Cessna 441, VH-NAX

The pilot of the Cessna Conquest reported that during the take-off roll, the aircraft started to rotate of its own accord at 70 knots indicated airspeed.

With what he thought to be full forward trim selected and full forward pressure on the control yoke, the aircraft continued to climb. The pitch attitude increased further as the landing gear and flaps were retracted. Approaching 4,000 ft, the pilot reduced power and was able to maintain level flight. After checking the aircraft controllability in the approach and landing configurations, the pilot returned the aircraft to the departure airfield for an uneventful, although overweight, landing.

The subsequent maintenance investigation found the spiral groove in the trim wheel that drove the trim indicator needle had a piece broken out of it. This caused the trim needle to stick in the take-off position. Maintenance personnel reported that the pilot later stated that during the climb he had attempted to trim in order to compensate for the pitch up. While doing so he felt a resistance in the trim wheel and assumed that the trim system had failed. Therefore, he stopped trying to operate it. The pin was stuck in the damaged groove section and had increased the force required to move the trim wheel. Had the pilot applied additional pressure to the trim wheel, he would have overcome the restriction and regained trim authority. However, as he was not aware of the cause of the increased resistance in the trim system, he elected not to do so in case this action aggravated the situation.

A major defect report was submitted to CASA.