NTSB Identification: MIA02FA066.
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Accident occurred Wednesday, March 06, 2002 in Bunnell, FL
Probable Cause Approval Date: 01/24/2005
Aircraft: Cessna 172N, registration: N75908
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.
Witnesses stated that the accident airplane had just dropped a banner, and was being maneuvered from base to final, to execute a landing on runway 06 when the pilot made a radio communications transmission stating that aileron control had been lost. The airplane was observed at an altitude of about 200 to 300 feet, in about a 30-degree bank to the left, and the bank angle continued to increase as the airplane descended, disappearing from sight behind the treeline. The airplane impacted the ground nose-down, in a near vertical attitude, suspended by trees. Examination of the airplane showed that the aileron control cable was found to have separated between the bell crank in the left wing in the vicinity of the right upper doorpost pulley on its way to the control yoke. Corrosion was present on the upper left and right doorpost pulley bearing, the lower right doorpost pulley bearing, the bulkhead assembly-rear doorpost channel near the upper pulley, and the inner surface of the wing skins and ribs of both the left and right wings. The right wing forward flap cable was found to have separated about 27 inches from the bellcrank in the right wing, and corrosion was observed at the flap attachment rods and both the left and right attachment rods were bent. Sections a broken flap and aileron cables were examined at the NTSB Materials Laboratory, Washington, D.C., and the examination revealed that the wire rope of the flap cable was separated with almost all of the wires broken within a 0.5-inch axial length. There was minor unraveling of the strands adjacent to the separation, but no unraveling of the individual wires within strands. Detailed examination with a bench binocular microscope revealed extensive corrosion damage at the broken ends, with many of the individual wires corroded all of the way through. Dark deposits that appeared to be a mixture of oxidation debris and dried grease were noted within about 1 inch of the broken ends. The wire rope of the aileron cable had separated with almost all of the wires broken within a 0.5-inch axial length. There was some unraveling of the strands as well as the individual wires within strands adjacent to the separation. Detailed examination with a bench binocular microscope revealed extensive corrosion damage at the broken ends, with many of the individual wires corroded all of the way through. Dark and rust-colored oxidation deposits were noted within about 1.5 inches of the broken ends.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Inadequate maintenance inspection of the airplane by comapny maintenance personnel which resulted in corrosion in an aileron control cable going undetected, failure of the aileron control cable, and impact with terrain following loss of control of the airplane. Full narrative available
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