BA 777 landing accident at LHR

[Evan]

Does anyone yet know if and why this phenomena is confined to Trent powered 777's, and what Boeing and/or RR has changed in the design?

Does anyone know why this phenomena has occurred only once in one 777 and only in one aircraft fueled from the same source that day? The conditions listed in the finding have all been repeated without incident many, many times. I would expect an inherent design weakness issue to reoccur at least transiently. One can call it a rare anomaly, except that here it happened in two autonomous engine fuel/oil heat exchangers at almost the same instant. All they had in common within the scope of this finding was the fuel system design, the fuel supply and the atmospheric conditions, yet none of these were unique to the incident aircraft that day. My logical mind still has trouble with this explanation.

[snanceki]

Why just the Trent?

The Trent has a lower specific fuel consumption vs GE which most probably equates to lower fuel flow speeds in the pipework.
This combined with low demand due to idle thrust during decent, low fuel temps etc?
Looks as though nobody recognised the potential for this type of fuel system icing and I expect new homologation tests will have been developed to ensure fluid dynamics and thermodynamic heat balance in the fuel system meet new requirements...for ALL aircraft.
Stuart

[Highkeas]

Does anyone yet know if and why this phenomena is confined to Trent powered 777's, and what Boeing and/or RR has changed in the design?

Does anyone know why this phenomena has occurred only once in one 777 and only in one aircraft fueled from the same source that day? The conditions listed in the finding have all been repeated without incident many, many times. I would expect an inherent design weakness issue to reoccur at least transiently. One can call it a rare anomaly, except that here it happened in two autonomous engine fuel/oil heat exchangers at almost the same instant. All they had in common within the scope of this finding was the fuel system design, the fuel supply and the atmospheric conditions, yet none of these were unique to the incident aircraft that day. My logical mind still has trouble with this explanation.

Research subsequent to the 777 crash found that shutdown of one engine for unknown reasons happened on several 777s with this engine but icing may not have been suspected (you can research this yourself for more information - I probably read about it in AW&ST magazine). Update: two incidents involving iceing of fuel, including a 777, are noted on page 122 of the AAIB report.
It probably pure chance that it happened on both engines within 7 seconds of each other (as I recall). I deal with statistics all the time and statical outliers (something like an 5-sigma event or 1 in 3,000,000) happen occasionally. These events are the bane of failure investigations because they are so difficult to duplicate.

The AAIB report is here:

http://www.aaib.gov.uk/cms_resources.cfm?file=/1-2010%20G-YMMM.pdf

[Cargo Runner]

My logical mind still has trouble with this explanation.

I still have problems with this ice theory and I still stick to my original theory which has little to do with the plane but more the surroundings and happenings of the day at LHR.

[SYDCBRWOD]

I still have problems with this ice theory and I still stick to my original theory which has little to do with the plane but more the surroundings and happenings of the day at LHR.

I don't have any issues with the findings. As to why Both engines cut out within a few seconds of each other despite being independent systems - I profer this:

Both used the same fuel. Both systems probably contained equal volume (so equal effects). Both systems were exposed to the same environmental contitions. Both engines would have had equal thrust settings applied at all phases of flight. Given these similarities, I can understand why the ice formation would have occurred nearly similtaneously, and why when the pilots advanced the throttles the resulting suction drew the ice to block the screens at roughly the same time.

Experiment time... Load 6 cans of soft drink into the freezer - pull two out after 2 hours, then at 2.5 and 3 hours. At one of those stages ice you'd find that the soft drinks would have become slushies - both of them. If one had not frozen and the other had then that would support your theory or they had been a different temps when put into the freezer.

PS - remember to pull the remaining soft drink cans out of the fridge when you have discovered the 'slushie' stage - otherwise you will find the "wife very angry from the exploded softie can" stage.

Cargo runner - remind me of your theory? Was in the proximity to Tony Blair's motorcade? If this motorcade was emitting some form of EM blocking signal - presumably to stop the detonation of remote IED's - why wouldn't this same device mess with every car on the road (every car these days is computer controlled)?

[EconomyClass]

Wow can you transmit waves that interfere with car computers? That sounds like a heck of a toy for juvenile delinquents.

[Highkeas]

Wow can you transmit waves that interfere with car computers? That sounds like a heck of a toy for juvenile delinquents.

There is a description in this report of jamming devices used by VIPs:

http://www.un.org/News/dh/docs/mehlisreport/pdf/mehlisreport.pdf

See page 38, paragraphs 148 & 149.
They are used mainly to jam cell phones and hand held radios which can be used to detonate IEDs.

[Alpha Sierra]

Could the crew have done any more?

Here's an interesting account of the accident and the options available to the flight crew by David Learmount over at Flightglobal:

http://www.flightglobal.com/blogs/learmount/2010/02/at-720ft-above-ground-level.html

[old timer]

Here's an interesting account of the accident and the options available to the flight crew by David Learmount over at Flightglobal:

http://www.flightglobal.com/blogs/le...und-level.html

It was good argument by all , however i found it worrying to accept the fact that nothing could have been done by flight crew (totaly defensive)
Another point is the moisture in the fuel tanks as suggested by some that could cause the ice build up and my question is why there should be water in the fuel tanks despite the fact it is a requirement to drain and sump water from the fuel tank during the over night stop by the Main. Team ??
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[Highkeas]

............. my question is why there should be water in the fuel tanks .............................

Good question.
When the tanks are filled on the ground the excess space contains air at the ground level temperature and relative humidity. During flight this air cools down and when the dew point is reached water condenses out of the air and into the fuel.

[old timer]

Good question.
When the tanks are filled on the ground the excess space contains air at the ground level temperature and relative humidity. During flight this air cools down and when the dew point is reached water condenses out of the air and into the fuel.

This is the reason why water sump and drain is a requirement when the Acft on ground for more than 4 hrs (H2O is heavier than jet A1 and get collected at the lowest point of each fuel tank.)

[mawheatley]

This is the reason why water sump and drain is a requirement when the Acft on ground for more than 4 hrs (H2O is heavier than jet A1 and get collected at the lowest point of each fuel tank.)

Well when the aircraft was on the ground it wasn't cold enough for the moisture to condense out of the air that was in the fuel tanks. Therefore the moisture particles were held in suspension in the air. As the fuel was pumped in it naturally went below that air. Now move forward to the cruise phase, and the crew were saying it was some of the coldest air they'd flown through. Here the air is no longer capable of holding that moisture - as Highkeas said, it was below the dew point, the temperature at which the moisture starts to condense out. Only at this point does it become water, which like you say is denser than Jet A1, and so sink to the bottom of the tank. Water sump and drain on the ground would not have eliminated the water because at that point it was not in its liquid state.

[TeeVee]

so, an aircraft as advanced as the 777 doesn't have a fuel-water separator like every damn diesel truck? you have got to be kidding me!

[old timer]

Well when the aircraft was on the ground it wasn't cold enough for the moisture to condense out of the air that was in the fuel tanks. Therefore the moisture particles were held in suspension in the air. As the fuel was pumped in it naturally went below that air. Now move forward to the cruise phase, and the crew were saying it was some of the coldest air they'd flown through. Here the air is no longer capable of holding that moisture - as Highkeas said, it was below the dew point, the temperature at which the moisture starts to condense out. Only at this point does it become water, which like you say is denser than Jet A1, and so sink to the bottom of the tank. Water sump and drain on the ground would not have eliminated the water because at that point it was not in its liquid state.

this is why water drain/ sump from the fuel tanks is required per the Acft MANIF. MPD and the airline MIP which states : water sump need to be performed every in service checks (normally every 36-48 hrs) after being on ground for certain period of time to allow the water to be collected from the bottom of tanks. so repeating such MAINT task will prevent moisture accum and induced in the engine fuel sys

Another point and correct me if i am wrong : all modern jet engines have fuel / oil cooler which cools the oil and heat the fuel, and I am confident that the RR ENG has the same , but i could be wrong

in case of icing, this should trigger the delta P sw at the fuel filter which will cause the caution msg (fuel LO PX) at this stage the fuel should by-pass the filter.

B.R