NTSB Identification: SEA97IA219.
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Scheduled 14 CFR operation of CONTINENTAL AIRLINES
Incident occurred Saturday, September 27, 1997 in SEATTLE, WA
Probable Cause Approval Date: 04/15/1999
Aircraft: Boeing 737-3T0, registration: N13331
Injuries: 134 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 reported that at liftoff, 'considerable aileron and rudder input' was required to maintain straight and level flight, and that when aileron input was reduced to zero, at least 5 units of left rudder trim was required to maintain wings-level flight. The crew returned to the departure airport and landed without further incident. Postflight troubleshooting revealed that the ABSB-4 right aileron bus cable was broken and the ABSA-4 right aileron bus cable was frayed, both where the cables ride over the right wing/body joint aileron pulleys. Examination of the cables at the NTSB materials laboratory concluded that the ABSB cable failure was the result of severe internal wear due to normal movement of the cable over a pulley for an extended period of time. Examination also noted several areas of severe external wear on the cables. The airplane maintenance manual, which specifies inspection of exposed cables at each 'C' check (approximately once per year), contains procedures for checking cables for broken wires and gauging the extent of external wear. An 'optional as needed' step also specifies cable replacement based on reduction of cable cross sectional area. The airplane received a segmented 'C' check, which included inspection of aileron cables, approximately 6 weeks prior to the incident.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Separation of the ABSB-4 aileron bus cable, resulting in reduced lateral controllability of the aircraft. Related factors were wear in the cable and inadequate inspection of the cable by company maintenance personnel. Full narrative available
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