The company's task cards indicated that the mechanic failed to lockwire the drive stop coupling bolts to the drive stop, despite noting that the work had been completed by stamping the card with his designation. The mechanic responsible for installing the lockwire was under stress due to family issues at the time of the varicam was last serviced.
The resulting feedback in the cockpit was an uncommanded aft movement of the control yoke, which placed the airplane in a pitch-up attitude that could not be corrected by flight control inputs from the cockpit. This resulted in the deformation of the left side varicam and subsequent upward deflection of the left elevator, which is hinged to the varicam. When the flight crew adjusted the varicam trim during the initial climb, the absence of this bolt prevented a section of the drive shaft from rotating, allowing only a portion of the varicam to move. Because the varicam likely did not display any deformation before takeoff, as it would have been inspected after the previous flight, the bolt likely backed out sometime during the takeoff. Postaccident examination revealed that maintenance personnel had failed to secure the drive stop coupling bolts with lockwire and that one of the bolts had backed out of its bolt hole. This secondary control surface is directly connected to the elevators and provides a primary structural load path for all elevator loads thus, any damage to the varicam was considered substantial. Using coordinated inputs, the flight crew was able to land the airplane without incident.Ī postlanding examination revealed that the variable camber, or varicam, was damaged during the event. The flight crew attempted to regain pitch control by adjusting the trim wheels, but the airplane continued to maintain a pitch-up attitude. During the airplane's climb, the airline transport pilot, who was acting as pilot-in-command, adjusted the trim to reduce nose-down pressure and subsequently observed an uncommanded aft movement of the control yoke and simultaneous increase in the airplane's pitch attitude. The company dispatched the accident airplane to a fire as part of an exclusive contract with the United States Forest Service and under the direction of the Bureau of Land Management. Defining Event: Flight control sys malf/fail
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