WILMINGTON, OH, USA
N6Y
SWEARINGEN SX-300
THIS SX-300 (SA-29) WAS A PROOF-OF-CONCEPT ACFT BEING DEMONSTRATED FOR THE USAF AT WRIGHT-PATTERSON AFB. THE ACFT WAS CLEARED TO RESTRICTED AREA R5503 AT 8000 FT FOR A DEMONSTRATION. RADIO COMMUNICATIONS WITH INDIANAPOLIS ARTCC WERE ROUTINE; THERE WERE NO DISTRESS TRANSMISSIONS. ABOUT 7 MINUTES AFTER TAKEOFF THE ACFT WAS INVOLVED IN AN INFLIGHT BREAKUP. THE WRECKAGE PATH WAS ABOUT 1 MILE IN LENGTH WITH THE RT WING 3000 FEET FROM THE MAIN WRECKAGE. THE RT WING LOWER ATTACHMENT FITTING EXHIBITED A FATIGUE AREA WHICH PROGRESSED TO FAILURE FROM A WELD NUGGET NEAR THE INTERSECTION OF TWO WELD BEADS. PRE-EXISTING CRACKS WERE ALSO PRESENT IN THE LUG WELD AREA OF THE LEFT WING UPPER AND LOWER ATTACH- MENT FITTINGS. THE ACFT HAD BEEN IN SVC 571 HRS. IT WAS CERTIFIED AS AN EXPERIMENTAL CATEGORY EXHIBITION ACFT. THE DESIGNER HAD STATIC LOAD TESTED THE WINGS TO 6 G'S & SUSPECTED THE ACFT HAD BEEN SUBJECTED TO FLT LOADS APCHG 6 G'S. THE PLT TOLD AN ACQUAINTANCE THAT HE HAD ROUTINELY EXCEEDED THE 'RED LINE' BY 85 MPH.
FATIGUE AND RESULTING FAILURE OF THE RIGHT WING'S LOWER ATTACHMENT FITTING AND INADEQUATE QUALITY CONTROL BY THE SWEARINGEN SX-300 PRODUCTION/DESIGN PERSONNEL.
Source: NTSB Aviation Accident Database
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