NTSB Factual Report

On July 20, 2004, at 1715 eastern daylight time, a Cessna 172S, N2069S, registered to Aerocraft Holding Co., LLC, and operated by WK Dickson & Co., Inc., veered right and nosed over during landing at the Winder Barrow Airport, Winder, Georgia. The business flight was operated under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual meteorological conditions prevailed. The private pilot was not injured, and the airplane sustained substantial damage. The flight departed Cherokee County Airport, Canton, Georgia, about 1640 on July 20, 2004.

The pilot stated his takeoff from Canton, Georgia, was normal. He stated that, while in cruise flight, he noticed the airplane required "a greater than normal amount of right rudder" input to maintain coordinated flight. The pilot stated he executed a left visual traffic pattern for runway 31 at Winder, Georgia. The pilot stated he utilized full flaps and slowed to 65 knots on final approach, and the airplane touched down normally on the main wheels. The pilot stated that, when the nosewheel touched down, the airplane decelerated rapidly and turned to the right. The pilot stated he initially applied rudder to correct the turn, but then quickly applied the brakes "as it was apparent something was wrong with the operation of the nose gear." The airplane continued to veer right until it was facing perpendicular to the runway, and it nosed over at the runway edge.

Examination of the runway revealed a single, wide black skid mark was observed extending from near the runway centerline to the right side of runway 31 where the airplane came to rest inverted. Examination of the airplane revealed damage to the wings, empennage, and nose gear. Examination revealed mechanical continuity from the cockpit rudder pedals to the rudder and to the nosegear steering assembly.

The nose gear upper and lower torque links and attachment bolts were removed from the airplane and forwarded to the National Transportation Safety Board (NTSB), Office of Research and Engineering, Materials Laboratory Division, Washington, D. C., for examination. Examination revealed the upper torque link bolt was fractured with a separated portion of the bolt lodged in the torque link assembly. The fracture surfaces on the bolt were flat, and the bolt showed shear deformation adjacent to the fractures consistent with shear overstress. The direction of the shear deformation on the bolt was primarily upward along the length of the upper torque link. The upper torque link spacer through which the bolt passes was deformed, and the opening of the bolt hole was elongated on one side.

Examination of the lower torque link bolt revealed shear deformation in locations similar to the areas where the upper torque link bolt was deformed. The connecting bolt that holds the two torque links together showed shear deformation. The deformation coincided with the area of the connecting bolt that passes between the edges of the bolt hole in the upper torque link and the interior edges of the bolt holes in the clevises of the lower torque link. Microhardness testing of samples taken from the upper and lower torque link bolts and the torque link connecting bolt revealed the material complied with the manufacturer's specifications.

According to the NTSB Materials Laboratory report, "deformation was observed on the forward face of the stop lug on the upper torque link. There was evidence of multiple impacts on the forward face ... which formed lips on the top and bottom edge of the face." The report included an illustration that showed the top and bottom edges of the forward face of the stop lug were displaced outward due to "deformation from the multiple impacts."

The airplane was manufactured in 2004 and had accumulated 81.4 hours at the time of the accident. The owner of the airplane stated it was purchased in April 2004, and it had approximately 45 to 50 hours on it when purchased. The owner stated there have been no reports of any hard or abnormal landings with the airplane. The pilot stated the airplane's nose strut had been serviced twice since April 2004, and the service was requested because the nose strut visually appeared low. A review of the maintenance logs revealed one record of service; an entry dated July 19, 2004, stated "serviced nose gear strut with nitrogen." The pilot stated the airplane was flown for two approximate one-hour flights since the last service and prior to the accident.

The airframe and powerplant mechanic who serviced the strut on July 19, 2004, stated there was no evidence of a hydraulic leak, and he added nitrogen to the strut to produce an extention of approximately two and a half inches. He stated the "generally accepted industry practice is the width of three fingers." He stated he moved the nose strut up and down to check for "bottoming out or over service" and to check for return to the static extention of approximately two and a half inches.

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."

A review of Service Difficulty Reports on file with the Federal Aviation Admistration revealed one report of a problem with the nose landing gear shock strut of a Cessna 172S that had accumulated 31 hours since new. Report No. OMB 2120-0003 stated, "strut leaked down ... . Upon evaluation, discovered [the strut] ... to be practically empty of fluid."

NTSB Probable Cause

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.