A low-pressure turbine rotor blade failed during a test run, causing extensive damage to an aircraft engine. Visual examination showed that the nickel-base superalloy blade broke above the root platform in the airfoil section, leaving a fracture surface with two distinct regions, one characteristic of fatigue, the other, overload. Two dents were also visible on the leading edge, near the origin of the fracture. Based on these observations and the results of SEM fractography, investigators concluded that the blade failed due to fatigue aided by cracks in the surface coating caused by mechanical damage.