NTSB Identification: ATL04IA138.
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Incident occurred Tuesday, May 11, 2004 in Chamblee, GA
Probable Cause Approval Date: 04/28/2005
Aircraft: Cessna 172RG, registration: N6562V
Injuries: 2 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The certified flight instructor reported full nose-down elevator deflection could not be achieved in cruise flight. The flight returned to the airport and landed without further incident. Examination revealed the threaded shaft of the nose gear steering bungee assembly was fractured, and the damaged component physically restricted the movement of the elevator control assembly. Metallurgical examination of the shaft revealed fatigue fractures in two locations with no evidence of hardness anomaly and no evidence of improper lubrication. Examination of the profile of the thread relief area of the shaft revealed the region was irregular and asymmetric, and a number of machining grooves were of smaller radii than the 0.050-inch radius specified in Cessna technical drawings. The shaft was absent of identifying markings or a part number, and maintenance logs for the airplane revealed no record of repair or replacement of the component. Federal Aviation Administration Airworthiness Directive (AD) 81-14-06 for the Cessna 172RG requires the replacement of part number 2467003-1 rudder trim/nose gear steering bungee with part number 2467003-6 rudder trim/nose gear steering bungee. Cessna Service Letter SE 80-99 states the new steering bungee part number 2467003-6 "includes a larger diameter jack screw shaft providing substantially greater unit strength and longer service life." Both the AD and the Service Letter are applicable to Cessna 172RG airplanes serial numbers 172RG0001 through 172RG0769. The incident airplane was serial number 172RG0775.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The fatigue fracture of the nosewheel bungee assembly, which restricted the movement of the elevator control. A factor was the inadequate equipment from an unknown source/manufacturer. Full narrative available
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