Narrative:

The accident occurred during engine start after pushback from the stand. 
After the right generator came online an electrical failure occurred in the 
right main bus. The failure resulted in severe internal arcing and short circuits 
inside the two main power contactors of the right main bus. The heat generated 
during the failure resulted in the contactor casings becoming compromised, 
causing molten metal droplets to fall down onto the insulation blankets below. 
The insulation blankets ignited and a fire spread underneath a floor panel to 
the opposite electrical panel (P205), causing heat and fire damage to structure, 
cooling ducts and wiring. The flight crew responded to the bus failure and a 
burning smell by shutting down the right engine and taxiing to a nearby stand. 
The Airfield Fire Service attended the aircraft when it arrived on stand and 
entered the Main Equipment Centre where they discovered significant smoke 
but no fire. The passengers were evacuated uneventfully via steps.

CAUSAL FACTORS:

1. An internal failure of the Right Generator Circuit Breaker or Right Bus Tie Breaker 
contactor on the P200 power panel inside the Main Equipment Centre resulted in 
severe internal arcing and short-circuits which melted the contactor casings. 
The root cause of contactor failure could not be determined.
2. The open base of the P200 power panel allowed molten metal droplets from 
the failed contactors to drop down onto the insulation blankets and ignite them.
3. The aircraft’s electrical protection system was not designed to detect and 
rapidly remove power from a contactor suffering from severe internal arcing and 
short-circuits.
4. The contactors had internal design features that probably contributed to the 
uncontained failures.

The investigation identified the following probable causal factors that led to the 
fuel flow restrictions:

1) Accreted ice from within the fuel system released, causing a restriction 
to the engine fuel flow at the face of the FOHE, on both of the engines.
2) Ice had formed within the fuel system, from water that occurred naturally 
in the fuel, whilst the aircraft operated with low fuel flows over a long period 
and the localised fuel temperatures were in an area described as the ‘sticky range’.
3) The FOHE, although compliant with the applicable certification requirements, 
was shown to be susceptible to restriction when presented with soft ice in a 
high concentration, with a fuel temperature that is below -10°C and a fuel flow 
above flight idle.
4) Certification requirements, with which the aircraft and engine fuel systems 
had to comply, did not take account of this phenomenon as the risk was 
unrecognised at that time.

Narrative:

A Boeing 777-266ER, SU-GBP, sustained substantial damage in a cockpit 
fire at Cairo International Airport (CAI), Egypt.
The aircraft was preparing for departure at Gate F7, Terminal 3 at Cairo 
Airport at the time the crew detected a fire at the right hand lower portion 
of the cockpit area, below the number 3 window. The crew and passengers 
expeditiously deplaned with no injuries. 

Examination of the aircraft determined that the cockpit was extensively damaged, 
and two holes were burned through the aircraft external skin just below the First 
Officer’s window. In addition, smoke damage occurred throughout the aircraft, 
and heat damage was found on overhead structures well aft of the cockpit. 
The crew oxygen system has a number of oxygen lines and hoses running 
through the area were the fire started. Some of those hoses are electrically 
conductive, according to research. The investigators are conducting tests to 
determine if a failure involving these hoses could have been the primary cause 
of the fire.

Currently, the Boeing Company, in coordination with the investigation and the 
Federal Aviation Administration of the United States, is working to develop 
mitigation strategies that are designed to eliminate this potential source of 
fire in the cockpit. Boeing is working to finalize a Service Bulletin that is 
designed to inspect for and eliminate potential electrical faults around the 
crew oxygen system lines and hoses. In addition, Boeing is developing plans 
to replace the current crew oxygen system hoses with new, non-conductive 
hoses and is evaluating the benefits to providing additional electrical grounding 
points for crew oxygen system components.

CONCLUSIONS:

Examination of the aircraft revealed that the fire originated near the first officer's 
oxygen mask supply tubing, which is located underneath the side console below 
the no. 3 right hand flight deck window. Oxygen from the flight crew oxygen system 
is suspected to have contributed to the fire's intensity and speed.
The cause of the fire could not be conclusively determined. It is not yet known 
whether the oxygen system breach occurred first, providing a flammable environment 
or whether the oxygen system breach occurred as a result of the fire.

Accident could be related to the following probable causes:

1. Electrical fault or short circuit resulted in electrical heating of flexible hoses in the flight 
crew oxygen system. (Electrical Short Circuits: contact between aircraft wiring and oxygen 
system components may be possible if multiple wire clamps are missing or fractured or if 
wires are incorrectly installed).
2. Exposure to Electrical Current