A Boeing 767-281 Freighter Aircraft had been loaded for a cargo flight from San Francisco International Airport (California, USA) to Wilmington-Clinton Field (Ohio, USA), on board a crew of two and a load of cargo.
The fire damaged aircraft (© NTSB)
Earlier during the day maintenance personnel had performed a service check of the aircraft. No abnormalities were found during this check.
As the flight crew was completing their preflight checks, they tested their individual oxygen masks and checked the oxygen system pressure on the EICAS (Engine Indicating and Crew Alerting System). While the crew was completing the engine start checklist they heard a "pop" followed by hissing sounds. A short while later the co-pilot remarked that there was something going on in the back. followed by an exclamation "We got a fire .....got a big fire", while the lavatory smoke detector and a fire warning bell activated. About a minute prior the co-pilot had checked the supernumerary compartment and switched off the area lights, at that time there was no smoke or fire in the area. When looking back the copilot saw smoke and fire in the area where the oxygen system was located for the supernumerary compartment. The captain could smell the smoke but did not see the fire.
The fire damage to the supernumerary compartment (source: baaa-acro.com © unknown)
At 22.11:04 the co-pilot contacted ATC informing them of the fire and the need to get the ARFF (Aircraft Rescue and Fire Fighting) on site. ATC replied that the trucks would be rolling. The pilots initiated the fire and evacuation checklist, this caused the CVR to stop recording at 22.11:38.
Because of the location of the fire, the crew could not use the Entry door and the Service door, located in the supernumerary compartment, The co-pilot escaped from his side window using the escape rope, once on the ground, he instructed ground staff to place stairs under the captain's side window, who opened his window and escaped via the stairs.
At that time black smoke was pouring out of the aircraft.
The aircraft with external fuselage reinforcements
(Souce baaa-acro.com © Ian Abbott)
The National Transportation Safety Board investigated the fire and published its report on the 30th of June 2009. In their report, they provided an overview of maintenance reports related to servicing the oxygen system on the incident aircraft. In the period between January 2007 and June 2008, the oxygen system was serviced 50 times and over that same period, 4 oxygen leaks were recorded in the aircraft's technical records, (The full report is available by clicking here). They determined that the probable cause of the fire was;
"The design of the supplemental oxygen system hoses and the lack of positive separation between electrical wiring and electrically conductive oxygen system components. The lack of positive separation allowed a short circuit to breach a combustible oxygen hose, release oxygen, and initiate a fire in the supernumerary compartment that rapidly spread to other areas. Contributing to this accident was the Federal Aviation Administration’s failure to require the installation of nonconductive oxygen hoses after the safety issue concerning conductive hoses was initially identified by Boeing."
Eleven safety recommendations were made to the FAA and one to the operator as a result of the investigation.