NTSB Identification: ATL05FA079.
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Accident occurred Monday, May 09, 2005 in Kissimmee, FL
Probable Cause Approval Date: 05/30/2006
Aircraft: North American SNJ-6, registration: N453WA
Injuries: 2 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 purpose of the flight was to familiarize the student pilot with the airplane within a 30-minute flight lesson, when the certified flight instructor demonstrated various flight and aerobatic maneuvers. Witnesses further observed the airplane enter a spin, and descended rapidly and collided with the ground. Post accident examination of the accident site revealed that the engine, propellers, main fuselage, left wing assembly, vertical and horizontal stabilizers were located in a crater 10-feet in diameter and 6-feet in depth. The right wing assembly was located 0.13 nautical miles on a 354-degree heading from the main wreckage site. No radio transmissions were received from the pilot prior to the accident. Post examination of the right wing revealed it separated due to the fatigue failure of the forward lower attach flange at the inboard side of the right wing attach joint. The fatigue fracture had a primary origin area at the lower surface of the horizontal leg of the flange at the outboard edge of the spot face for the fastener in the outboard fastener row located closest to the forward end of the flange. The fatigue crack propagated relatively slowly upward until it extended nearly through the thickness of the flange and was 2.3 inches long at the lower surface. Additionally slow-growth fatigue cracks were present at the outboard edges of other spot faces aft of the primary origin area. Beyond the slow-growth regions, the crack propagated relatively rapidly to a length of at least 12 inches aft of the forward end. Features associated with the more rapidly propagating portion of the fatigue region included relatively rough fracture features, crack arrest marks at up to 9.3 inches aft of the forward end, and wear between the fastener heads and the flange at distances up to 12 inches aft of the forward end. Subsequent to these findings the Federal Aviation Administration issued an Emergency Airworthiness Directive requiring fluorescent dye penetrant inspections of the wing attach flanges at intervals of 200 hours time in service.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The failure of the outboard right-wing lower attachment bracket due to fatigue cracking and the subsequent in-flight separation of the right wing assembly. Full narrative available
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