On August 30, 1986, an Ercoupe (eng & Research Corp.) 415C (registration N3002H) was involved in an aviation accident near Prosser, WA. Investigators recorded the probable cause as: Progressive crack in rib #7 emanating from previous damage to the leading edge of the left wing tip, resulting in inflight structural overload of the main spar. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A left wing suffered an in-flight structural failure while the pilot was practicing fly-bys for an upcoming airshow. Investigation found a progressive crack in rib #7 caused by previous leading edge damage.
What happened
The pilot was conducting practice maneuvers for an airshow scheduled for the following day. During these operations, the aircraft experienced an in-flight structural failure of the left wing.
The investigation
Examination of the wreckage revealed a progressive crack originating in rib number seven. This crack emanated from previous damage sustained to the leading edge of the left wing tip. The structural integrity of the main spar was subsequently compromised by this overload.
Findings
The primary contributing factor was progressive fatigue cracking in the wing structure. Pre-existing damage to the wing tip leading edge initiated the failure sequence, which ultimately led to inflight structural overload of the main spar.
Probable cause
Progressive crack in rib #7 emanating from previous damage to the leading edge of the left wing tip, resulting in inflight structural overload of the main spar.