McDonnell Douglas MD-369D, Volcano, Hawaii, June 15, 2003 – The commercial pilot and three passengers were killed when the MD-369D lost power and crashed onto a rugged hardened lava flow in the Volcanoes National Park. The NTSB determined that the loss of power, and the accident, was caused by the fatigue fracture and separation of the compressor coupling adapter. The fatigue fracture was attributed to fretting due to both the inadequate design of the coupling and to coaxial misalignment during recent engine maintenance that included removal and replacement of the gearbox. A factor in the accident was the unsuitable nature of the terrain for an emergency landing.
Engine manufacturer Rolls-Royce had records of 12 other compressor-coupling adapters that had fractured and failed, all of which occurred in this specific coupling design. If all elements were in alignment, there would be no significant longitudinal movement of the pilot diameter, the NTSB said. However, any axial misalignment could result in fatigue. One month before the accident, company maintenance personnel had changed out the engine gearbox after finding a loose stud on the gearbox to turbine section mounting.
The MD-369 is registered to K & S Helicopters, Kailua Kona, Hawaii, d.b.a. Tropical Tour Helicopters and was on a 45-minute sightseeing flight over the Pu’u O’o Vents, down toward the shoreline to see molten lava flowing into the ocean, and then back to Hilo International Airport.