Ercoupe 415-D N99154 accident near Sebring, Florida

Probable cause

The pilot's exceedance of the design stress limitations of the airplane.

NTSB analysis

Witnesses observed the accident airplane as it performed a low-level, local flight in the vicinity of the passenger's home. The witnesses reported that the airplane entered a high-speed dive before pulling up and rolling steeply left. One of the witnesses reported that both ailerons were "fluttering" just before both wings separated from the fuselage and the airplane broke up. Examination of the wreckage revealed that the wing spar failed in overload at its center, in an aft and downward direction. Though a hole not specified in the design of the airplane was present at the point where the separation of the spar began, its effect on the preaccident structural strength of the spar could not be determined. No corrosion or evidence of a fatigue failure was observed in the vicinity of the initial separation.

Text from the NTSB. Open the NTSB docket for ERA09FA087 for the full record.