Event Description
A Pilatus PC-12/45 departed into instrument meteorological conditions. As the airplane entered clouds, loud bangs were heard from the engine and flame was observed coming from the left side engine exhaust. The pilot in command pushed the nose over and aimed the airplane toward where he thought the airport was, while the second pilot initiated engine shutdown. The airplane touched down long and fast on a wet runway. The pilot intentionally yawed the airplane, causing it to depart the runway in a nose-right 60-degree skid, and struck a chain link fence about 300 feet beyond the departure end of the runway.
Engine Examination
Examination of the engine revealed that the #1 bearing had failed. Electrical pitting was found on the gears in the accessory drive between the starter-generator (SG) attach point and the #1 bearing. Approximately 704 hours earlier, the SG had an unscheduled replacement. Records indicated that the SG had burn marks on the stator vanes and armature; however, the initiating event for the SG failure was not determined.
Historical Context
Other engines were identified as having experienced electrical discharge damage (EDD), all of which preceded the accident. Each event occurred on a multi-engine airplane and resulted in an in-flight shutdown, followed by a single-engine landing. None of the starter generators that were identified as the source of the EDD were original equipment manufacturer (OEM), and all had been previously overhauled. Additional engines were identified as having experienced EDD; however, the records on the engines were incomplete, and there was no starter generator history to review. Goodrich published an overhaul manual for the starter-generator. In the manual they stated that only Goodrich replacement parts should be used, and the use of non-Goodrich parts would void their warranty. However, there was no FAA requirement that the overhaul be conducted by an FAA approved repair station, or that only Goodrich parts be used as replacement items.