On December 30, 1998, an Ercoupe (eng & Research Corp.) 415-C (registration N99371) was involved in an aviation accident near San Ysabel, CA. Investigators recorded the probable cause as: Fatigue failure of the crankshaft forward of the oil-slinger flange, with the fatigue origin in an area mechanically damaged during the fracture. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise at 4,500 feet, an engine vibration intensified, leading to a crankshaft fracture and propeller separation. The pilot executed a forced landing on uneven terrain, collapsing the nose gear. Investigation revealed fatigue failure of the crankshaft originating from mechanically damaged area.
Accident Sequence
The aircraft was in cruise flight at 4,500 feet when the pilot added power as the terrain began to rise. Shortly after, the engine started to vibrate. The pilot looked down to check the mixture and carburetor heat, and the vibration intensified. The crankshaft then fractured, and the propeller separated from the airplane. The pilot subsequently performed a forced landing on uneven terrain. During the landing, the nose gear collapsed.
Investigation Findings
A metallurgical laboratory examination of the remaining crankshaft piece determined that the crankshaft separated forward of the oil-slinger flange due to fatigue. The fatigue region had an origin point in an area that had been mechanically damaged during the crankshaft failure.
Probable cause
Fatigue failure of the crankshaft forward of the oil-slinger flange, with the fatigue origin in an area mechanically damaged during the fracture.
What happened in the 30 Dec 1998 Ercoupe (eng & Research Corp.) 415-C accident near San Ysabel, CA?
During cruise at 4,500 feet, an engine vibration intensified, leading to a crankshaft fracture and propeller separation. The pilot executed a forced landing on uneven terrain, collapsing the nose gear. Investigation revealed fatigue failure of the crankshaft originating from mechanically damaged area.
What aircraft was involved and where did it happen?
The accident on 30 Dec 1998 involved an Ercoupe (eng & Research Corp.) 415-C, registration N99371, at San Ysabel, CA.
What was the probable cause of the accident?
Fatigue failure of the crankshaft forward of the oil-slinger flange, with the fatigue origin in an area mechanically damaged during the fracture.
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