West Linn, OR, USA
N13060
Taylorcraft BF12
The 67-year-old float equipped Taylorcraft crashed into a river following a wing lift strut separation. A witness reported that it appeared the airplane was going to land; however, just before touchdown it began to ascend and enter a left turn. The witness said that shortly after entering the turn, the airplane's left wing buckled and folded back against the fuselage. The airplane then entered an uncontrolled descent to impact with the water. Visual examination of the fractured wing strut attachment fitting showed substantial corrosion and pitting throughout the assembly. Further examination utilizing a scanning electron microscope (SEM) revealed that the left wing strut fitting fractured due to extensive corrosion followed by fatigue cracking. The lower side of the fitting had corrosion pitting that extended from the interior of the fitting completely through the thickness in some areas. The upper side of the fitting was also thinned due to corrosion. Several areas of the fracture surfaces showed oxidation consistent with progressive crack growth over an extended period of time, and fatigue features were found in areas not damaged by rubbing or corrosion. The most recent annual inspection was completed 2 months prior to the accident by the owner, who held an airframe and powerplant technician license. It was not determined which one of the two pilots, an airline transport pilot/certified flight instructor (also the owner of the airplane) seated in the left front seat or the airline transport pilot/certified flight instructor (CFI) seated in the right front seat, was manipulating the flight controls when the accident occurred.
HISTORY OF FLIGHT On July 28, 2007, about 1148 Pacific daylight time, a float equipped Taylorcraft BF-12, N13060, was substantially damaged following an uncontrolled descent into the Willamette River near West Linn, Oregon. The local flight was conducted under the provisions of Title 14 CFR Part 91. The two occupants, an airline transport pilot/certified flight instructor (owner and operator of the airplane) seated in the left front seat and an airline transport pilot/certified flight instructor (CFI) seated in the right front seat, were killed. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from Lake Oswego, Oregon, approximately 25 minutes prior to the accident. Visual meteorological conditions prevailed and no flight plan was filed. Multiple witnesses reported that the airplane was observed doing water landings prior to the accident. One witness reported the that the airplane was in a climbing left turn, approximately 100 feet above the water, when it abruptly pitched to a nose-low attitude and spiraled into the water. A second witness, who was driving a boat on the river, described that it appeared the airplane was going to land, however, just before touchdown it began to ascend and enter a left turn. The witness reported that shortly after entering the turn, which he estimated to be 40-50 degrees, the airplane's left wing buckled and folded back against the fuselage. PERSONNEL INFORMATION First Pilot (seated in the left seat): The First Pilot, age 80, held an airline transport pilot (ATP) certificate, commercial pilot certificate and flight instructor certificate. The pilot held a second-class airman medical certificate issued on April 27, 2007, and contained a provision that required the pilot to wear corrective lenses. Second Pilot (seated in the right seat): The Second Pilot, age 52, held an airline transport pilot (ATP) certificate, commercial pilot certificate, flight instructor certificate and multiple type ratings. The pilot held a first-class airman medical certificate issued on August 24, 2006, with no limitations. Both pilots held airplane single-engine sea ratings. It was not determined which one of the two pilots was manipulating the flight controls when the accident occurred. AIRCRAFT INFORMATION The float-equipped model BF-12 65, serial number 2786, was manufactured by Taylorcraft in 1941. The two-place airplane was powered by an 85-hp Teledyne Continental C-85 carbureted engine. Review of copies of maintenance logbook records showed an annual inspection was completed by the First Pilot (a certificated airframe and powerplant mechanic) on May 26, 2007, at a recorded tachometer reading of 3,090 hours, airframe total time of 5,445 hours and engine total time of 2,535 hours. WRECKAGE AND IMPACT INFORMATION Representatives from the Portland, Oregon, Federal Aviation Administration Flight Standards District Office reported that the main wreckage was located in about 4 feet of water near the shoreline of the river. The left wing assembly was located in the water about .25 miles west of the main wreckage. The onsite Safety Inspector reported the left wing lift struts remained attached to the wing assembly. The Safety Inspector reported that the lower lift strut attach bracket had "severed" from the fuselage. The inspector reported that approximately 70 percent of the parting surface of the lift strut attach bracket appeared to have been severely corroded. MEDICAL AND PATHOLOGICAL INFORMATION Autopsies were performed on both pilots. According to the autopsy reports, the cause of death for both pilots was attributed to traumatic injuries sustained in the accident. Forensic toxicology was performed on specimens from both pilots by the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. The toxicology reports stated no ethanol, carbon monoxide, cyanide or listed drugs were detected. Refer to the toxicology report contained in the docket for specific test parameters. TESTS AND RESEARCH The NTSB Materials Laboratory, in Washington, D.C., examined the left wing strut attachment fitting (Materials Laboratory Report 07-109). Visual examination of the fractured attachment fitting showed substantial corrosion and pitting throughout the assembly. The fractures were located mostly in line with the inboard ends of the two strut attachment slots. Further examination utilizing a scanning electron microscope (SEM) revealed that the left wing strut fitting fractured due to extensive corrosion followed by fatigue cracking. The lower side of the fitting had corrosion pitting that extended from the interior of the fitting through the thickness in some areas. The upper side of the fitting was also thinned due to corrosion. Several areas of the fracture surfaces showed oxidation consistent with progressive crack growth over time, and fatigue features were found in areas not damaged by rubbing or corrosion. ADDITIONAL DATA / INFORMATION On April 2, 2007, Taylorcraft Aviation, LLC issued Service Bulletin (SB) 2007-001; Wing Lift Strut Assembly Corrosion Inspection/Replacement. The actions specified by the SB outline procedures "...to inspect and detect any internal or external corrosion of the wing lift strut tube..." The SB was specific to the lower end of the forward and aft lift struts near the strut attachment fitting. Review of maintenance logbook records for the accident airplane disclosed no record indicating that SB 2207-001 was completed. On November 8, 2007, Taylorcraft Aviation, LLC issued Service Bulletin 2007-002; Inspection of wing strut attachment fitting part number A-A11 for cracks and corrosion. The actions specified by the SB outline procedures "...to inspect and detect any internal or external cracks or corrosion..." of the wing strut attachment fittings.
The corrosion, fatigue fracture, and subsequent separation of the left wing lift strut attachment fitting. Also causal was the inadequate maintenance and annual inspection by the owner/pilot/mechanic.
Source: NTSB Aviation Accident Database
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