Denver, CO, USA
G-VIIK
Boeing 777-236
During refueling, with the airplane parked at the gate to unload passengers, a pressurized refueling hose broke loose from the airplane and a fire erupted. The hose which broke loose was the inboard of two hoses which had been attached by the refueler to the left wing refueling panel. Examination of the hose revealed that it came loose due to the fracture of the three refueling adapter ring locking lugs on the airplane's inboard left wing refueling port. Metallurgical examination of the inboard (fractured) adapter and the outboard adapter indicated that although the inboard adapter had a different microstructure and probably a different heat treatment history from the outboard adapter, they both met the applicable requirements for ultimate tensile strength and chemistry. Additionally, the metallurgical examination found the locking lug fractures to be the result of a one-time ductile overstress with no indications of preexisting cracking, corrosion, or defects that would have degraded the load-carrying capacity of the adapter. Therefore, the failure of the adapter was the result of an overload applied at the time of the separation. The investigation revealed that the refueler had improperly positioned the hydrant truck in relation to the airplane's left wing refueling panel prior to commencing refueling operations. Because of this positioning, the lift platform's left railing obstructed the normal nozzle attachment procedure to the airplane's inboard manifold adapter. Subsequently, while attaching the nozzle, the refueler improperly routed the hose over the top of the front railing, around the left forward corner support of the railing structure, and aft to the airplane's inboard manifold adapter ring. The investigation also revealed evidence consistent with the refueler lowering the lift platform, for personal comfort during the long refueling, and the refueling hose then catching on the platform's left front railing and bumper. Vertical pull tests indicated that the three nozzle attachment lugs were capable of supporting a load in excess of 10,000 pounds if the load was applied along the nozzle centerline. However, the weight bearing capability of the lugs dropped off as the load was applied at increasing angles off the centerline. At an angle of 30 degrees off centerline, the lugs failed below 1,000 pounds of load. The refueler's improper routing of the fuel hose would have placed an off-axis load of approximately 52 degrees. The angular force applied to the manifold adapter ring was amplified when the refueling hose was pressurized. The combination of the two forces resulted in the adapter ring's failure. Pressurized fuel discharged forming a fuel mist cloud that subsequently ignited. The resulting fire resulted in fatal injuries to the refueler. The airplane's lower leading edge panels, the refueling control panel, and the outboard portions of the left engine fan cowl and thrust reverser were thermally damaged. The hydrant truck was destroyed in the fire. Since the accident, two companies have introduced modifications to help position hydrant dispenser trucks during single person operations, and industry groups are examining the need for changes to existing industry standards and practices of aircraft fueling.
HISTORY OF FLIGHT On September 5, 2001, at 1714 mountain daylight time, a Boeing 777-236, British registration G-VIIK, was substantially damaged during a ground fire at Denver International Airport, Denver, Colorado. The fire started when the airplane was parked at the gate unloading passengers and being refueled. The captain, first officer, a third pilot, 13 cabin crewmembers, and 10 passengers who were on board at the time of the accident, were not injured; however, the ground service refueler was fatally injured. British Airways was operating the airplane, Flight 2019 (call sign BAW91F), under Title 14 CFR Part 129. Visual meteorological conditions prevailed for the 9 hour 38 minute cross-country flight that originated from London, United Kingdom. The airplane departed Gatwick International Airport, London, United Kingdom, at 0713 with 256 passengers, and was cleared to land on runway 16 at Denver International Airport (DEN) Denver, Colorado, at 1646 (the scheduled arrival time was 1615). Federal Aviation Administration (FAA) Air Traffic Control (Denver tower) instructed BAW91F to contact Denver ramp control, for taxi instructions, at 1656. BAW91F was cleared to taxi to gate A37, and its flight data recorder indicates that its auxiliary power unit (APU) was started at 1658 and its engines were shut down at 1706. A British Airways Senior Air Safety Investigator stated that the airline's Boeing 777's APU is normally started during taxi-in, and the airplane's electrical load is transferred from the main engines to the APU automatically via "no-break" technology when the engines are in idle, or during shut down. The captain for the flight said that during short time turn around, ground power is not used. He said that at the time of the accident, the airplane's electrical power supply was being generated by its APU. The refueling hydrant truck was parked under the airplane's left wing, facing aft, and outboard of the left engine. Videos taken from DEN firefighting equipment showed that the hydrant truck had been chocked, and the hydrant truck's hydrant coupler had been attached to the airport's subsurface pit hydrant. The DEN fire department's video and a United Airline's maintenance-engineer also confirmed that the refueler had grounded the truck to the pit hydrant, and bonded the truck to the airplane's left main landing gear. The maintenance-engineer said the refueler had raised the lift platform and had attached two hoses to the airplane's left wing refueling manifold system. As the maintenance-engineer approached the hydrant truck, he noted that refueling of the airplane had already started. He further stated that he frequently saw refuelers lower their lift platforms for head clearance comfort (during the refueling), and/or to receive their refueling requirements from a maintenance-engineer. He did not remember seeing the lift platform move on this occasion. The maintenance-engineer said he positioned himself between the airplane's left engine and the hydrant truck to tell the refueler what fuel load should be put on the airplane. He said the refueler turned towards him and leaned down, with his back to the refueling hoses, to give him the amount of fuel that remained from the previous flight. He said the refueler had the dead-man fuel control (shut off device) in his left hand, and the hydrant truck's fuel flow meter was beginning to rotate rapidly. The last reading he remembered seeing on the fuel flow meter was 60 gallons. He further noted that the hydrant truck's turbo-diesel engine was running. As the maintenance-engineer looked up at the refueler, he observed the inboard fuel hose separate sideways (forward, in relationship to the truck) from the airplane, and flap around "violently spraying fuel in all directions." He yelled at the refueler that the "hose was loose." The maintenance-engineer was immediately soaked with fuel and even swallowed some. He said the flames propagated up from the bottom of the truck, through the open lattice of the lift platform floor, and "engulfed the fueler." He immediately ran for a large fire-extinguishing bottle. A second maintenance-engineer was standing inboard of the left engine when he "felt the heat and turned and looked to see a huge fire had broken out at the fuel truck [hydrant truck]." The airplane's captain was standing inside the airplane near the door to the jetway. He said that a flight attendant was the first crewmember to notice the fire; her alarm motivated him to move to a jetway window to view aft. He said that he observed a "fire near [the] left engine," and he ordered all remaining persons to immediately evacuate the airplane. A pilot standing nearby said that a large ball of fire enveloped the hydrant truck and much of the airplane's left wing; he said the heat was very intense. He yelled to another person to call the fire department. He ran to assist a maintenance-engineer in retrieving a large fire extinguisher bottle. The fire department received the call at 1714, arrived at the scene at 1717, and immediately extinguished the fire. Several civilian witnesses, inside the concourse, made the following observations: the first witness observed "men refueling [the airplane]. I saw the hose fly up and a spray covered the vehicle (looked like a jet of water). I then saw a small fire followed by a large ball of fire engulf the vehicle. Various people were running away from the vehicle as the fire continued to grow." She said she then thought there was some "smoke" or vapor before the fire started. She recalled the fire starting from the truck, but could not be specific whether it was from the basket or the body of the vehicle. A second witness "noticed that there was a spray of clear fluid coming from around where the people were refueling the jet. I thought it could be water, but noticed a number of the people running away and then thought it must be fuel. Shortly afterwards (1 second?) I saw the fuel explode and engulf the truck and engine of the plane." During a second interview in England, this witness recalled, "seeing the fire first in the basket, then down onto the truck. The fireball then enveloped the fuel truck, then the refueler, then up below the wing to the engine with an orange flame." A third witness said, "I was watching the servicing of British Airlines Flight 2019, when suddenly [I] saw a huge fountain of liquid (presume jet fuel) in the air followed by a huge ball of flame. As they were refueling the aircraft, I would think either the hose ruptured or the coupling failed." A fourth witness said, "I saw a flash, followed by an expanding fireball. After taking cover, it appeared the refueling stand behind [the] port wing was on fire." A fifth witness said, "[the] fire started ground." Additional witnesses said, "I saw that [the] engine explode, fire was coming from the engine." Another said, "explosion either from the engine or right in front of the engine. The fire was surrounding the engine and wing. The fire was also spreading on the ground." Another said, "I saw what appeared to be smoke coming from the engine whilst the re-fueling truck was re-fueling. There was a sudden flash and the truck [and the] engine was engulfed in flames." Another said, the fire started from the top of the wing and came down. Another said, "I looked up to see flames that looked like they were coming from the engine on the right side. Then it looked like a truck or something behind the engine was also on fire." And one more said, "The left outboard engine was suddenly engulfed in flames. Could see a fuel truck behind this engine. Flame appeared to spread over more of the A.C in the vicinity of the left outboard engine. Fuel was burning on the ground." According to a British Airways representative, the 26 individuals still on-board the airplane at the time of the accident were evacuated through the jetway without incident. PERSONNEL INFORMATION Aircraft Service International Group (ASIG) hired the refueler on October 14, 1997. ASIG records indicate that he had received training and was qualified to refuel 17 different aircraft for 10 different airlines (he was qualified on the Boeing 777 on April 27, 1999; it was not determined how many Boeing 777s he had actually fueled). He had refueled one previous airplane (a Lufthansa A340-313X), on the afternoon of the accident, using hydrant truck number 9417. He completed that refueling approximately 30 minutes before the accident. At the time of the accident, the refueler was wearing a cotton shirt, and pants made of 65 percent polyester and 35 percent cotton. The first maintenance-engineer (with 24 years of aviation maintenance experience) said, in a Denver Police Department interview, regarding the ASIG fueler, "He is generally not the one assigned to that plane, I believe." The second maintenance-engineer (with approximately 30 years of aviation maintenance experience) said regarding the fueler, "He wasn't one of the normal guys; I haven't seen him very often." According to the Denver Police Department, the refueler was 5 feet 11 inches tall, and weighed 160 pounds. The refueler died from his injuries on September 11, 2001. He was 24 years old. AIRCRAFT/VEHICLE INFORMATION General Information about the Airplane The airplane, a Boeing 777-236, was a twin engine, turbofan aircraft with a maximum gross takeoff weight of 590,000 pounds, and was manufactured in 1998. At the time of the accident, there were 359 similar aircraft in use worldwide, of which British Airways operated 44. The airplane's flight deck seats four, and an additional 14 cabin crew positions were located in the cabin area along with seats for a maximum of 267 passengers. Two General Electric Model GE-90 engines powered the airplane with a maximum takeoff thrust at Denver, Colorado, of 90,000 pounds each. The GE-90 engines were suspended by pylons from each wing, and their outer cowling dimension was 13.3 feet in diameter at their greatest point. A representative from British Airways said that at the time of the accident, the airplane had completed approximately 2,100 cycles, and had approximately 14,000 flight hours. He said that the airplane's records suggest that the airplane had been refueled approximately 2,000 times. Airplane's Fuel System The airplane was equipped with three fuel tanks, with a maximum capacity of 45,200 gallons of fuel. There were two fueling stations, one on the leading edge of each wing. Both stations contained two refueling adapters, but there was only one refueling control panel and it was located at the left wing refueling station. The under-wing refueling panel was located approximately 43 feet outboard of the centerline of the aircraft, or 64 inches outboard horizontally from the engine. The refueling panel on the Boeing 777 was originally designed to be approximately 50 feet outboard of the centerline (approximately 19 feet from the ground), to place it further from the engine. Because the Boeing 777's wing is one of the highest from the ground in the industry, the original location for the refueling panel would have required refueling-hydrant trucks to be supplementally stabilized with outriggers to meet American National Standards Institute, ANSI/SIA A92.7 (Airline Ground Support Vehicle-Mounted Lift Devices) requirements. To avoid the need for outriggers on refueling-hydrant trucks, the refueling panel was moved 13 feet inboard, to its present location, which is approximately 17 feet 6 inches from the ground. The airplane's fueling manifold system provide four single-point connections (two on each wing), each equipped with a three-lug adapter ring for attaching the refueling nozzle. The adapter ring geometry is an industry standard specified in MS24484. The adapter rings on the B-777 are made from a copper, nickel, and aluminum alloy (C95500; aluminum-bronze), heat treated for strength enhancement. The adapter rings had a machined shear groove, which was designed to fail in case a refueler drives away with the nozzles still attached to the airplane. The adapter's design was meant to prevent leaks by protecting the airplane's fuel system during a mechanical overload. At the time of the accident, the airplane was equipped with its original refueling adapter rings. Ground Fuel Supply and Dispensing Fuel (aviation Jet A) from Denver International Airport's fuel farm currently flows south towards the three east-west passenger concourses in four 20-inch in diameter pipes at 185 psi (pounds per square inch). Two pipes are on the east side of the concourses, and two are on the west side. One pipe from each pair services the north side of the concourses and the other the south side. Only the east side was in operation on the day of the accident. The distribution pipes that travel parallel to the concourses are 16-inch pipes and narrow down to 14-inch pipes, and have a static pressure of 150 psi. Each airplane-parking gate has a subsurface pit hydrant, which is fed by a 6-inch pipe at 120 psi. During refueling operations, pit hydrant pressure may vary from 80 to 120 psi. Current fuel demands at Denver International Airport require only 4 of their 16 fuel pumps (located at the fuel farm) to move an estimated 1 million gallons of fuel per day. The fuel distribution system is designed to provide uniform pressures at all of the gate pit hydrants and to dissipate fuel pressure surges, which are created by multiple starts and stops of refueling operations. The hydrant dispenser, mounted on a 1999 Ford F550 chassis (ASIG #9417; total miles on the odometer, 1,024), provided final filtering, metering, and pressure control for fuel entering an airplane. The truck was powered by a 7.3L turbocharged diesel engine. The hydrant dispenser was constructed to reach the Boeing 777 refueling station, which at 17 feet 6 inches is the highest in the commercial aviation fleet. The chassis and cab met standard automotive design criteria. The muffler was located under the passenger's seat, and its tail pipe was directed towards the right side of the cab. The hydrant dispenser, mounted on the truck's rear chassis, met all National Fire Protection Association (NFPA) standards. The lift platform was located directly behind the cab. The hydrant dispenser's components, including the hydraulically actuated lift platform, filter, valves, meter, and hoses were constructed and assembled at Tampa, Florida during April and May 2001. The completed vehicle was shipped to Denver, Colorado, on May 9, 2001, and went into service on May 22, 2001. The vehicle was inspected daily, and a more extensive inspection was accomplished every 30 days in accordance with the requirements of the Air Transport Association 103 standard. The last 30-day inspection occurred on August 24, 2001. The hydrant dispenser was equipped with two vertical cylinder pressure surge protectors, which led to a 250-gallon filter vessel. The dispenser had a maximum rated flow capability of 755 gallons per minute (gpm). The last non-restricted flow test of the hydrant dispenser was on August 24, 2001, and had a maximum flow of 540 gpm, with a nozzle pressure of 38 psi. Down stream from the filter was a Jac-Riser hose assembly, which provided the flexibility needed for the 4 foot by 7 foot lift platform to move up and down. The lift platform had two swivel fuel manifolds that delivered pressurized fuel to two 10-foot long Goodyear Wingcraft 2 1/2-inch (inner diameter) aircraft fueling hoses (type c, grade 2). According to representatives of the BF Goodrich Company, the hoses met or exceeded the requirements of American Petroleum Institute no. 1529 and National Fire Protection Association no. 407 specifications. The hydrant dispenser, including all hoses, valves, and filter vessel, had an estimated static fuel capacity of 400 gallons. The two hoses were equipped with nozzles and ferrules in March 2001. These hoses had a strength test rating of 20,000 pounds and were strength test rated (ferrule to ferrule) at approximately 1,600 to 1,800 pounds. Their outer covers were electrically semi-conductive. The assembled hoses were hy
the overstress fracture of the airplane's refueling adapter ring that resulted from the abnormal angular force applied to it. The applied angular force occurred due to the ground refueler inadequately positioning the hydrant fuel truck (in relation to the airplane), and his inattentiveness while lowering the refueling lift platform, thus permitting the refueling hose to become snagged and pulled at an angle. The fracture of the adapter ring during the refueling led to the ignition of the pressurized (mist producing) spilled fuel and subsequent fire.
Source: NTSB Aviation Accident Database
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