1.71.5.204-B20160823
The 777 that limped into Heathrow has been confirmed a hull-loss,the first 777 since it took to the skies.

This is what I caught from a pilot-forum so far "with the help of my friends":

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At about 700 ft AGL, the auto throttle commanded engine acceleration. One engine started to rollback during and the other engine started to
accelerate then 8-10 seconds later began to roll back. Once the flight
crew noticed, they pushed the throttles up and the engines' EECs
responded but the engines did not. It appears that no fuel was getting
to the engines.

The investigation continues to look broadly for a cause of the dual
engine rollbacks. Fuel exhaustion is the only item that has been
positively ruled out. Aspects that the FAA believes the investigation
is concentrating on are:

o Ice in the fuel somehow limiting the fuel flow to the engines. A
maintenance message indicating excessive water in the center tank was
set during taxi on the two previous flight legs, although it cleared
itself both times. The airplane was being operated in a high humidity,
cold environment, conducive to ice formation.

o Small-sized contamination building up in the engine fuel systems
somehow limited the fuel flow to engine. All the fuel samples have
ested for contamination of larger particles (sizes outside the fuel pecification). Testing has been started looking for small particles
greater than 5 microns).

o Engine hardware failures sending inaccurate data to the engine
electronic control (EEC) causing the EEC to demand insufficient fuel.
A preliminary review of the EEC data from the right engine shows
erratic combustor inlet pressure (P30). A leaking P30 sense line could
cause this, or the EEC receiving a higher than actual fuel flow parameter.

o Software coding problem in the EEC causing the EEC to demand
insufficient fuel. British Airways installed a new engine EEC software
revision in December 2007. The software was approved in May 2006. There
were several changes to the software as part of the revision. Two items
seem remotely related to the accident: improvements to low power stall
recovery logic and fan keep out zones for ground maintenance. The first
two items would be related to a part 25 compliance issue, while the last
two items would be related to a part 33 compliance issue.

As stated yesterday in this briefing paper, the electrical system anomalies noted earlier have been resolved, as describe below, and the conclusion now
is that the electrical buses were powered until impact and performing as expected.

o The auxiliary power unit (APU) began its auto start sequence, even
hough the buses were still powered. In the days following the event,
the flight crew has added additional details to their report. The crew
now believes they turned the APU on prior to impact. There was sufficient
time before the impact for the APU inlet door to open, but not for the
APU fuel pump to turn on or the APU engine to start spooling up.

o The quick access recorder (QAR) saved data and shut down approximately
45 seconds prior to impact. The QAR saves data in batches. It is believed
the QAR was working properly and was in the process of saving data when
impact occurred, accounting for the "lost" 45 seconds of data.

o The fuel crossfeed valves were closed in flight according to the flight
crew, but the switches were found in the open position and only one valve
was open. In the days following the event, the flight crew has added
additional details to their report. The crew now believes they opened the
alves just prior to impact and the airplane lost power before both valves
moved to the open position.

o The ram air turbine (RAT) was found deployed, even though the buses
were still powered. It did not deploy until after the airplane came to
a stop, as determined by the pristine condition of the turbine blades.
The RAT either deployed due to electrical power loss during impact with
a failed air/ground signal or the impact unlatched the RAT door.

Fuel system: Leads regarding water in the fuel and fuel contamination are continuing to be investigated. Fuel testing looking for small-sized contaminants (5 microns) is beginning. The tanks are still being drained
and the team hopes to start evaluating the fuel system hardware tomorrow.

Engines: Component testing and teardown of the engine-driven fuel pumps
and the fuel metering units is planned for later this week. The data from
the electronic engine controls is still being analyzed. Rolls-Royce is
planning an engine test, unscheduled as yet, to try and duplicate the rollbacks.

Crashworthiness: Cabin crew and passenger questionnaires indicate that the evacuation bell was faint, but the evacuation light was seen and the captain's message to evacuate over the passenger address system was heard. Preliminary data indicates that the descent rate at impact was roughly 30 ft/sec. Dynamic seat requirements that became effective at the introduction of the Model 777 series airplanes require seats protect occupants for hard landing impact up to 35 ft/sec. The passenger with the broken leg was sitting next to the point where the right main landing gear punctured the fuselage and pushed into the cabin.

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