Williams Gateway Airport
Aircraft Accident/Incident Report

Mesa, Arizona 85212
Wednesday, November 17, 1999 16:49 MST

Following a loss of engine power on the ex-British military jet fighter just after liftoff, the pilot aborted the takeoff on the runway but could not stop prior to over-running the departure end and colliding with a fence and a berm. The pilot and crew chief said that about 5-10 seconds after takeoff a significant compressor stall happened with a loud explosion, followed by engine spool down. The airplane is a two-seat ex-military jet fighter produced in the 1950's and early 1960's by Hawker for service in the British Royal Air Force. Following the airplane's surplus from the RAF, it was imported into the United States and was being flown under a FAA special airworthiness certificate in the experimental category for the purpose of exhibition and racing. According to records at Rolls-Royce, the engine was manufactured in 1954 and sent to the RAF as part of a spares contract. The engine was last in the factory overhaul facility on March 26, 1981, for overhaul at 251 hours TSO. The engine is life limited to 450 hours between overhauls. The last manufacturer's records on this engine documented its installation in another Hawker Hunter by the RAF in 1983, with 392 hours TSO. The operator's engine maintenance records began on June 27, 1990, and documented its installation in the accident airframe at a maintenance facility in Wisconsin. An unsigned handwritten note preceded this entry and stated that the engine had a total run time since overhaul of 436 hours, with 265 hours remaining to overhaul. No documentation was available to support the engine history between leaving RAF service and the installation in the accident airframe. The last entry in the records was dated July 2, 1999, and consisted of an annual inspection at a time of 548 hours since last overhaul. A partial engine disassembly revealed that three third stage compressor blades had fractured from their root fixing lugs and separated. All compressor blades from stages 5 through 10 had fractured through their airfoil sections just outboard of the root. The root lugs from the failed third stage were removed and submitted for metallurgical analysis. All three blades failed due to high cycle fatigue failures, which initiated in the bores of the lug fixing pins. Energy Dispersive X-ray revealed corrosion cracks and pits at the crack initiation site. This engine has a history of high cycle fatigue failures of stage 3 compressor blades due to corrosion pits. Two modifications were introduced by the manufacturer, which incorporated a strengthened lug and a silicon rubber sealant to the bore interface to prevent the corrosion induced fatigue failures. The modifications were performed by the RAF between 1983 and 1986 to in-service and spares stock engines. This engine did not have these modifications incorporated.

The fatigue failure and separation the stage 3 compressor blades due to corrosion pitting of the blade retention lug bores. A factor in the accident was the failure of the various post military surplus operators of this engine to incorporate the manufacturer's recommended modifications to prevent such failures.