NTSB Identification: ATL04LA143.
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Accident occurred Tuesday, July 20, 2004 in Winder, GA
Probable Cause Approval Date: 09/13/2005
Aircraft: Cessna 172S, registration: N2069S
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot stated that, while in cruise flight, he noticed the airplane required a greater than normal amount of right rudder input to maintain coordinated flight. During landing, when the nosewheel touched down, the airplane decelerated rapidly, veered uncontrollably to the right, and nosed over. Examination of the runway revealed a single, wide black skid mark was extended from near the runway centerline to where the airplane came to rest inverted. Examination of the airplane revealed the upper torque link bolt was fractured with a separated portion of the bolt lodged in the torque link assembly. The bolt showed shear deformation adjacent to the fractures consistent with shear overstress. The lower torque link bolt and the connecting bolt also showed shear deformation. Microhardness testing of samples taken from the bolts revealed the material complied with the manufacturer's specifications. Examination of the forward face of the stop lug on the upper torque link revealed deformation from multiple impacts on the forward face. The airplane had accumulated 81.4 hours since new. The pilot stated the airplane's nose strut had been serviced twice since April 2004, because the nose strut visually appeared low. The mechanic who serviced the strut the day before the accident stated he added nitrogen to the strut to effect a strut extension of approximately two and a half inches, and he moved the strut up and down to check for bottoming out, over service, and a return to static extension of approximately two and a half inches. The airplane was flown for two approximate one-hour flights since the strut service. A review of the Cessna Aircraft Company Model 172 Maintenance Manual, Page 301, "Nose Landing Gear Shock Strut - Servicing," revealed Section 2. B. (8) states: "With strut fully extended and nose wheel clear of ground, inflate strut to 45 psi."
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The improper maintenance (over-pressurization) of the nose gear strut, which resulted in an overload failure of the nose gear upper torque link bolt. The airplane subsequently nosed over during an uncontrollable landing roll. Full narrative available
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