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AAIB BA38 B777 Initial Report Update 23 January 2008

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AAIB BA38 B777 Initial Report Update 23 January 2008

Old 1st Feb 2008, 08:45
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Remaining fuel upon arrival?

"Recorded data indicates that an adequate fuel quantity was on board the aircraft"

I do not support the theory, PADHIST brings forward.

But in any case, what was the exact amount of remaining fuel? - anybody knows?

"adequate" is a rather vague statement.

On the B-767 there is a max. pitch angle (I believe 20 degrees) in case of a go-around with low fuel state - no limit for flapssetting and pitch angle for approach. And as far as I remember, fuel x-feed should be selected to ON. B-777?
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Old 1st Feb 2008, 08:51
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As with all Boeing courses the essence is "need to know" and that applied on our B777 course with regard to the fuel system.

The normal operation with wing and centre fuel was to operate with all the pumps on. Due to the centre producing higher pressure than the wing pumps the centre would empty first (necessary for wing bending moments etc), then with around 900kgs left in the centre the pumps would become uncovered in the tank and the pump switch pressure lights would illuminate plus EICAS messages.

Centre pumps then switched off and EICAS messages obviously disappeared.The fuel feed would then transfer to the wing tanks (tank to engine, pumps already running) and would (assuming no imbalance, which was a very infrequent occurrence) remain so for the rest of the flight.

However we were never told where in the tank these centre pumps were but, one can assume they must not have been in the lowest point (cruising attitude) as 900 kgs still remained in the tanks. This last 900kgs was then transferred to the wing tanks (without any pilot intervention) by "other" pumps. No display of this part of the system on the schematic and obviously as it was automatic not included in the " need to know".

The "leaked" report talks of "water" maintenance messages in the centre tank, again something the crew were not party to (need to know) but where in the centre tank would this "water" have collected? At the lowest point?

If so, it would have still been there when the tank stopped feeding and subsequently have been pumped into the wings.

No suggestions, just facts on how the fuel system works....
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Old 1st Feb 2008, 09:24
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woodpecker

from my post 235:

On the B-767 there is a max. pitch angle (I believe 20 degrees) in case of a go-around with low fuel state - no limit for flapssetting and pitch angle for approach. And as far as I remember, fuel x-feed should be selected to ON. B-777?

Do you have figures for the 777?
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Old 1st Feb 2008, 10:08
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If so, it would have still been there when the tank stopped feeding and subsequently have been pumped into the wings.

No suggestions, just facts on how the fuel system works....
Woodpecker... there are "facts".. and then there are "insufficient facts".

On the 777, there are jet pumps for scavenging fuel and there are jet pumps for scavenging water.

The pickup points for the jet pumps for water are at the very lowest point in the tanks and pick up small quantities of water throughout the flight and mix this with fuel to be burnt in the engines. In these small quantities, they present no problem to the engine (who knows.. it may even improve the performance of the engine???).

The jet pumps for fuel are in the centre tank and help get rid of the 900kgs in the Centre Tank. These do not begin operating until the fuel in the wing tanks goes below a certain level (c/o a system of valves and floats).

This type of system has been operating very well on all Boeing aircraft for, literally, many decades.

The ultrasonic water detectors fitted to the 777 have trigger points of 31.8 and 627 litres per wing/centre tank respectively. Clearly, there would have to be an enormous amount of water to even be of concern to the 777.

Note: this data is from the Boeing Maintenance Manual which may differ from the pilot's manuals from time to time.
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Old 1st Feb 2008, 10:18
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Pinkman:

It takes an hour or so to run some ASTM tests and in all the so-called 'leaks' I havent heard one say "we have analysed both the fuel from the aircraft tanks which were supplying at the time as well as the retention samples from lab, terminal, and hydrant/bowser and have discounted fuel contamination as the cause of the incident". Its the easiest, quickest, and cheapest theory to dismiss. So dismiss it!


I am sure that is not going to happen at the moment for a number of reasons:

The AAIB folks will not be wanting to drip feed information into the public forum.

A confirmation of fuel meeting specification (remembering that it will have been Chinese No3 fuel, but that meets checklist, and I think has slightly better cold flow properties), will direct all the tabloids into a witch hunt about RRís engine management systems, Boeingís fuel system design on the 777, BAís operating procedures, LHRís ATC procedures, and heaven knows what else, to say nothing of the pilotsí lifestyles, and other irrelevancies.

If there is any suspicion that the fuel did not meet checklist, then there is the very delicate matter of achieving the co-operation of the Chinese Authorities in following up the causes and ensuring that there are no further occurrences. Any such discussions will test the diplomatic skills of the AAIB and the ARB. No supplying Company likes to admit that their product failed to meet specification, and I can imagine that any suggestion to a Chinese parastatal of a quality issue initially will be rebuffed, the more so at a time when the authorities are putting in considerable effort to ensure the best possible face of China as a full member of the world community for the Games later this year. And donít think that managing loss of Ďfaceí is just an Oriental problem: itís a requirement in the West too, itís just that we donít call it that.
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Old 1st Feb 2008, 10:28
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Iam qualified to test aviation fuel to its freeze point and i would be surprised to see if this is the cause of the crash. I have an idea who is testing the fuel from the crash etc.
There are additives in aviation fuel that can limit fuel freezing, but wont remove the water if present. As pointed out previous, small amounts of water are not always a drama, its the fact that water freezes that is.
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Old 1st Feb 2008, 10:47
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With all the talk about water in the fuel tanks, waxing and icing the AAIB report states that the engines were running, therefore some fuel was being pumped to the engines. It is hard to imagine that an equal fuel restriction would have physically occurred (almost) simultaneously on both engines when more thrust was demanded, especially as the report states that recorded data (FDR?) indicated adequate fuel.
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Old 1st Feb 2008, 12:07
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If there was waxing in the tank I am sure it would have given some very strange readings very early on and the management system would have moved the fuel if a problem was seen.
Negative. The roundtrip time for a sound wave from the emitter to top of the fuel and back to the receiver isn't going to change with the matter state of the fuel.
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Old 1st Feb 2008, 20:10
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Well having flown BA777s and MM and also had the guys as my copilots, sometimes odd things happened to the displays. On venturing into the cabin there was always someone using a laptop. I've been retired a while now so will leave it to the pprune experts, but my first thought on hearing the news was that cellphones or laptops were suspects. Maybe not, but also maybe not lots of other things posted here too.
I think that we are all concerned that the AAIB may never actually get to the bottom of it.
I wish they would hurry up, then we could all get some sleep!
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Old 1st Feb 2008, 20:24
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Fuel sample retention

It has been asserted that fuel samples would be retained at the bowser or hydrant. Does anyone know if that is SOP at PKG? It certainly isn't where I work - fuel samples are retained for each batch of fuel, not each refuel.
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Old 1st Feb 2008, 20:42
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ChristiaanJ

You are probably right. But none of us know what happened. Nothing can be discounted yet. The engines were getting fuel, but not enough. Thats all that we know here.
I keep thinking that it could have been me in the left seat and I am in no doubt that I am not alone.
I wonder what I would have done? I hope that my crew and I would also have made the grass.
Something denied the engines the fuel they needed. BOTH ENGINES...it's really incredible, or at least beyond ten to the minus nine.
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Old 1st Feb 2008, 20:52
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Loose rivets,

I'm not discounting anything like that either... I was just saying that we are talking about a one-in-a-million event, so the typical cellphone and laptop no longer qualify.

I've done EMC testing.... and at times it was more difficult to stop the box from radiating too much EMI itself, rather than keeping the EMI out....
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Old 1st Feb 2008, 22:02
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Just suppose for one minute it was Gordon's cavalcade and jammer. Do you think they would ever tell us? Would be like saying to Osama "here's a new easy way to wreak havoc"

Last edited by stickyb; 2nd Feb 2008 at 03:24. Reason: sp
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Old 1st Feb 2008, 22:32
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Folks, if you have the expertise to log on to PPrune, you have the skill necessary to <i>buy</i> a cell phone jammer.

But what the heck does this have to do with the discussion at hand?
Either the thing was on board, at which point you'd have to ask: why would someone turn it on right at finals? Frankly, there's no reason that makes sense, given the other, more "sporting" opportunities that would have presented themselves before hand. On the other hand, if you want to argue for RFI, there are plenty of ordinary cell phones out there, and one in a million could -- perhaps under the influence of the right combination of overuse and tight jeans -- perform in an unpredictable and noxious manner on the wiring a few centimeters away.

Or the thing was in the environment, several miles from the threshold, and on the ground, and then you'd have to ask, "Why does this matter again?" I mean, have you driven by an airport and measured the environmental RF noise? You have more cellphones, more bluetooth devices in one area, along with several radar systems and HF/VHF/UHF transmitters, and most of these have a clear line-of-sight to the runways. Heck, I remember being in a bus passing a military airport in Syria where the noise was so bad, the entertainment system speakers started serenading us -- and they were switched off!

So, no. I don't see cell phone jammers as an issue. RFI is a "dark horse" candidate, but there's no call to get exotic here.
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Old 1st Feb 2008, 22:47
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DingerX,
Thanks, we're obviously on the same wavelength.
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Old 1st Feb 2008, 23:07
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Clee mentions the possibility of a "cellphone disrupter" used by the military as a possible cause of the crash.

I am a ex grenadier guardsman and we used these devices when performing changing of the guard. if you have ever watched this event, when marching from wellington barracks to Buckingham palace you might notice one of the guys wearing a big box on his back, with a cover to match the tunic, well thats what they are. they were originally brought in to combat the threat of the IRA detonating roadside bombs when the guard change marched between the barracks and the palace, and at their most vulnerable. Anyone remember the horse guards killed in the same manner near hyde park some years ago?.

I do recall at the time (and this is some years ago!!) that they would play havoc with some car centeral locking systems and car alarms to our amusement!!, but these devices have come a long way in terms of technology in the last 15 years. They do have limited range and certainley dont have the capability to bring down a aircraft.
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Old 1st Feb 2008, 23:19
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Hughesyd,

That big black box on his back must cause havoc with his reproduction equipment - and to his immediate neighbours.
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Old 2nd Feb 2008, 00:35
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External interference

Quote from DingerX:
Or the thing was in the environment, several miles from the threshold, and on the ground, and then you'd have to ask, "Why does this matter again?" I mean, have you driven by an airport and measured the environmental RF noise? You have more cellphones, more bluetooth devices in one area, along with several radar systems and HF/VHF/UHF transmitters, and most of these have a clear line-of-sight to the runways. Heck, I remember being in a bus passing a military airport in Syria where the noise was so bad, the entertainment system speakers started serenading us -- and they were switched off!
(Unquote)

So, while we are exploring this remote posibility of external RFI (or whatever we are going to call it), I wonder if you experts might like to address the specific proposal of what might be capable of doing the business from a range of about 200 - 800 metres.

As it's the early hours, I'm going to indulge my imagination for a few moments, knowing nothing of the subject. Seems to me, the transmission would have to be (a) unusually high power and (b) directional (unlike most of the examples above).

High power from a domestic or mobile power-source would imply split-second pulses; due partly to the constraints of the power source, but also to avoid cooking the antenna?

Directional transmission would require a fairly complex antenna, I presume. This would be bulky and cumbersome to aim at a moving target. But you don't have to move it, because every A/C approaching the duty runway will be at exactly the same height and position as it passes, say, the 2-mile point on the ILS.

That just leaves the problems of choosing the most effective frequency or frequencies (to penetrate shielding, and have a sufficiently adverse effect), and finding/creating the transmitter and antenna. The latter would need to fit in the loft space of an ordinary semi-detached house.

When you have considered this - purely hypothetical - proposal, can you tell us why it couldn't work?
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Old 2nd Feb 2008, 09:51
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ETOPS

And the type still has ETOPs approval.
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Old 2nd Feb 2008, 10:08
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Virtual Reality - your first point is wrong, which means the rest of your train of logic is flawed. Even if the aircraft was on 'minimum fuel', reserves for a 777 are typically only about 3 tonnes. If flying around above minimum reserve fuel leads to this sort of accident then I think Boeing are in big trouble.

Somebody mentioned excessive water warnings in the fuel tanks. I know BA have been checking all the 777 tanks for water. They are getting lots of warning messages but not finding any water. The problem is the unreliable water sensors, not actual water in the tanks.
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