Incident Details
A helicopter pilot reported that while on approach to land at approximately 100 to 150 feet above ground level, the engine lost power as though it had flamed out. The pilot entered an autorotation but was unable to reach the helipad. Subsequently, the helicopter landed in trees and was badly damaged.
Investigation
During the investigation, the engine was removed from the airframe and operationally checked, but no reason was found for the power loss. Disassembly of the engine revealed several discrepancies; however, none of these would have singularly resulted in a flame-out.
Engine Examination
An examination of the engine's internal combustion liner revealed an overtemperature blister, cracks on the flange, and non-approved welds. Additionally, a required modification of the liner had not been completed. The igniter and fuel nozzle mounting pad on the outer combustion liner was slightly displaced (0.009 inch from perpendicular), resulting in a slight displacement of the flame pattern inside the inner liner. The #1 power turbine nozzle was burned, cracked, and eroded. There was evidence that the engine had experienced one or more overtemperature conditions, possibly from hot starts, high power levels, or lack of cooling before engine shutdowns.