What happened
During the takeoff climb phase, the pilot of the Pratt & Whitney Canada PT6A-114A experienced a sudden loss of engine power following an audible heavy impact sound. In an attempt to restore thrust, the pilot moved the power lever through its full range of motion, but the engine failed to respond. The aircraft subsequently entered a forced landing, striking a roadway and nearby vegetation.
Findings
An investigation into the engine revealed that a section of the compressor turbine (CT) vane outer rim had broken off. This liberated metal debris traveled downstream, causing significant damage to the turbine blades and leading to the total loss of engine power. Metallurgical analysis of the fracture surface indicated that the outer rim had failed due to fatigue, with oxidation suggesting the crack had been present for a duration of time.
Records indicated that the engine was operating under an approved extension for its overhaul interval, having reached 4,461.3 hours of the extended 5,100-hour limit. While the operator utilized an engine trend monitoring program in lieu of the standard 1,800-hour hot section overhaul, errors were found in the manual recording of this data. However, investigators determined that even accurate monitoring likely would not have detected the specific fatigue cracking in the vane. Notably, no evidence was found that a borescope inspection had been performed during recent fuel nozzle maintenance, despite manufacturer recommendations to do so to identify such issues.