On April 1, 1996, a Cessna 500 (registration N727TK) was involved in an aviation accident near Salt Lake City, UT. Investigators recorded the probable cause as: A fatigue crack that originated from the aft face in the area containing a circumferential groove mark produced during machining of the aft face prior to blue etch anodizing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During takeoff, a loud boom preceded right engine power loss. Pilot aborted and taxied back. Inspection revealed an uncontained failure; impeller fracture originated from a machining groove mark.
Incident Overview
A pilot reported that during the takeoff ground roll, a loud 'boom' was heard, and the right engine lost power. The pilot aborted the takeoff and immediately brought the thrust lever to idle power. As the airplane turned off the runway onto a taxiway, the right engine 'blew.' The pilot continued taxiing back to the fixed base operator.
Post-Event Inspection
After the airplane was secured, the pilot inspected the right engine and found evidence of an uncontained engine failure. Debris from the right engine had punctured the side of the pressure vessel and damaged the wing. Further inspection revealed the engine impeller had broken into two large pieces.
Metallurgical Examination
A metallurgical examination of the impeller determined that a fatigue crack had originated from the aft face in the area containing a circumferential groove mark that was produced during machining of the aft face prior to blue etch anodizing. This crack led to the fracture of the impeller and the subsequent uncontained failure.
Probable cause
A fatigue crack that originated from the aft face in the area containing a circumferential groove mark produced during machining of the aft face prior to blue etch anodizing.