Posted by
ChristiaanJ, ref. post #1782:
Somebody, many hundreds of posts ago, suggested that, with water being heavier than fuel, under the circumstances a lot of water could already have drained from the aircraft by the time the fuel samples were taken.
Question: might there have been a lot more water than quoted in the AAIB report?
Please read the report(s) again.
AAIB interim report G-YMMM, Page 2, second column:
"The aircraft had previously operated a flight on 14 january 2008 from Heathrow to Shanghai, with the return flight arriving on 15 January 2008. The aircraft was on the ground at Heathrow
for 20 hours before departure to Beijing on 16 January 2008."
AAIB interim report G-YMMM, Page 13, first and second column:
"G-YMMM was last sumped at Heathrow on 15 January 2008 prior to the flight to beijing. The aircraft had also been sumped at London heathrow whilst on maintenance, on 14 January 2008."
"Prior to the accident the operator had initiated a review of the effectiveness of their [water] sumping programme, . . . . . ., a number of aircraft were checked in a warm hangar where any ice in the fuel tanks would have melted and migrated to the drains. G-YMMM was sumped in this manner on 14 December 2007. The review established that whilst the free water does freeze and could occasionally block the tank drains, there was no evidence of any significant quantities of free water having accumulated in any of the 43 Boeing 777 aircraft."
AAIB Special Bulletin S1/2008, first column, Page 5:
"The aircraft's [G-YMMM] fuel tanks were last checked for water in the fuel on the 15t January 2008,
this was prior to it's refuelling for the outboard sector to Beijing."
With the aircraft on the ground for 20 hours and a review programme in place, wouldn't it be logical that sumping on 15 january took place at a time it was estimated that any ice in the tanks had melted before sumping commenced? Especially with the aircraft on the ground
for 20 hours and temperatures well above freezing (as records of those dates indicate) and sumping taking place before refuelling. The interim report does not mention how many hours after arrival from Shanghai water sumping was performed but to my knowledge this is done immediately prior to refuelling? Refuelling probably took place any time after the payload, flight planning and weather for the flight to Beijing were known, so this would have happened perhaps only a few hours (but still on 15 January?) before departure?
If so, and water sumping was done correctly, there would be very little water in the tanks. This, together with sumping on 14 january during maintenance should imply the tanks were virtually free of water as G-YMMM departed to Beijing.
After reading the report several times, although it is very informative, new questions regarding the aircraft systems and engines surfaced for me which i shall digest for a while.
The emphasis is now focussed on ice. 5 liters of water diluted in approx. 100.000 liters of fuel . . . . and a lot of data mining.
I'm sure they will find the facts, the evidence, and the reasons why in the near future. I hope they are not barking up the wrong tree.
The investigation, although very detailed and thorough, gives me the impression of trying to castrate a fly with boxing gloves on
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