MOOSE LAKE, MN, USA
N2841P
PIPER PA-20
THE ACFT (PIPER PA-22, CONVERTED TO A PA-20, IAW STC SA45AM) WAS BEING USED TO PROVIDE A BIENNIAL FLT REVIEW FOR THE OWNER/PLT (CONSIDERED AS PIC ON THIS FLT). DRG FLT, THE RGT WING FOLDED BACK OVER THE FUSELAGE & THE ACFT CRASHED. AN EXAM OF THE WRECKAGE REVEALED THE FWD LIFT STRUT FOR THE RGT WING HAD FAILED IN AN AREA OF SEVERE CORROSION. THE FAILUREOCCURRED AT THE LOWER PART OF THE LIFT STRUT NEAR THE FUSELAGE ATTACHMENT POINT. AN EXAM OF THE ANNUAL INSPN CHECKLIST INDCD ALL APPLICABLE AIRWORTHINESS DIRECTIVES (AD'S) WERE COMPLIED WITH AS OF 7/21/89 & THAT THE LIFT STRUTS WERE VISUALLY INSPD AT THE ANNUAL INSPN. THE ACFT LOGBOOK SHOWED THAT AD 77-03-08 (REQUIRING MECHANICAL TESTING OF THE LIFT STRUT FOR EVIDENCE OF CORROSION AT 5 YR INTERVALS) HAD BEEN COMPLIED WITH IN JULY 1988. THE AROMA OF LINSEED OIL WAS NOTED IN ALL LIFT STRUTS, BUT POLYMERIZED LINSEED OIL WAS FOUND IN THE RGT & LEFT REAR STRUTS. INTERNAL CORROSION HAD PERFORATED THE RGT FWD LIFT STRUT PRIOR TO ITS FAILURE.
SEVERE CORROSION OF THE LOWER FORWARD LIFT STRUT FOR THE RIGHT WING, INADEQUATE INSPECTION OF THE LIFT STRUT BY MAINTENANCE PERSONNEL, AND SUBSEQUENT FAILURE OF THE LIFT STRUT, WHICH RESULTED IN AN OVERLOAD FAILURE (FOLDING BACK) OF THE WING. RELATED FACTORS WERE: INADEQUATE INSPECTION PROCEDURES PROVIDED BY THE MANUFACTURER & INADEQUATE SURVEILLANCE BY THE FAA.
Source: NTSB Aviation Accident Database
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