Accident Overview
A Cessna TU206G (registration C-FIHV, serial number U20606154) operated by Transport Canada as flight TGO954 from Hamilton, Ontario, to Burlington Airpark experienced an increasing nose-up pitch tendency during take-off rotation and initial climb. The pilot applied full nose-down trim, but the pitch-up continued, requiring excessive forward pressure on the control wheel to maintain an appropriate pitch attitude during climb-out and return to Hamilton Airport. The aircraft landed without further incident.
Maintenance and Rigging Errors
The flight was the first after replacement of the elevator trim tab actuator, which had reached its five-year calendar life. The aircraft maintenance engineer (AME) who performed the work had 15 years of licensing experience, mostly on large turbine and small jet aircraft. The removal and installation involved a multi-step procedure followed by 11 steps to rig the elevator trim system. The AME referred to the maintenance manual but encountered difficulties.
Two specific areas caused difficulty. First, the manual specified cable tension of 10–15 pounds at "average temperature for the area." The AME found this ambiguous, as other manufacturers provided temperature-specific graphs. He tensioned the cables to 12 pounds. Second, the trim tab travel limits (25° up and 5° down) were located in a different section. The AME misinterpreted these as aircraft pitch angles rather than tab movement, despite a warning on page 9-8: "Be sure trim tab moves in the correct direction... Nose down trim corresponds to tab up position." He adjusted the actuator so the tab moved from trailing edge 25° down to 5° up, instead of the required 25° up to 5° down. The take-off trim was mistakenly set at 10° down (nose-up) instead of 10° up.
Independent Inspection
A second AME was assigned to conduct an independent inspection as per Canadian Aviation Regulations Section 571 and Airworthiness Notice 1 C010. Before inspection, the first AME briefed him on the installation, difficulties, and manual references. The two worked together; the second AME inspected the cable run and corrected a cotter pin interference, then confirmed the tab was rigged as explained. The independent inspection failed to detect the misrigging because the second AME relied on the first AME's explanation, undermining the intent of the inspection.
Prior Occurrence
In 1998, the same Transport Canada base dispatched a Beech King Air 90 with a misrigged rudder control. The pilot found that applying rudder trim in the correct direction worsened the yaw. The trim tab was operating backward. During re-assembly, the AMEs had disregarded the maintenance manual's wording, interpreting the cockpit placard "RUDDER TAB" as referring to tab movement rather than aircraft nose direction. They rigged the tab to move left when the indicator moved left. This was not discovered during the required independent inspection or during about 15 flight hours. An internal investigation concluded the placard was misleading, and an Aircraft Services Service Bulletin modified it to read "NOSE LEFT < RUDDER TAB > NOSE RIGHT."
Conclusion
The AME who replaced the elevator trim actuator misinterpreted the travel limits, influenced by informal discussions about the King Air rudder trim placard following the prior incident. Those discussions gave credibility to the idea that control tab nomenclature refers to aircraft response rather than tab deflection. The independent inspection process was compromised by the second AME's reliance on the first AME's explanation.