Michiana Regional Airport
Aircraft Accident/Incident Report

South Bend, Indiana 46601
Friday, August 27, 1999 11:10 CDT

The airplane sustained an in-flight failure of the right engine. The captain performed the checklist to shut down the engine and performed the single engine landing. No injuries were reported. A review of the engine history revealed that this was the third "in-flight shutdown" for this engine. The engine's time since new was 21,101.8 hours, its time since overhaul was 2,414.3 hour, and its time installed on the airplane since its last maintenance was 76.4 hours. The reason for the last maintenance was an "in-flight shutdown." The accessory section was examined at the NTSB Materials Laboratory. The report stated that the spur gear appeared undamaged. The spur gearshaft had portions of teeth missing. The housing had markings and impressions consistent with splined spur gear contact. The splined spur gear was found fractured and deformed into an oval shape, resulting in a gap between the mating fracture faces. The outer surfaces parallel to the circumferential plane of the splined spur gear appeared rubbed, and portions had a blue-purple tint consistent with frictional heating. Areas of the fracture surfaces also had a similar blue-purple tint. Portions of five external gear teeth were missing. All of the internal spline's teeth peaks were missing and the teeth were deformed. One radial fracture face had smooth flat features, consistent with fatigue and crack arrest lines were found. The fatigue had multiple origins. Inner diameter origins were located in the root of a spline. The contact surface of the spline tooth adjacent to the fracture origin was deformed consistent with rotational contact with spline crowns. Hardness of the splined spur gear was measured to be 38 HRC, which was within its specified range.

the right engine accessory section's splined gear spur gear failure during cruise flight.