Kissimmee, FL, USA
N453WA
North American SNJ-6
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.
HISTORY OF FLIGHT On May 9, 2005, at 1620 eastern daylight time, a North American SNJ-6, N453WA, registered to and operated by Warbird Adventures Incorporated, came apart in-flight while performing aerobatics near Kissimmee Gateway Airport, Kissimmee, Florida. The introductory flight lesson was operated under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual meteorological conditions prevailed at the time of the accident. The airplane was substantially damaged. The certified flight instructor and the pilot rated student were fatally injured. The flight departed Kissimmee Gateway Airport on May 9, 2005 at 1600. According to Warbirds Adventures Incorporated, the purpose of the flight was to familiarize the pilot rated student with the airplane within a 30-minute flight lesson. During the flight lesson the certified flight instructor demonstrated various flight and aerobatic maneuvers. Witnesses on ground reported seeing the airplane executing a series of aerobatic maneuvers. Witnesses further observed the airplane enter a spin, and descended rapidly and collided with ground. The downed airplane was located 19.2 miles south from the Kissimmee Gateway Airport. PERSONNEL INFORMATION Review of pilot records revealed that the certified flight instructor was issued a private pilot certificate (foreign based) on August 7, 1995, with ratings for airplane single engine land, and glider self launch. The certified flight instructor received his commercial pilot rating on January 1, 2001, with ratings for airplane single engine, multiengine, and instrument ratings. The certified flight instructor received his flight instructor rating for airplane single engine on July 24, 2003. Review of medical records revealed the certified flight instructor held a second-class medical certificate issued on June 30, 2004. Review of company records indicated that the pilot accumulated a total of 1777.8 flight hours in the T-6/SNJ, and a total flight time of 6469.5 flight hours. Review of pilot records revealed that the private pilot was issued a commercial pilot certificate update on November 29, 2004, with ratings for airplane single engine, multiengine land, and instrument airplane. The commercial pilot held a second-class medical certificate issued on October 4, 2004, with restrictions for wearing corrective lenses for near and interim vision. Records revealed the commercial pilot's recorded flight time was approximately 4000 flight hours. AIRCRAFT INFORMATION Review of the maintenance logbooks revealed that the last recorded annual inspection was conducted on February 23, 2005.The recorded Hobbs time at the time of the inspection was 2225.0, and the airplane total time was 7580.6. On April 25, 2005 a 100-hour inspection was performed on the airframe. The recorded Hobbs time at the 100-hour inspection was 2320.5, and the airplane total time was 7742.3. The transponder test and inspections were performed on April 29, 2004. Review of the engine logbooks revealed that the engines 100-hour inspection was performed during the airframe annual inspection on February 23, 2005. The engine total time at the 100-hour inspection was 7646.8, and the time since major overhaul was 1164.1. Review of maintenance records revealed that on May 20, 2001 the right-hand side top wing attach angle bracket was replaced. The right-hand wing center aileron hinge was reinforced, and the right elbow panel was replaced and all nut plates were replaced with new machine screws. METEOROLOGICAL INFORMATION The nearest weather reporting facility at the time of the accident was Kissimmee Gateway Airport, Kissimmee, Florida. The 1646 surface weather observation was: sky scattered, visibility 10 statue miles, temperature 82 degrees Fahrenheit, dew point temperature 53 degrees Fahrenheit, wind 180-degrees at 8 knots, and altimeter 30.02. WRECKAGE AND IMPACT INFORMATION Examination of the accident site revealed, the airplane was located in a dense wooded area 19.2 nautical miles on the 195-degree radial from the Kissimmee Gateway Airport, Kissimmee, Florida. 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-foot 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. The right aileron was also located approximately 0.13 nautical miles on a 048-degree heading from the main wreckage site. The odor of fuel was present at the wreckage site. The engine assembly was located at the base of the crater with the propellers still attached at the hub. The propellers displayed chord-wise scoring, and the blades were bent aft. Post accident examination of the airframe revealed, the main fuselage, center wing structure and cockpit section of the airplane were crushed. All flight controls, navigational instruments, and radios were crush and broken. All cockpit flight controls were crushed. Post accident examination of the left wing assembly displayed accordion crush damage to the skin of the leading edge of the wing. The left wing assembly was fragmented. The left aileron flight control cables were separated, and broken at multiple points throughout the airframe. Cable turnbuckle ends were attached to the aileron attachment fittings, and the cable ends were broken. The left main landing gear assembly was separated from the left wing assembly, and displayed deformation damage. Post accident examination of the right wing revealed it was separated from the center wing structure of the airplane. The separation break was at the lower and upper angle brackets. Mid-span on the right wing there was an approximately a 45-degree buckle from the leading edge to the trailing edge of the wing. The right aileron was separated from the wing assembly and broken into two separate parts. The right main landing gear was separated from the wing assembly, and displayed deformation damage. The right wing aileron flight control cables were broken from the bell cranks, and the cables were separated at multiple points within the wing. The aileron cables were broken at the separation points. Post accident examination of the vertical and horizontal stabilizer revealed crush damage to both flight surfaces. The elevator surfaces were separated from the horizontal stabilizer, and crush damaged. The rudder was separated from the vertical stabilizer, and crush damaged. Rudder and elevator cables were located in the empennage section and broken at the separation points. The elevator cables were cut for extraction, and located in the empennage section. Post accident examination of the engine revealed, all nine cylinders were crush damaged. The push rod tubes, and rockers covers were crush damaged. The nose case of the engine was separated from the power section and sustained crush damaged. The supercharger section was crush damaged. The accessory section, all attaching hardware and accessories were broken and crush damaged. PATHOLOGICAL INFORMATION The District 10 Medical Examiners Office of Florida preformed the postmortem examination of the Certified flight instructor on May 12, 2005. The cause of death was blunt force trauma. The postmortem toxicology specimens from the pilot were negative for carbon monoxide, cyanide, drugs and alcohol. The District 10 Medical Examiners Office of Florida preformed the postmortem examination of the commercial pilot on May 12, 2005. The cause of death was blunt force trauma. The postmortem toxicology specimens from the pilot were negative for carbon monoxide, cyanide, drugs and alcohol. TEST AND RESEARCH In the SNJ-6 wing attachment structure design, four "L"-shaped flanges are fastened to the external surface of the wing skin for each wing, and four other "L"-shaped flanges are fastened to the external side of the wing carry-through skin on each side of the fuselage. The lengthwise directions of the flanges are oriented with the chordwise plane of the wing joint with one (horizontal) leg of the flange fastened to the skin and the other (vertical) leg protruding outward. On each side of the joint, one flange is located at the upper surface, one is located at the leading edge, and two (one forward and one aft) are located at the lower surface. The flanges are fastened at the wing joint by attach bolts with a panel between the flanges. Once assembled on the airplane, a fairing covers the joint. 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. Additional relatively 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. The National Transportation Safety Board Materials Laboratory examination of the lower surface areas adjacent to the fatigue origins showed little evidence of corrosion, and no noticeable pitting was observed at the fatigue origin areas. All fracture features were transgranular, with no evidence of intergranular attack. In areas outside of the flat fatigue regions, the fracture surface had dimple fracture features. On the fractured lower attach flange, a crack was observed in the lower surface of the inboard (horizontal) leg of the flange at the forward side of the fastener. A recess was observed corresponding to the diameter of the head. The crack was present near the forward edge of that recess, but the crack did not intersect the fastener hole. Additional fasteners from the inboard leg of the lower attach flange forward end of the lower attach flange were removed, and the flange was cut to facilitate the opening of the crack. The crack was opened in upward bending. The crack was approximately 0.005 inch deep. The fracture had a somewhat rough irregular appearance and was at an angle to the lower surface. Fracture features were covered by non-conductive deposits or oxidation. No features consistent with fatigue were observed. Areas of the flange around the other row fasteners were examined using optical microscopy, and no other cracks were observed. ADDITIONAL INFORMATION Review of the operational records for The Warbird Adventure vintage aircraft flying school revealed, the pilot duty description were as follows: Fly customers in accordance with company procedures and provide a safe and enjoyable experience. Permitted maneuvers and operations: (Recommended order of execution) aileron rolls, loops, reverse Cuban- 8's, regular Cuban-8's, barrel rolls, immelmans, split-s, hesitation rolls, wingovers, and cloverleaves. The Federal Aviation Administration issued Emergency Airworthiness Directive (AD) 2005-12-51 on June 08, 2005. AD 2005-12-51 requires fluorescent dye penetrant inspections of the wing attach flanges at intervals of 200 hours time in service. The inspection method described in AD 2005-12-51 should be capable of detecting relatively small cracks that are still growing relatively slowly. The wreckage of N453WA and all of its components were released to CTC Aviation Services LAD Incorporated on August 8, 2005.
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.
Source: NTSB Aviation Accident Database
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