Denver International Airport
Aircraft Accident/Incident Report

Denver, Colorado 80249
Wednesday, September 5, 2001 17:14 MDT

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.

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.