Desk Jockey

BA have been paid out and the hull is now owned by the insurance company. Source- BA staff briefing.(Weeks ago, as previously reported here.)

Green-dot

Quoting Chris Scott:

Quote:

What I have deliberately left out so far, in accordance with the AAIB Bulletin, are the spar valve control relays that you are concerned about. Are they relevant? You say that they are downstream of the run/cut-off relays, and are directly controlled by the fire handles. This seems to be at odds with the AAIB’s explanation. Are you saying that they are normally sequenced to the valve-open position by the run/cut-off relays? Are you proposing that they are possible candidates for RF interference?

Chris,
Yes, the spar valve control relays are relevant. The AAIB wrote that, i quote: "Examination and tests of the wiring identified that, in the case of the right engine, the valve CLOSE wire from the run/cut-off relay was still continuous." (Here i assume they mean the spar valve circuit not the engine shut off valve circuit because the header on page 5 refers to spar valves not SOVs)

Without reading anything more into it than what the AAIB wrote here, this could imply that from the run/cut-off relay (which is inside the right power management panel, part of ELMS), the CLOSE wire downstream, right up to the spar valve, had continuity. The relevance here, with the run/cut-off relay in the OPEN position, is that in order to be able to measure continuity on the CLOSE wire right up to the valve implies that the path has to go through the right spar valve control relay which had to be in a closed position in order to measure continuity right up to the spar valve.

Normally, under the conditions described by the AAIB, one would expect that control relay to be open, similar to the run/cut-off relay. They are in the same path (the control relay somewhere between the run/cut-off relay and the spar valve). The fire switch, when selected from "Normal" to "Fire", isolates the above mentioned relay circuit. The wire making the "Normal" circuit is directly connected to the control relay, not the run/cut-off relay. When the switch is selected to the "Fire" position it isolates the "Normal" relay circuit and feeds a close signal directly via a second (separate) wire path to the spar valve if all functions as expected (to be clear, this is the pre SB 777-28-0025 situation valid for G-YMMM as the AAIB explained and makes sequencing important). The 28V dc power source is connected to the fire switch. With the fire switch in "Normal" position, power is supplied to the normal run/cut-off circuit and the second wire path is isolated.

The AAIB, since they mentioned the run/cutoff relay, therefore did not refer to measuring continuity in the second (switch in "Fire" position) wire path but in the "Normal" wire path, which, as explained has to inevitably go through the control relay.

Regards,
Green-dot

Sunfish

Desk Jockey:

My sources are names at Lloyds who have to put their hands in their pockets if their syndicate has a share in BA's policy.

As of last week my sources tell me they have not had to put their hand in their pockets yet, and they would know.

BA has certainly advised Lloyds. The hull has been assessed as a total loss, however my information is that it will be necessary for the insurers to receive the accident report before a claim is made and accepted because of the possibility of cross claims against the insurers of the Beijing airport (if its fuel), Boeing (If its a system stuffup), contributory negligence by BA or Rolls Royce.

However it's all only rumour and I wouldn't know. As for lloyds, yes they are merely insurers, but the have an infinitely subtle and world wide intelligence network made up of every name on the floor. I would not ignore Lloyd's.

Southernboy

It seem entirely logical that insurers will withhold payment until the AAIB report is published. There will be clauses in the policy that depend on cause.

If, for example, negligence were to be proven, the insurer will either limit payment or block it altogether.

PBL

Sunfish,

I don't wish to question either your contacts or your very interesting information about what is going the rounds in the insurance business. But we must distinguish between effects that obey the general laws of terrestial electromagnetic physics, and magic.

You are right about both of those. It is well known how easy it is to jam GPS signals. I suspect you can buy jammers for a couple hundred dollars at most. It is also well known (if one reads Aviation Week, for example) that the military in Iraq is deploying electronic warfare devices to disrupt IED control. However, both these phenomena consist of disturbing radio signals. Causing a disturbance in well-shielded on-board electronics from a point at least many hundreds of feet away is something else entirely.

To employ an analogy I have used before: it is one thing to ruin the picture on a television set by turning on your vacuum cleaner; it would be something else entirely to get your vacuum cleaner to change the channels.

If there was any EMI coming from outside the aircraft, it remains to be explained how it can have happened without leaving any trace at all in the highly-instrumented and recorded electrical and electronic control systems of the aircraft. If you explode a grenade sufficient to collapse your garden shed, it leaves a hole. No one would mistake such an event for, say, your shed collapsing spontaneously. Exactly the same is true of electromagnetic radiation. And the AAIB has said they have seen no control anomalies on the recordings.

We are not talking about jamming, period.

I take it that none of the members of this infinitely subtle and world wide intelligence network, or any of their friends, has yet seen fit to spread a rumor of a physically plausible causal mechanism by which this disturbance may have occurred.

PBL

PBL

I am glad to see forget chip in with some experience. A decade ago I was chatting about Elaine Scarry's proposal that TWA 800 might have been brought down by stray radiation from a nearby P3 with a colleague of mine in the Physics department. He supposed that it all depended on how well-cooked the U.S. Navy likes its airplane crews.

People have said all kinds of silly things on this thread and this may be one. Check the picture earlier on this thread (or some other) of the box in which the EEC sits on the engine. A better Faraday cage you will not see, unless it's an airplane hull.

Please also note, as bsieker and others have repeatedly pointed out, that any purported EM explosion left no visible traces in a highly-instrumented system!

Engineers who deal with electromagnetic radiation have spent most of their education learning how to stop the bits they work on being influenced by EM radiation from bits other people have worked on (or the sun, or more recently the background radiation from the earth and from cosmic rays). It's been like that now for, dare I say it, over a century. It didn't start with the invention of cell phones!

Please see forget's next post for a link to an EM test cell operated by QinetiQ. Note (a) how big the kit is, and (b) how close to the aircraft it must be to get suitable field strengths. Take it seven hundred feet away (the altitude of the purportedly affected aircraft) and it is going to have to be at least 50 times the power of what you see in the brochure, which amongst other things means a lot larger.

I believe some sort of EM interference testing of this sort is a requirement for aircraft certification, but I can't actually put my hands on either the requirements or on any B777 EM testing history at the moment.

PBL

forget

For those with no idea of the electronic hammering aircraft are subjected to as part of RF Immunity Certification a commercial test facility may be of interest. Note that these very expensive, and very large kits are to prove aircraft immunity. So, to produce something even bigger, but highly mobile, capable of breaking through that immunity, is waaaay beyond the wit of most. In fact, I'd say it was impossible.

See HERE

airfoilmod

If your vacuum is controlled by Infrared, like your Television, the maid may easily change your viewing pleasure. The Theory, as I see it, isn't about motors and static, but relays, slaves, (solenoids), and CONTROLS. Also, Radio seems to be the sole player in this one-up EMF discussion. As fragile as some postulated theories seem, no less fragile is a proffered indignant defense. It's all interesting, but to me getting defensive is annoying.

Would you be more engaged if this were re: Airbus? It has a computer "in the Loop". Introducing microamperage into 28vDC and with attendant interfaces is quite a project. Beyond my ken anyway. I'd be disappointed if this were moved to Tech, lomapaseo and Greendot along with Chris Scott get way over my head as it is. Feel a whole lot more like Watson than Holmes.

I prefer the Microwave Tx approach, more powerful and versatile. Where are the Relays for the Spar Valves? How close to the composite flooring are they? For that matter, how close to each other are they? Fuel seems to be the direct cause, the rest of the story is yet to be written I'd say.
As an aside, can any theorist connect the forward cargo hold Fire Bottle UA fiasco to Control/Interference issues-Surprising "fleetwide attention" is always interesting.

FullWings

Maybe someone with engineering schematics could comment but I was under the impression that the 777 spar valve sensing system has three states, i.e. Open, Closed and In Transit. If this is true, then a record would have been left of any malfunction and it would have been picked up quite early on by Rolls/Boeing/the AAIB, etc. As this doesn't seem to be the case, maybe the cause lies elsewhere?

airfoilmod

The failure happened very late in the recording cycle. What happened (if anything) could have gone unrecorded or corrupted by the signal folks are discussing. (Relative to FDR). Recorded or not, Flight Record isn't available to those outside, precious little Data from the chaps. Gawrsh, there's no film in the camera, Syl.

lomapaseo

No reason to be cycnical. If the data was corrupted or missing the AAIB would have stated as such in their releases. Also I haven't heard a thing about mysterious on-board happenings to such things as the Pa's, passenger mobiles, etc. or other consumer goods found in the cabin. One would have thought that at the very minimum all the address books and hard drives in these passenger electronics would have been the first to go.

Sunfish

It's only a rumour from lloyd's and it is rumour I couldn't work out how it's possible either....but that's the current rumour.

As for physics and impossibility.... my brand new Motorola Razr3 has come back to life after an accidental dipping in salt water!

snanceki

What is surprising to me is the FACT that the AAIB have failed to issue an updated statement for some time now.

This suggests that they really don't know what happened or alternatively they do but consider the chances of a repeat event to be EXTREMELY low.

There appears to be consensus that the engines were partially starved of fuel almost simultaneously.

So what are the most likely causes.
1. Spar / engine valves PARTLY closed.
2. Inadequate fuel in the wing tanks.
3. Inappropriate fuel.

1. Spar valves partly closed.
Possibility of some form of EMI (airborne) or power spike (wiring), likely emanating from adjacent systems on board.
However I would expect that the spar valve and engine cut off valve position to appear on the DFDR (due to importance of these devices on engine performance).
In which case this possibility is easily verified or discounted.
If indeed this valve was only partly open I would have expected the finding to be published even if the cause was still undetermined due to the significance of the event and the possibility of a repeat due to an unknown mechanism.

2. Inadequate fuel in the wing tanks.
Mechanism suggested (failure of scavenge system from CWT to wing tanks (due to temp/design/sensing) but the problem here is why the fuel level system did not warn (or subsequently record on the DFDR) that the wing tanks were empty. The AAIB stated that sufficient fuel was indicated as being on board.
Both engines experiencing the same problem within 8 secs is troubling since differences in engine fuel consumption and initial wing tank level / tank capacity are unlikely to be exactly the same. However this could be accounted for by the significant attitude change of the aircraft during finals.

3. Inappropriate fuel. The -57 C freezing point spec of the fuel taken post the event is interesting. Why was the spec so "good" and could this be linked to pump cavitation? Incorrect fuel would have impacted other aircraft unless the combination of fuel and engine type didn't mix well but why did the problem occur at the end of the flight rather than take off etc when the engines are under greatest stress.

I don't discount any of the possibilities but IMHO the faulty fuel monitoring system (incorrect calibration?) appears marginally the most plausible.

I suspect that the AAIB must be struggling even with the wealth of data around them or more likely confident that this really was a 1 in X million aircraft specific event, otherwise I would have expected an updated report by now.

Guess we will have to be patient!

PBL

You shouldn't be surprised. It is standard procedure. ICAO conventions require a preliminary report within 30 days and a final report, and that is what most accident investigation agencies do, AAIB included. It is very rare for any information to be made public in between, except when safety issues are identified in the course of an investigation, in which case safety recommendations dealing with these issues may be issued.

There are very good reasons for this. If you publicise what you are *thinking about*, then all those people and organisations who feel they might be disadvantaged by your potential conclusions will activate their lobbying machines to try to get your ideas changed. This happened most notoriously during the AA587 investigation, and prompted a public reprimand to the involved parties from the NSTB Chairman.

This suggests only that the AAIB are holding to their normal procedures during investigations.

BTW, trying to come up with a list of all possibilities and reasoning about them is a very good exercise. It is one of the skills that I try to encourage students to develop in my course on causal explanation. It is a skill that requires considerable experience and practice, as well as apparently (dare one say it) a certain amount of analytical talent. (In mathematical terms, one would speak of devising a *partition of the space* of possibilities, "space" here meaning simply "set".) The main trick is not only to make sure you have included everything, but also to learn to apply some self-checks to see if you indeed have everything. The trick which comes a close second is to devise a partition that is explanatorily fruitful, that is, in which each category leads you down some relatively narrow set of possibilities. The third trick is to know when you don't have enough information to be able effectively to apply tricks 1 and 2.

I don't know how you judge the likelihood of your three "likely causes", but I think it is obvious to both you and me that this is by no means a complete enumeration of the possibilities at any level of generality. So I am not sure how it helps anyone.

PBL

snanceki

Hi,
Thanks for your reply.
The key difference on this investigation is that we have an almost intact aircraft rather than wreckage spread over a wide area / difficult terrain.

So either the cause is already known and the paperwork is just being completed or something very strange occurred. The absence of actions (couple of exceptions) to other aircraft of the type/fleet is also interesting suggesting it is aircraft specific.

My list was of course not exhaustive and all the "debate" on the subject has been undertaken with very few facts.

However, with the wealth of interest and the various "theories" that have been put forward by individuals with diverse backgrounds I still remain surprised that the AAIB has remained as tight lipped as they have on this occasion.

Of course doing so is good practice but the very nature of this event when combined with the fact that the aircraft remains largely undamaged I remain surprised that there has been some further interim statement.

Just a personal observation that may or maynot be indicative of something.
OK. It doesn't add anything specific but does anything else put forward on this site?

As I said we will have to be patient. Only then will we be able to draw conclusions and see whether any of the theories put forward prove to be anywhere near (by chance) correct.

HotDog

Snanceki,

Doesn't surprise me one bit. Forty pages of repetitive nonsense by armchair "experts" has proven to be absolutely useless to the AAIB and like you say, wait for the official result of the investigation.

PBL

I don't agree. I grant you it has been repetitive, but I have read some extremely sophisticated analyses of fuel physics and chemistry which no one can reasonably regard as "nonsense". As well as some interesting facts about EMI in fuel subsystems on other aircraft. We have also produced a Causal Control Flow Diagram of the EEC environment for RR-powered B777's, which as far as I know does not exist elsewhere, as well as a fuel pathway diagram which is available to anyone who wants it. Neither of these are nonsense; they are, to the contrary, useful, even essential, analysis tools.

I understand certain people may not be interested by any of this, but then one wonders why they would even be reading this thread.

PBL

slip and turn

Well I am not surprised but I am slightly annoyed that the AAIB has not released much information publicly about the cause.

As for the insurance angle, because large wodges of their cash are involved, it is often worth heeding 'medium-matured' rumours in the London Insurance market, and if any significant part of that market are settling on radio interference as one cause (it's the third that get's you, right?) then at this stage of the game I would heed it, because later on, if any element of it is true, I would expect it to have been sanitised for the annuls.

To lend context to my thoughts, I am currently reading Peter Wright's "Spycatcher" after somehow having previously failed to open it.

In the book I haven't come across airfoilmod's elusive word "tramp signal" yet, but Peter Wright was a practical electronics expert (a government bugger!) and his book is the kind of place I'd expect to find a word like that used to discuss some kind of feedback phenomenum perhaps, which he might have learned how to exploit 50 years ago - so goodness knows what's possible in SIGINT / problematical to civvie circuit designers in 2008 ... I predict that the state of both these arts will be for a time reconciled in the circuitry of the new Airbus military tankers (select customers only)

HotDog

PBL, none of those high tech hypotheses that you are referring to are of any use unless they pinpoint and prove the cause and effect of the subject. I agree there have been some sophisticated discussion put forward on fuel physics and chemistry which would be better placed in the Flight Testing forum.

PBL

Granted. I just enjoy reading the contributions of people who know so much more than I do about a subject which is relevant, even though I have no idea at this point whether any of it is causal to the accident. I also really don't care that much where such discussion takes place, although I understand that others might have preferences.

PBL