Accident Sequence
While conducting EMS operations, the helicopter experienced a loss of engine power. The pilot reported hearing a loud bang, followed by the engine spooling down. The pilot performed an autorotation and forced landing, during which the helicopter collided with a chain link fence, resulting in substantial damage.
Postaccident Findings
Postaccident inspection of the engine revealed an uncontained second stage turbine wheel burst (on-speed) as a result of oil starvation and subsequent bearing failure. During the onsite examination, fresh oil residue was noted along the right side of the helicopter's fuselage, tail boom assembly, and leading edges of the tail rotor blades. Oil wetting and staining was also observed on the concrete hangar apron, and a trail of fresh oil extended from the apron to the helipad where the helicopter departed.
Additionally, onsite investigators noted that the oil pressure transducer line coupling B-nut (near the forward bulkhead) was found two flats loose, and four complete rotations from complete separation. Evidence of oil loss, sooting, and localized fire damage was observed in the area of the fitting union.
Maintenance Background
The accident flight was the helicopter's first flight following the completion of a maintenance action item in the general area of the aforementioned fitting. After the maintenance action, an engine run (ground) and post run inspection was completed by a line pilot. No discrepancies were noted, and the helicopter was returned to service. The mechanic who performed the maintenance action was not present during the post run inspection.