Aviation incident ENG21LA013

The fatigue fracture and liberation of two airfoils from a low pressure turbine stage 5 nozzle segment that impacted and damaged the downstream low pressure stage 5 blades creating an initial imbalance load in the engine’s low pressure turbine rotor sufficient to allow all the low pressure turbine blades to lose radial blade clearance, contact static structure, and to fracture transversely across the airfoil. The progressive failure of the low pressure rotor caused an increasingly imbalanced load that eventually resulted in the fracture of the oil supply tube that allowed oil to contact hot engine parts and smolder and ignite resulting in the undercowl fire.