Egyptair B772 at Cairo on Jul 29th 2011, cockpit fire
Last Update: November 29, 2012 / 17:01:43 GMT/Zulu time
Probable causes for the accident can be reached through:
- Accurate and thorough reviewing of the factual information and the analysis sections
- Excluding the irrelevant probable causes included in the analysis section
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
The captain (49, ATPL, 16,982 hours total, 5,314 hours on type) and first officer (25, ATPL, 2,247 hours total, 198 hours on type) were preparing the aircraft for departure including reading the checklists requiring the check of the flight crew oxygen system. The first officer conducted these checks and found the oxygen pressure in the normal range at 730 psi. The crew went on with the other preparation procedures, the passengers boarded, the crew was waiting for a delayed last passenger until doors could be closed and the aircraft was ready to depart.
About 30 minutes after the oxygen masks were checked the first officer heard a pop followed by a hissing sound from the right hand side of his seat, fire and smoke came out of the right hand console underneath the #3 cockpit window to the right of the first officer. The captain ordered the first officer to leave the cockpit immediately and notify cabin crew and emergency of the cockpit fire. The captain discharged the fire extinguisher available in the cockpit, however did not manage to put the fire out. The first officer in the meantime notified cabin crew of the cockpit fire prompting an immediate rapid disembarkment via the jetways, then moved on to find somebody with a radio unit, stopped a car on the service way underneath the jetway and radioed the fire department, first fire trucks arrived about 3 minutes after the fire was first observed. Rapid deplanement was completed in about 4-5 minutes. Fire fighters were able to extinguish the fire quickly, all works to extinguish and cool the aircraft were finished about 94 minutes after the onset of fire.
Seven people including passengers, Egyptair personnell and fire fighters suffered from mild asphyxia caused by smoke inhalation and were transferred to hospitals.
The aircraft received substantial damage including extensive fire and smoke damage to the cockpit, two holes were burned through the external aircraft skin at the right hand side of the cockpit, smoke damage occurred throughout the aircraft, heat damage was found on overhead structures aft of the cockpit, isolated areas of heat damage were in the electronic bay below the flight deck where molten metal had dripped down from the flight deck.
The passenger jetway suffered some damage as well including windows were broken due to heat damage, two jacks controlling the canopy at the front were bent due to heat, separation of the canopy, damage to the machine controlling the bridge entrance door due to rushed entry of fire fighters, cracks in the glass of the operator cabin. The jetway was repaired and resumed service on Aug 2nd 2011.
The EAAICD analysed that all actions by the flight crew were prompt and timely, the decision process was efficient and timely. Cabin crew deplaned the passengers efficiently and timely and thus highly contributed to the safety of passengers and crew. Ground crew acted prompt and efficiently after detecting the fire, too.
The aircraft showed no defects that could have contributed to the accident.
The investigation determined there were no fuel, hydraulic or oil lines near the cockpit area where the fire started. The investigation thus focussed on the crew oxygen system reasoning that the speed of the fire development required an accelerant.
The system's stainless steel supply tubes were found without any leakages, the stainless steel spring showed no evidence of arcing/electrical short circuit however most of the wiring was missing near the supply tube with evidence of melting.
The aircraft was found to differ from Boeing's design in that a clamp supporting the first officer's wiring to the oxygen mask light panel was missing. The wiring was not sleeved and a large loop of unsupported wire was found. The investigation determined that about 280 aircraft including all of Egyptair's Boeing 777s were delivered that way.
The flexible oxygen mask hoses were tested for conductivity, some of which were found not conductive with others found conductive.
It was found: "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."
A laboratory analysis concluded: "A short circuit from electrical wiring, which is supposed to be in contact with or routed near the stainless steel oxygen supply tubing, would be the most likely source to provide electrical energy to the spring. It is supposed that the stainless steel spring had been subjected to high energy level, which heated the internal spring until it became an ignition energy source, causing the flexible oxygen hose to ignite and sustain a fire. The time to failure, may took few seconds depending on the amount of energy supplied to the internal spring."
A similiar occurrence, also referenced by the EAAICD, had occurred on a Boeing 767-200 in San Francisco, see Accident: ABX Air Cargo B762 at San Francisco on Jun 28th 2008, on fire while parked, no arson. The EAAICD stated however that the construction of the flight crew flexible oxygen mask hoses of the B762 and B772 differed to an extent that no parallels could be drawn.
This article is published under license from Avherald.com. © of text by Avherald.com.
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