NTSB Identification: FTW93IA242.
The docket is stored in the Docket Management System (DMS). Please contact Records Management Division
Incident occurred Tuesday, August 17, 1993 in SAN ANTONIO, TX
Probable Cause Approval Date: 08/17/1994
Aircraft: CANADAIR CL-600-2B16, registration: N392PT
Injuries: 8 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 CREW EXPERIENCED AN UNCOMMANDED YAW TO THE RIGHT WHILE IN CRUISE FLIGHT AT FL410 WITH THE AUTO PILOT ENGAGED. A NORMAL LANDING WAS MADE WITHOUT INCIDENT AT THE INTENDED DESTINATION. EXAMINATION OF THE AIRPLANE'S RUDDER CONTROL REVEALED THAT THE SHAFT PORTION OF THE RUDDER QUADRANT WAS FRACTURED. METALLURGICAL EVALUATION OF THE FRACTURED SURFACE REVEALED THAT THE SEPARATION OF THE SHAFT PORTION WAS THE RESULT OF STRESS CORROSION CRACKING THAT INITIATED FROM OPPOSITE SIDES OF THE SHAFT AND PROGRESSED INWARD UNTIL ABOUT 60% OF THE SHAFT CROSS SECTION CRACKED DUE TO POOR CHOICE OF MATERIAL, IMPROPER RADIUS, AND EXCESSIVE TORQUE ON THE SHAFT NUT.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: THE FRACTURE OF THE RUDDER QUADRANT DUE TO STRESS CORROSION. A FACTOR WAS THE MANUFACTURER'S IMPROPER SELECTION OF MATERIAL. Full narrative available
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