On July 18, 1992, a Piper PA-25-260 (registration N4766Y) operated by Air Aid, Inc. was involved in an aviation accident near Decker, IN. Investigators recorded the probable cause as: Metallurgical examination revealed preexisting fatigue cracks in the lower spar cap of the right wing originating from two misdrilled holes, and an airworthiness directive to inspect for wing spar fatigue cracks had not been complied with. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application maneuver, the right wing separated from the airplane, leading to a crash and post-crash fire. Metallurgical examination found preexisting fatigue cracks from misdrilled holes; an airworthiness directive had not been complied with.
Accident Overview
The accident occurred during an aerial application maneuver. The pilot initiated a pull-up to execute a reversal turn. During this maneuver, the right wing separated from the airplane. The aircraft subsequently crashed in a field and was consumed by a post-crash fire.
Metallurgical Findings
A metallurgical examination of the right wing structure revealed preexisting fatigue cracks in the lower spar cap. These cracks originated from two misdrilled holes in the spar cap. The fatigue cracking was present prior to the accident and contributed to the structural failure that led to the wing separation.
Compliance Issue
An airworthiness directive (AD) had been issued requiring inspection for wing spar fatigue cracks. The investigation determined that this AD had not been complied with. Non-compliance meant that the existing fatigue cracks were not detected and corrected before the accident flight.
Probable cause
Metallurgical examination revealed preexisting fatigue cracks in the lower spar cap of the right wing originating from two misdrilled holes, and an airworthiness directive to inspect for wing spar fatigue cracks had not been complied with.