Data, downloaded from the Electronic Engine Controllers
(EECs) and the QAR, revealed no anomalies with the
control system operation. At the point when the right
engine began to lose thrust the data indicated that the
right engine EEC responded correctly to a reduction
in fuel flow to the right engine, followed by a similar
response from the left EEC when fuel flow to the left
engine diminished. Data also revealed that 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.
This would seem to suggest that the correct signals were getting through to both engines and the engines were trying to respond accordingly. Apparently no other as yet significant defects have been found.
Does this therefore narrow down the possible cause to a momentary absence of liquid Jet A1 under pressure at the burners?
I am totally speculating here, but given that air temperatures were lower than Jet A1 freeze temperature, and even though the tank temperature never got to critical levels according to instrumentation, would it be possible for a deposit (perhaps like cardiac plaque in arteries) of wax or frozen fuel to form somewhere in the fuel pipework?
As it warmed such a plaque could let go, blocking a filter and perhaps giving an engine the mechanical equivalent of a heart attack?
Of course that idea stretches credibility because it had to happen to both engines within seven seconds of each other, there was no EICAS message about clogged filters and it may be physically impossible to put a skin of frozen wax on the inside of a pipe thats carrying -34C jet A1.
No more speculation from me till the next official report.