BA 777 @ LHR

[Hypersonic]

Hi All.

You all appear to be bored with this one. A month since the last post!

pprune have concluded that the amount of fuel in the wing tanks was compatible with the AAIB reported INDICATED level, using frost patterns on the wing.
Seems a reasonable conclusion to me.
So this reduces the possibilities further.
Despite noise to the contrary EMI appears to be climbing the list.

Your latest thoughts, knowledge on this one or are you still at a loss?

Stuart

[Gabriel]

I still don't see EMI ikely att all.
Because the software and the hardware did what they should have done: When the thrust levers went forward the fuel mettering valves opened to their full open positions and remained there.

[Dmmoore]

Hi All.

You all appear to be bored with this one. A month since the last post!

pprune have concluded that the amount of fuel in the wing tanks was compatible with the AAIB reported INDICATED level, using frost patterns on the wing.
Seems a reasonable conclusion to me.
So this reduces the possibilities further.
Despite noise to the contrary EMI appears to be climbing the list.

Your latest thoughts, knowledge on this one or are you still at a loss?

Stuart

Yes. EMI would be a possibility if the systems didn't operate properly. It's been reported that they did.

The only thing that will prevent a jet engine from accelerating (assuming no compressor stall) is lack of fuel. Some how fuel didn't reach the burner nozzles.

[flyboy2548m]

Some how fuel didn't reach the burner nozzles.

Let's see you reach them nozzles when you ain't even in the tanks. Yeah-yeah, I know the "indications were this and such", too bad I don't give a flying f*** what the indications were, the result speaks waaay too loudly.

[Dmmoore]

We are on the same page Flyboy2548M.
The only thing I will allow is the remote possibility of something preventing the fuel from entering the fuel delivery system.
These include"
Four intakes blocked 80% or better at the same time. How?

What ever liquid there was in the tank wasn't Jet fuel. It would have to be a lighter element that does not burn well and floats on and does not mix with fuel. How did it get there? Why can't any trace be found?

The tanks did not have a sufficient quantity of fuel to supply the engine fuel delivery system.

DUH!

[Peminu]

Being such a big aircraft, I doubt that throttle is controlled by wires (not even from the cockpit to the hydraulic controls/valves).

My (very parlor style) bet:

1) Low voltage producing a situation where valves/controls are not responding immediately to the input (cabin crew was using all the power while using the speakers at highest volume to give landing instructions to passengers, while turning lights on, coffee heating started at the same time, and 6 bathrooms were flushed simultaneously as well).

or

2) Has somebody checked the "plastic" cover over the electric bus cables? Hummm...I think I heard of a recent event similar to this one where bathroom dripping (or probably Per not aiming correctly to the target) produced a wetting over some important cables.

[Gabriel]

Being such a big aircraft, I doubt that throttle is controlled by wires (not even from the cockpit to the hydraulic controls/valves).

My (very parlor style) bet:

1) Low voltage producing a situation where valves/controls are not responding immediately to the input (cabin crew was using all the power while using the speakers at highest volume to give landing instructions to passengers, while turning lights on, coffee heating started at the same time, and 6 bathrooms were flushed simultaneously as well).

or

2) Has somebody checked the "plastic" cover over the electric bus cables? Hummm...I think I heard of a recent event similar to this one where bathroom dripping (or probably Per not aiming correctly to the target) produced a wetting over some important cables.

The software and the hardware did what they should have done: When the thrust levers went forward the fuel metering valves opened to their full open positions and remained there.

To make it clearer, the throttle is hardware, the fuel metering valve is hardware, and between them there is the FADEC with its software.
The FADEC:
1) detected the throttles being moved forward,
2) commanded the fuel metering valves to open, and
3) received feedback from the fuel metering valves confirming that they actually opened.
For some reason whatsoever, the opening of the fuel metering valve did not result in an increase of power as commanded (or in fact it did result at first but then the engines reduced power by themselves while the fuel metering valve kept opening more and more until reaching its full open position).

Here is an over-simplified and probaly wrong sketch of the fuel system, or of what I understood it was like from reading posts in Internet forums!

Fuel.gif (2.79 KiB) Viewed 8017 times

Once the fuel metering valve is open, there are not so many ways to prevent the fuel from getting to the engine. Either the pumps are not working, or the pipping is blocked, or there is no fuel.

[Peminu]

To make it clearer, the throttle is hardware, the fuel metering valve is hardware, and between them there is the FADEC with its software.
The FADEC:
1) detected the throttles being moved forward,
2) commanded the fuel metering valves to open, and
3) received feedback from the fuel metering valves confirming that they actually opened.
For some reason whatsoever, the opening of the fuel metering valve did not result in an increase of power as commanded (or in fact it did result at first but then the engines reduced power by themselves while the fuel metering valve kept opening more and more until reaching its full open position).

Here is an over-simplified and probaly wrong sketch of the fuel system, or of what I understood it was like from reading posts in Internet forums!

Fuel.gif

Once the fuel metering valve is open, there are not so many ways to prevent the fuel from getting to the engine. Either the pumps are not working, or the pipping is blocked, or there is no fuel.

Nice and simple diagram. But still, I can see a problem if we have a false signal (value on the other extreme) or wrong signal (value different than real) that the valve is open (the arrow going up in the diagram between the fuel metering valve and the fadec). What seems to me weak about this theory is that we are talking of 2 valves (one for each engine). In this case, the failure could be in the "reference point" or "zero point" or "maximum point" used to compare the signal received from the valves. This may be due to wrong voltages, short circuits, grounding wires, EMI or other reasons. So I still wouldn't discard this as a posibility, and add it to the 3 you mentioned (pumps. piping or lack of fuel).

[Dmmoore]

Nice and simple diagram. But still, I can see a problem if we have a false signal (value on the other extreme) or wrong signal (value different than real) that the valve is open (the arrow going up in the diagram between the fuel metering valve and the fadec). What seems to me weak about this theory is that we are talking of 2 valves (one for each engine). In this case, the failure could be in the "reference point" or "zero point" or "maximum point" used to compare the signal received from the valves. This may be due to wrong voltages, short circuits, grounding wires, EMI or other reasons. So I still wouldn't discard this as a posibility, and add it to the 3 you mentioned (pumps. piping or lack of fuel).

You need to read the entire thread to understand that your point has been discussed and the following items resulted:
1. Did FEDAC respond to the pilots command to increase power? Answer, Yes.
2. Did the fuel control unit (mounted on the engine) respond to the request? Answer, Yes.
3. Did the engine respond to the request for more power? Answer, Yes, at first then engine power reduced.

Flight recorders confirm the the engine control system was working correctly. A jet engines power output is directly related to the quantity of fuel thrown into the burner section. More fuel, more thrust. For some reason the quantity of fuel entering the burner section decreased and the throttle system didn't command the decrease. All valves were set as commanded by the throttle system. Therefore the engines had to provide increasing thrust "IF" the fuel were available.

[Peminu]

Nice and simple diagram. But still, I can see a problem if we have a false signal (value on the other extreme) or wrong signal (value different than real) that the valve is open (the arrow going up in the diagram between the fuel metering valve and the fadec). What seems to me weak about this theory is that we are talking of 2 valves (one for each engine). In this case, the failure could be in the "reference point" or "zero point" or "maximum point" used to compare the signal received from the valves. This may be due to wrong voltages, short circuits, grounding wires, EMI or other reasons. So I still wouldn't discard this as a posibility, and add it to the 3 you mentioned (pumps. piping or lack of fuel).

You need to read the entire thread to understand that your point has been discussed and the following items resulted:
1. Did FEDAC respond to the pilots command to increase power? Answer, Yes.
2. Did the fuel control unit (mounted on the engine) respond to the request? Answer, Yes.
3. Did the engine respond to the request for more power? Answer, Yes, at first then engine power reduced.

Flight recorders confirm the the engine control system was working correctly. A jet engines power output is directly related to the quantity of fuel thrown into the burner section. More fuel, more thrust. For some reason the quantity of fuel entering the burner section decreased and the throttle system didn't command the decrease. All valves were set as commanded by the throttle system. Therefore the engines had to provide increasing thrust "IF" the fuel were available.

I understand your point Don.

But there is an important issue here: we are talking about 2 engines.

In cases of fuel starvation (for the little I know), always one engine gives problem before the other (even if it is just for a few seconds). Apparently, in this case it didn't happen that way, and both motors behaved identically and simultaneously.

Is for this reasons that I would check again and again on common elements for both engines, that include power supplies (electricity, hydraulics, etc.), electronics, software, control signals (big issue because this can fool not just the engine system, but also the data recorders), etc.

[AndyToop]

I understand your point Don.

But there is an important issue here: we are talking about 2 engines.

In cases of fuel starvation (for the little I know), always one engine gives problem before the other (even if it is just for a few seconds). Apparently, in this case it didn't happen that way, and both motors behaved identically and simultaneously.

Is for this reasons that I would check again and again on common elements for both engines, that include power supplies (electricity, hydraulics, etc.), electronics, software, control signals (big issue because this can fool not just the engine system, but also the data recorders), etc.

I'm afraid you are wrong again, have you read the report? It is linked earlier in the thread, but it says

The engines initially responded but, at a height of about 720 ft, the thrust of the right engine reduced. Some seven seconds later, the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

[Half Bottle]

On this point how common is it, upon fuel exhaustion, for both engines to continue to produce thrust (above flight idle, but below commanded) as opposed to just flaming out? We're talking about a minute or so of the engines operating under this condition if I remember the timeline correctly, aren't we?

I am biased in favor of the fuel exhaustion theory, but I keep getting hung up on the fact that those engines kept running at reduced power.

[Dummy Pilot]

I am biased in favor of the fuel exhaustion theory, but I keep getting hung up on the fact that those engines kept running at reduced power.

In response to your post, I was going to say that there may not be a lot of data on what happens in fuel exhaustion situations because it just doesn't happen that often......however, I suddenly thought of several instances including Air Canada, Air Transat, United, and Avianca #52 whose NTSB report is HERE. A quick check of the Avianca report shows that the engines flamed out literally within seconds of each other which kind of surprises me. However, the fact that Avianca and BA both occured in the approach phase may be important if you believe that fuel exhaustion played a role. The higher nose attitudes that are inherent in the approach phase would have a negative affect on fuel feed with low amounts in the tank (in fact, the Avianca crew was aware enough to brief the "'Low Fuel Missed Approach" procedure which attempts to keep the boost pumps covered). If you are trying to maintain a glide path, either manually or on autopilot, and you start to lose thrust, you would naturally increased the nose angle to try to keep the glideslope which would only worsen a low fuel situation.

(For what it's worth, I'm not sure I buy the fuel exhaustion angle, but something might be gained by looking at the reports for Air Canada-Gimli, Air Transat-Azores, United-Portland, etc)

[Peminu]

I'm afraid you are wrong again, have you read the report? It is linked earlier in the thread, but it says

The engines initially responded but, at a height of about 720 ft, the thrust of the right engine reduced. Some seven seconds later, the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

Sorry Andy (and Don) because I was lost a long time between AD.com and being rescued by AD.info for many days.

The thread started there and I just was trying to remember it.

The first entrance on this thread have a link to "official" preliminary reports, but I tried to click there and they are no longer available.

In any case, I am getting out of arguments.

Here is a new one: the "Antartic iceberg" situation,

Everybody is talking about water-fuel contamination. But solid water (ice) behaves different than liquid water.

Ice will still (I believe) have a bigger density than jet fuel. So, if ice forms, will go to the bottom of the tank.

Because of high altitude weather conditions, this block sticks to the surface (bottom) of the wing (outside temperatures very low).

Then, after descent, the wing gets heated and the ice slides and block the pump intakes.

After the crash, ice melts and disappears (separated from the fuel, so everybody thinks that there was no water in the fuel).

Please don't tell me that somebody else already said that and was prooved wrong, because then I would only be left with the "frozen carburator theory" ).

Anyway, thanks to you, Don and everybody for your patience and anwers.

[Dmmoore]

When the aircraft was refueled and if the fuel was contaminated with water, the water would be in a liquid state. In the liquid state it would be sloshing around on the bottom of the tanks until the fuel chilled.

In the mean time the engines have been started and the water would be sucked into engines and water would flame the engines out. The aircraft would be towed back to the gate and all aircraft refueled at the airport would be grounded until they were shown to be free of water.

Simply put, if water were the issue, it would have manifested it's self long before the aircraft reached altitudes and temperatures where the water would turn to ice.

No aircraft refueled at the departure point encountered any fuel problems.

[Dmmoore]

On this point how common is it, upon fuel exhaustion, for both engines to continue to produce thrust (above flight idle, but below commanded) as opposed to just flaming out? We're talking about a minute or so of the engines operating under this condition if I remember the timeline correctly, aren't we?

I am biased in favor of the fuel exhaustion theory, but I keep getting hung up on the fact that those engines kept running at reduced power.

The fuel line feeding the engine in your car is about 3/8" (12 MM) in diameter. The fuel line in the 777 is about 4". When your car runs out of fuel, the engine usually stumbled for a few seconds before it finally quits running.

When the tank runs dry, the pumps begin to cavitate (suck air) and fuel pressure drops but does not stay at zero until the pumps will no longer puck up any fuel. This can process can take several minutes when defueling the aircraft and I suspect it's similar when drawing fuel from the tank to an engine. It depends on the amount of air mixed with the fuel.

The engines operating at high power will suck an almost empty dry very quickly. At idle it may take several minutes.

[AndyToop]

Hey Peminu,

maybe the links I remember were to newspaper articles which quoted the report.

Here is a link to the AAIB website, where you can get a PDF version of their latest report on the incident.

[Half Bottle]

The engines operating at high power will suck an almost empty dry very quickly. At idle it may take several minutes.

That makes sense, but throttle (if not the engines) were set to high power for the last minute or so of flight, yes? Do you mean that if a low fuel condition was encountered when the engines were intially idled that the pumps would start cavitating and then, at that point, it just didn't matter what the commanded fuel flow was?

Or do you mean that even a minute of high throttle setting isn't going to necessarily suck the tank completely dry?


Either way, I see your point.

[Hypersonic]

So consensus supports lack of useable fuel but to the best of my knowledge nobody has yet put forward a feasible failure mode to support this contention.

So as I believe Don stated somewhere a long time ago something is wrong with the data we have been presented with or at least assumed.

With so many creative minds putting forward "possible" scenarios and most of these being "shot down" this is becoming ever more interesting.

IMHO the most worrying aspect is that unlike with many other"accidents" this aircraft is largely intact so any suspect components have been able to be tested to ensure compliance with spec. Two engines just don't quit or choose to run below commanded power by chance.
A reason exists so what have we potentially overlooked?

In order to understand the fuel pick up system from the WING tanks I should like to ask the following.

As I understand it there are two pick up points per tank. Correct?
Are they positioned front / rear or inboard / outboard?
If the LP boost pump fails I understand that the system will still deliver fuel to the engine HP pumps "by gravity".
I don't understand "by gravity" unless we mean by syphon, since the fuel first has to go up (into pickup) before it goes down (to engines).
I am also interested in how air is prevented from entering the pickup should one of the pickups become uncovered (above fuel level) due to aircraft attitude and the relatively "flat" nature of the tanks. Syphon effect would be broken if any air gets into system.

Finally, I'm interested in some aspects of the spar valves.
Although these are designed as On/Off valves is it conceivable that they could by some unknown mechanism that motored and stopped at an intermediate point? Presumably they are not spring loaded Open since they are required to stay closed in the event of a crash when potentially no power is available.
Is spar valve position/signal recorded on the DFDR?
Are these valves controlled by some form of power relay which in turn is operated by some common, or at least in very close proximity, wiring.
Where are the relays sited?
Are these relays in close proximity to one another in the fuselage or wing mounted.
What conditions cause the valves to close. Just the fire handle switches?

Basically I'm trying to understand whether either of the above systems might hold the key.

I await your (vast) knowledge on these systems.

[Dmmoore]

So consensus supports lack of useable fuel but to the best of my knowledge nobody has yet put forward a feasible failure mode to support this contention.

Yes I have but it's buried in the mass of the thread. To summarize:
A miss calibration of the fuel quantity system could lead to fuel exhaustion.

So as I believe Don stated somewhere a long time ago something is wrong with the data we have been presented with or at least assumed.

I did. If the data we have been given is flawed, so are all assumptions derived from the data.

Two engines just don't quit or choose to run below commanded power by chance.
A reason exists so what have we potentially overlooked?

In order to understand the fuel pick up system from the WING tanks I should like to ask the following.

As I understand it there are two pick up points per tank. Correct?

Correct.

Are they positioned front / rear or inboard / outboard?

The wing and center tanks have one inlet for each electric boost pump. There are two pumps in each tank directly feeding the engines. In the center tank, both pick ups are aft, center. The fuel in the center tank is used in climb / cruise and would be empty during descent so no forward pick up is necessary. The wing tank pick ups are both inboard, one forward, one aft.

If the LP boost pump fails I understand that the system will still deliver fuel to the engine HP pumps "by gravity".
I don't understand "by gravity" unless we mean by syphon, since the fuel first has to go up (into pickup) before it goes down (to engines).

It's not really gravity but suction from the main engine pump that removes the fuel in the event both electric boost pumps become inop. However, they never did become "INOP" so all of the speculation below is not relevant.

I am also interested in how air is prevented from entering the pickup should one of the pickups become uncovered (above fuel level) due to aircraft attitude and the relatively "flat" nature of the tanks. Syphon effect would be broken if any air gets into system.

Finally, I'm interested in some aspects of the spar valves.
Although these are designed as On/Off valves is it conceivable that they could by some unknown mechanism that motored and stopped at an intermediate point? Presumably they are not spring loaded Open since they are required to stay closed in the event of a crash when potentially no power is available.
Is spar valve position/signal recorded on the DFDR?

The position of the spar valve is recorded.
They are powered from the emergency battery bus. They are motor driven "Gate" valves that remain at the last position selected. They can be opened only by operating the fuel on/off switch. When wired correctly, they can be commanded closed through the fire wall shut off switch or the fuel on / off switch. This aircraft was mis-wired so the fire wall shut off feature was inop.

Are these valves controlled by some form of power relay which in turn is operated by some common, or at least in very close proximity, wiring.
Where are the relays sited?
Are these relays in close proximity to one another in the fuselage or wing mounted.
What conditions cause the valves to close. Just the fire handle switches?

No power relay is involved. The valves were not part of any fuel restriction.

Basically I'm trying to understand whether either of the above systems might hold the key.

I await your (vast) knowledge on these systems.[/quote]

[Dmmoore]

The engines operating at high power will suck an almost empty dry very quickly. At idle it may take several minutes.

That makes sense, but throttle (if not the engines) were set to high power for the last minute or so of flight, yes?    Do you mean that if a low fuel condition was encountered when the engines were intially idled that the pumps would start cavitating and then, at that point, it just didn't matter what the commanded fuel flow was?Or do you mean that even a minute of high throttle setting isn't going to necessarily suck the tank completely dry?Either way, I see your point.

To clarify if others have questions. When the engine are operating at high power, the fuel flowing through the fuel feed system is high thus emptying the tank at a higher rate. When the tank runs dry, the reduction in fuel flow immediately affects the engines power output. At low power, the pumps may be delivering air and fuel mixed but the fuel delivered meets or exceeds the fuel needed to provide the low power setting. If opening the throttle increases the fuel demand above the available supply, the engine will not respond to the throttle position but will provide the power the available fuel flow allows. In this case the throttle is not controlling the engines power out put.

[Peminu]

Hey Peminu,

maybe the links I remember were to newspaper articles which quoted the report.

Here is a link to the AAIB website, where you can get a PDF version of their latest report on the incident.

Thanks Andy for the reference.

I would like to put some parts that I consider specially important of this report (not with the idea of rejecting or discarding opinions expressed here, but because I consider them interesting and maybe contradictory):

...The total fuel on board was
indicating 10,500 kg, which was distributed almost
equally between the left and right main fuel tanks, with
a minor imbalance of about 300 kg. The fuel cross-feed
valves indicated that they were closed and they had not
been operated during the flight. ...at a height of approximately
780 ft, in accordance with the briefed procedure, and
shortly afterwards the autothrottles commanded an
increase in thrust from both engines. The engines
initially responded but, at a height of about 720 ft,
the thrust of the right engine reduced. Some seven
seconds later, the thrust reduced on the left engine to a
similar level. The engines did not shut down and both
engines continued to produce thrust at an engine speed
above flight idle, but less than the commanded thrust.
The engines failed to respond to further demands for
increased thrust from the autothrottles, and subsequent
movement of the thrust levers fully forward by the
flight crew...

...The aircraft came to rest on the
paved surface in the undershoot area of Runway 27L.
A significant amount of fuel leaked from the aircraft
after it came to rest, but there was no fire...

Weather
The recorded weather at Beijing, prior to departure,
indicated no significant weather and a surface temperature
of -7ºC...

...The ambient temperature at FL348 was approximately -65ºC and
the associated total air temperature (TAT) was -37ºC.
Shortly after crossing the Ural mountains, the aircraft
climbed to FL380. There was a region of particularly
cold air, with ambient temperatures as low as -76ºC...

..The lowest TAT recorded during
the flight was ‑45ºC, and the minimum recorded fuel
temperature was -34ºC. The fuel temperature in flight
must not reduce to a temperature colder than at least
3ºC above the fuel freezing point of the fuel being used.
The specified freezing point for Jet A-1 fuel is -47ºC;
analysis of fuel samples taken after the accident showed
the fuel onboard the aircraft had an actual freezing point
of -57ºC...

...the fuel metering valves on both engines correctly moved to the
fully open position to schedule an increase in fuel flow.
Both fuel metering units were tested and examined, and
revealed no pre-existing defects.
Both engine low pressure fuel filters were clean. The fuel
oil heat exchangers (FOHE) in both engines were free
of blockage. The right FOHE was clear of any debris,
however the left engine FOHE had some small items of
debris on its fuel inlet bulkhead. The high pressure filters
were clean. The variable stator vane controllers and the
fuel burners were examined and found to be satisfactory.
Detailed examination of both the left and right engine
high pressure fuel pumps revealed signs of abnormal
cavitation on the pressure-side bearings and the outlet
ports. This could be indicative of either a restriction in
the fuel supply to the pumps or excessive aeration of
the fuel. The manufacturer assessed both pumps as still
being capable of delivering full fuel flow...

...Initial results confirm that the
fuel conforms to Jet A-1 specifications and that there
were no signs of contamination or unusual levels of water
content...

...The fuel boost pumps, and their associated low pressure
switches, were tested and examined and found to be
satisfactory. A pressure and suction test of the engine
fuel feed manifold, from the fuel boost pumps to the
engine, did not reveal any significant defects. Similarly,
a visual examination of the fuel feed lines, using a
boroscope, did not reveal any defects or restrictions...

...On examination, both of the engine spar valves were
found to be OPEN, allowing the fuel leak evident at the
accident site...


So, if fuel starvation is the most probable theory (agree with Don's expertise), I guess that the problem is that part where they say that the tanks leaked fuel after the crash, and have them (investigators) doubting that a (possible bad) reading of the fuel left in the tanks was correct. Probably this fuel leaked was a small amount that couldn't be sucked by the pumps (cavitation marks convince me that there was no fuel. I guess that Don can lighten me on the probability that this cavitation marks were from a previous flight).

[Hypersonic]

So reiterating. Don suspects inadequate fueal due to an instrument calibration issue.

OK but this doesn't sit comfortably with "significant quantity of fuel leaked after the crash". If indeed the tanks were (almost) empty from a useable fuel point of view the open spar gate valves wouldn't have allowed fuel to leak since "suction" was not available from the HP pumps post crash, so no leakage would occur. i.e. unuseable fuel would have been "trapped" within the wing tanks.

If indeed the fuel level was above the minimum useable level then fuel starvation wouldn't fit either.

UNLESS maybe "significant amount" equates to the difference in minimum useable fuel level that occurs due to aircraft attitude change.

Anybody got any idea how much difference we are talking about" Approach angle vs angle on ground post crash (u/c damaged).

If indeed Don is correct (I'm sure he will be!) the cause of the potential mis calibration can potentially impact other aircraft of the type. So why no requirement for a check to be made on other aircraft? Presumably this wouldn't be a difficult task?

Comments?

[Dmmoore]

First, lets define what a "significant amount" is. How was it determined to be a "significant amount?" "IF it was from the smell of fuel, 10 liters smells the same as 1000 liters in the right environment. The ground under the engines (where the majority of the "significant amount" was noted) was wet with rain water. Ten or so liters could cover a large area simply because of the fuel spreading on top of the dampness.
Second, considering the AAIB, NTSB, Boeing and RR have not released any significant operator letters on the subject we can assume for the moment that what ever the cause, the AAIB, NTSB, Boeing and RR think the cause is unique to this aircraft.
"IF" a miss-calibrated fuel quantity system turns out to be the or is part of the problem, that event would be limited to BA's training and not an event that needs to be sent to all operators as a warning. The correct fuel calibration procedure is detailed in the AMM.

[David Hilditch]

Second, considering the AAIB, NTSB, Boeing and GE have not released any significant operator letters on the subject we can assume for the moment that what ever the cause, the AAIB, NTSB, Boeing and GE think the cause is......

Minor point, the accident aircraft had Rolls-Royce Trents.