Incident Overview
A helicopter experienced a loss of engine power due to mechanical reasons during a maintenance test flight. The pilot performed an autorotation to manage the emergency descent. During the touchdown, the main rotor blades severed the tail boom.
Maintenance History
The maintenance history of the helicopter revealed that the engine had experienced a series of compressor stalls over the last 132 hours of flight. Company management elected to defer required maintenance until after their busy season concluded.
Metallurgical Analysis
Metallurgical analysis of the engine components showed that intergranular corrosion and erosion of the stator vanes had effectively weakened the individual vanes structurally. This condition was identified as part of the investigation into the power loss.
Sequence of Events
The engine experienced a compressor stall during the test flight. The pilot initiated an autorotation, a standard procedure for engine failure. Upon touchdown, the main rotor blades contacted and severed the tail boom.