Incident Overview
On April 8, 2011, at approximately 1620 central daylight time, a Cessna 560XL, registration N547CS, suffered a loss of elevator trim control while climbing after departure near Abbeville, Louisiana. The two airline transport rated pilots, the sole occupants, were not injured. The aircraft was registered to CitationShares Sales Inc., operating as CitationAir under 14 CFR Part 91 on a positioning flight.
Flight Details
The flight departed Louis Armstrong New Orleans International Airport (MSY) at 1450 en route to William P. Hobby Airport (HOU) in Houston, Texas. Visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan had been filed.
In-Flight Event
According to the captain, the takeoff and climb were normal until reaching approximately 23,000 feet. About 1,000 feet below their cleared altitude, both pilots noticed an abnormal feel in the controls. The captain verified the autopilot was still engaged. Approaching 23,000 feet, the pitch trim annunciator activated. When the captain disconnected the autopilot, the aircraft's nose pitched up abruptly. The captain attempted to reduce control forces using electric and manual trim, but the pitch trim wheel spun without effect or friction. The captain slowed the aircraft to the trimmed speed and executed the jammed elevator trim checklist. After notifying company dispatch, he declared an emergency with San Antonio International Airport (SAT) approach control. A controllability check showed no other issues, and the captain flew a long final approach to an uneventful landing at SAT.
Post-Accident Examination
A post-accident inspection of the elevator trim system revealed that the aft elevator trim cable had separated into two parts. The fractured cable was retained for further analysis. On June 16, 2011, the cable pieces were examined in Wichita, Kansas. The fracture occurred 11 inches from the roller chain that tracked through the elevator trim actuator. Scanning electron microscope examination showed fatigue failures in the individual wire strands, with slight wear observed at high magnification.
Corrective Action
The cable had been installed at the time of manufacture and had accrued 5,445.3 hours total time at the incident. Cessna Aircraft determined that a cable with improved rope wire material was required. On April 9, 2012, they issued Service Bulletin SB560XL-27-34, mandating replacement of the elevator trim cable with the new cable within 300 hours or 6 months of receipt.