fdr

Hi there.

The B777 is designed to initiate an automatic re ignition if a flame out occurred where no ignition was already on, but as the engines were still above idle (no ENGINE THRUST alert to crew) during the initial phase of the approach, this is a moot point. Once the configuration for landing was initiated, continuous ignition is applied.

If an icing related event had occurred at the intake of the FP due to pressure drop or otherwise (other restrictions that may have existed in the system) then the interruption of fuel to the engine would have been temporary, the engine driven fuel pump has suction feed capability at low altitudes/thrust levels, and reignition would have occurred.

The dynamics of the event require that some thrust remained from the engines, at least in the latter phases of flight.

In respect to the isolated development of software, the design constraints and group backgrounds/experience and training will tend to develop similar solutions in isolation. The engineers natural tendency for frugality in memory overhead certainly comes to mind, as does the limited inputs available and the specific task output constraints as drivers towards similar solutions.

Personally, I remain concerned in respect to the number of the B777's that have opted to have single TAT probes fitted vs the option for dual probes. I have had on another Boeing 4 holer all engines rollback to idle at rotate (while in HOLD mode...) as the TAT probe had failed and driven the EPR limit to near idle. This is not the case with the BA aircraft, but remains a potential vulnerability to the pilot.

Interesting discussion.

regards

caiozink

It now appears the fuel composition might be an issue.....high content of waxy substances and very low temperatures....

RomeoTangoFoxtrotMike

Appears from where, exactly ??

glad rag

Reference please.

amc890

I have also heard a whisper that an announcement is due soon. Sorry no sources or references though (and I know pics or it didn't happen)

chris weston

No attribution and so extreme care needed ....and (i) we were told categorically that the fuel was within indeed exceeded spec and (ii) doubtless we shall get the "but it's after the Olympics now" brigade out soon.

Yes I've read every post.

CW

lomapaseo

Even some of the better ones like mine in Jet Blast

Viking101

So when is the official report of the accident coming out?

Lets have some experts from the NTSB (or eq in UK) stating the problem, although I am bearing in mind all your tech knowledge and interesting speculations and rumours

Feels it has been too long now... Someone trying to hide anything maybe? Or just hoping that people "forget" about the whole thing? Yay- more speculations

PETTIFOGGER

For Viking 101
I have no idea when the AAIB will issue another interim report, or a substantive report. You may wish to bear the following in mind when considering the time-scale for the issue of a further report.
Fluid mechanics is one of the most demanding disciplines in physics.
AFAIK, fuel systems for all aircraft are designed using Newtonian-fluid mechanics principles, since aviation fuel is a “Newtonian fluid”. If however a fuel becomes ‘waxy’, its properties and transport may (only ‘may’) then be governed by “Non Newtonian” fluid mechanics. Checking the modelling of the fuel flow design against Euler and Navier-Stokes equations, analysing Computational Fluid Dynamics data for both Newtonian and non-Newtonian fluids is not a quick job and will probably need to be run many times with different temperature and fuel viscosity regimes. So we wait.
Rgds.

cwatters

It's not unusual for final reports to take more than a year. The latest formal reports page on the AAIB site here.. Air Accidents Investigation: Formal reports
lists 4 reports from accidents in 2006 and 2 reports from 2005. None from events in 2007 yet.

Last report I read suggested the manufacturer was building possibly complex test rigs to simulate conditions so not surprised that takes time.

Green-dot

In any investigation like this, in order to find the facts and the reasons why, the time it takes to reach a conclusion is of secondary importance.

We do not control the day, the day is controlling us . . . . .

Green-dot

HarryMann

A Professional Forum like this is really no place for puerile conspiracy theories... please desist.

RomeoTangoFoxtrotMike

If you had been paying attention, you would have seen posts 852 and 1006, where I note:-

"I've just crunched the data on published formal reports by the AAIB back to 2006... The average length of time from incident to final report publication is 25.6 months, i.e. a little over two years. This does not and has not stopped them issuing recommendations, where appropriate, before the final report."

Viking101

Hairy man, take it easy with your choice of words! I might get offended I dont think I have been the only one with theories... How many posts are put into this thread? Thought so. Maybe you want to "desist"?

RTFM, I am sorry I did not read your post- most illuminating! Thanks for the constructive info!

Pettifogger- Excellent

beamender99

Wall Street jounal says

U.S. and European air-safety regulators, concerned about potentially dangerous ice buildups in the fuel systems of certain long-distance jetliners, are about to issue new operating rules for around 220 Boeing 777 aircraft, according to people familiar with the matter.
The mandatory safety directives apply only to planes with engines manufactured by Rolls-Royce PLC, which account for about one-third of the ...( I have not subscribed to read further )


ITN lunchtime says report is out later today.

Reporter suggests that the report says fuel OK but believed report will say ice formed in fuel lines.

Reuters item today

(Reuters) - U.S. and European air-safety regulators, concerned by potentially dangerous ice build-ups in the fuel systems of some long-haul jets, will issue new operating rules for about 220 Boeing (BA.N: Quote, Profile, Research, Stock Buzz) 777 planes, people familiar with the matter told the Wall Street Journal.
The mandatory safety directives apply only to planes with engines manufactured by Rolls-Royce PLC, which comprise about a third of the Boeing 777 fleet world-wide.
But under prodding from British officials, Boeing will analyze whether similar precautionary measures should be extended to the rest of its 777 line, people familiar with the matter told the WSJ.
The rules are expected to be released in the next few days.

pubsman

AAIB has announced issue of Interim report today:

Air Accidents Investigation: Interim Report - Boeing 777-236ER, G-YMMM

shoey1976

BBC COPY:
The British Airways Boeing 777 that crashed at Heathrow in January was PROBABLY brought down by ice in its fuel system according to the latest findings of a report by the Air Accident Investigation Branch.
The pilots of the plane managed to get it down safely, and 136 passengers and 16 crew escaped without serious injury.
The AAIB now believes the flow of fuel dropped shortly before the engines on the plane lost power -- at 720 feet above ground, less than a minute before touchdown and that ice could have clogged the fuel system.
But the investigators say they still don't know how the ice could have formed. Water is naturally present in aviation fuel -- the investigators believe there may have been around 5 litres within this aircraft's fuel load. But the report says levels of water recovered the fuel after the crash were very low for a Boeing 777.
They dismiss the suggestion that the fuel itself froze or became 'waxy' as icing occurred.
The interim report says the plane flew through unusually cold air over Siberia while en route from Bejing to Heathrow. The fuel temperature fell to minus 34 degrees centigrade. But jet fuel should not freeze until it is at less than minus 57 degrees centigrade, and the report says the temperatures involved were not "unique".
The investigation into the crash of flight BA038 continues with testing at Rolls Royce in Derby, and Seattle in the US, home of Boeing.
Water in aviation fuel can be dissolved at the molecular level, or simply float as free water, suspended in the fuel. As the fuel gets colder tiny droplets can form and freeze.
The mystery facing investigators is why this might have happened on an apparantly fully-functioning aircraft.
Water in the fuel is controlled by draining it regularly out of the fuel tanks -- and on the Boeing 777 a so-called 'scavange system' pumps it out.
Ice can form when the fuel temperature drops to around -1 to -3 degrees centigrade. Generally the ice crystals simply float and drift in the fuel without causing harm.
Only when the temperature falls further does the ice stick together. Within the fuel system a heat exchanger is used to increase the fuel temperature, but its possible the blockage might have occurred before this point.
The investigation team have build a test rig and introduced pre-prepared ice into the fuel system to see if it would clog up. But the amounts they had to put in to make this happen were far greater than is normal.
Despite that the scenarios being considered by the AAIB are based on the idea that the ice formed gradually in the system and was released as the plane prepared for landing.
But the report makes three safety recommendations -- that the US Federal Aviation Administration and the European Aviation Safety Agency introduce interim measures to reduce the risk of ice forming on the Boeing 777 powered by Trent 800 engines.
The other recommendations are that the agencies should consider the implications for other aircraft types, and review the requirements for new engines.
This accident remains an enormous for the investigation team. But their reported stresses the rareness of this crash.
"The accident flight was unique", it says, "in that this has been the only recorded case of a restricted fuel flow affecting the engine performance to the extent of causing HP pump cavitation" - the damage found within the pumps that alerted the investigators to the loss of fuel pressure.
The report goes on: "this is the first such event in 6.5 million glihht hours and places the probability of the failure as being 'remote'."

philipat

I am very late to this thread as a result of receiving the below link. I don't have time to read all the way back through the thread, with no disrespect intended.
I assume that this item has been thoroughly disected and probably dismissed in the thread and I would be grateful if someone could kindly refer me back to the definitive post#.


BA038 - The Truth About Flight BA038

Carnage Matey!

Your linked page gave me a laugh. I've not read so much idiotic nonsense for some time now!

philipat

Carnage Matey:

Yes I know. I just wondered if earlier Posts had reached any conclusions as to who might go to such trouble to produce a professional looking web page. Competitor Airline or ex-wife?!!