story by email, guess it has been published somewhere already but for those(like me) who were unable to find it. An electroni
55 Tdscanuck : On the whole, this is a pretty good article, but this portion is bonkers. The 777 (and 737, 757, and 767) does not transfer fuel between tanks in fli
56 Post contains images Aviopic : Don't shoot the messenger From the technical side. What is the reason for not having a fuel transfer option ? I would think that in a single engine s
57 Starglider : The incident i referred to was long after the introduction of the wheel on the gear- and airfoil shape on the flap lever. Indeed human factors, due t
58 Starlionblue : This just sounds like a description of coffin corner.
59 Fr8Mech : In single engine operation, or even in the event of an imbalance caused by some other factor, the flight crew can select any tank to any engine, thro
60 Tdscanuck : Fuel transfer isn't needed...due to certification requirements about puncturing a fuel tank during a tire burst, there is enough aileron authority to
61 Zeke : Fuel balancing can by done on the 777 in any phase of flight, it is not restricted to single engine ops. "FUEL IMBALANCE When the fuel quantity in le
62 Fr8Mech : Fuel balancing is not fuel transfer. Fuel balancing is accomplished by allowing both engines to burn one tank until balance is acheived. Fuel transfe
63 Zeke : I seem to recall fuel transfer switch/button on the 744.....pretty sure as well on the classic you could transfer via the jettison gallery.
64 Post contains links WestWing : Thanks. AAIB have issued an update which makes no mention of any loss of electrics/avionics either.
65 Fr8Mech : Transferring via the jettison manifold is only performed during jettison (or on the ground when someone knows what they're doing), it is not approved
66 Tdscanuck : As noted, fuel balancing isn't done by moving tank to tank, it's done by burning both engines off one tank until balance is restored. Boeing twins do
67 Post contains images Avioniker : I stand corrected (sort of), on one count anyway. . .   [Edited 2008-01-24 10:09:20]
68 BWilliams : I might just be missing it, but what are you trying to show with those pictures?
69 HAWK21M : Heard one Pax had a broken foot,any idea how he was evacuated & when.Just curious. regds MEL
70 Post contains images Avioniker : On the #1 engine you'll note the fan is sheared symmetrically indicating it was powered as the fan case crushed up from the contact with the ground.
71 Post contains images Avioniker : ATW Daily News UK investigators confirm BA 777 engines failed to respond to commands Friday January 25, 2008 UK Air Accidents Investigation Branch iss
72 Phollingsworth : If they are like those on the 767 they are pulled up and out before you can close them. The original design was just a toggle; however, these were al
73 Jetlagged : That is exactly what I meant. A toggle switch has to be pulled out, over a metal gate before it can be moved down. The gate can be shaped so that the
74 Starglider : With reference to reply 57: The mentioned 4 relays per engine control many functions (obviously split between the 4 to ensure redundancy). Some that c
75 HAWK21M : Now its getting more & more mysterious & serious.Was there an Alert SB issued? regds MEL.
76 Starglider : Who knows, perhaps a certain subsystem failed or its shielding was breached which "confused" other systems communicating with each other in the fuel
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