NTSB Identification: FTW97FA220.
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Accident occurred Saturday, June 14, 1997 in CORNING, AR
Probable Cause Approval Date: 05/04/1998
Aircraft: AYRES S2R-T34, registration: N3103D
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The left wing of an agricultural airplane separated in flight while maneuvering during an aerial application flight. A witness observed the left wing of the airplane falling to the ground and the 'airplane cork screwing to the ground.' The left wing came to rest 90 yards from the tree line, with the main wreckage coming to rest approximately 289 yards beyond the left wing. A metallurgical examination of the fractured wing revealed that the separation of the lower spar cap was the result of a fatigue crack that emanated from the 1/4 inch diameter hole for the center splice fitting. The examination also revealed that the tensile strengths for the left wing spar cap was lower that that specified in the engineering drawing provided by the manufacturer. A review of the airframe records revealed that Ayres Service Bulletin No. SB-AG-39 ('Wing Spar Inspection and Fatigue Life Extension'), issued 17 September 1996, had not been complied with by the operator. This SB included procedures for accomplishing a magnetic particle inspection around the lower spar cap's bolt holes.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The in-flight separation of the left wing as result of fatigue crack of the lower spar cap due to inadequate materials by the manufacturer. A factor was the operator's failure to comply with a published service bulletin on the airframe.

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