NTSB Identification: ATL89MA070.
The docket is stored on NTSB microfiche number 38326.
Accident occurred Monday, January 09, 1989 in WILMINGTON, OH
Probable Cause Approval Date: 06/01/1989
Aircraft: SWEARINGEN SX-300, registration: N6Y
Injuries: 2 Fatal.

NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft accident report.

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.

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

FATIGUE AND RESULTING FAILURE OF THE RIGHT WING'S LOWER ATTACHMENT FITTING AND INADEQUATE QUALITY CONTROL BY THE SWEARINGEN SX-300 PRODUCTION/DESIGN PERSONNEL.

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