What happened
While the aircraft was climbing through 200 feet following takeoff, the right engine separated from the wing. Following this separation, the crew continued the climb and were vectored for a landing. The aircraft landed without further incident and there were no injuries.
The investigation
The investigation focused on the mechanical failure of the engine mounting components. It was determined that the engine separation was caused by the failure of both the aft cone bolt and the engine secondary support assembly.
Detailed examination showed that the two forward cone bolts failed due to overload as the engine swung forward during the separation sequence. The investigation also looked into the specific nature of the initial failures.
Findings
Investigators found that the aft cone bolt failed due to a preexisting fatigue crack. Metallurgical testing revealed that this fatigue was caused by lubricant being inadvertently introduced into the conical surface of the cone bolt. Additionally, the engine secondary support assembly failed because dynamic loads exceeded the designed capacity of the mounting bolts.