Arcniz
From an ETOPS perspective, I think some folks have a hard time entertaining how both engines could respond similarly to a single or series of faults. The timing isn't so exclusive of what appears to be reality. There is a "range" of possibilities that could easily have trapped both Powerplants in a "simultaneous" cycle of failure. Subtle changes, or commands, or even trimming, result in subtle responses from the A/C. Large inputs can create their own problems.
Possible: BA038, established in flight, is exposed to fierce low temps.
There is some amount of Water in the Fuel, in some "state".
On descent, Equilibrium is established, the "system" is constant
Engines have established stasis, low operating temp. sipping fuel
1. At low altitude (~800feet) the Autothrottles command significantly increased thrust.
2. The engines respond, accelerate, and make commanded power.
3. Everything impacting the new thrust level is instantly at high level
4. Fuel flows rapidly increase, as does temperature in the engines
5. Stasis collapses, Fault (s) appear and overwhelm the system.
Possible: The isolation of the powerplants from each other works to prevent simultaneous failure, but given a demand in the nature of a sudden command for full power, the scale of the demand can "override" functional isolation. What I'm trying to say, is that though the Fuel was contained in separate tanks, it was of the same make-up, exposed to very similar conditions, and could have easily created unrecoverable circumstances in two engines within 8 seconds.
Back to stasis. The profile of the descent and the extended period of low power and uncommonly cold and perhaps contaminated Fuel created a homogeneous environment for the final hole in the cheese. I think the restriction was closer to the HP pumps than spar valves, LP stand pipes, or system piping upstream from the pylons and heat exchangers. The instantly present Vibration and fuel demand, including sonic energy and increased temp. may have served to melt/dislodge pack up the heat exchangers with the ice crystals that may have collected prior to throttle up. Within 8 seconds of either engine? Possible.
Airfoil