Incident Overview
During the landing approach on an instructional flight, the certified flight instructor (CFI) initiated a go-around. Immediately afterward, the elevator control became partially jammed, first in a nose-low position and then in a nose-high position. Roll and yaw control were unaffected. The CFI applied considerable force to maintain airplane control and successfully landed without additional incident.
Post-Flight Inspection
Following the landing, the airplane was inspected. Investigators found evidence of mechanical binding in the elevator pitch control cables. Specifically, a screwdriver was discovered wedged between the nose gear actuator retract rod and the elevator control cables beneath the forward spar cover, located between and under the pilots' seats. When the nose gear retracted, the actuator rod moved the screwdriver against the elevator control cable, causing the binding. After the screwdriver was removed, elevator operation returned to normal.
Prior Maintenance
Two days before the incident, a contract mechanic had performed maintenance on the airplane. The work required removing the forward spar cover to access and replace a flap motor gearbox assembly and flap flex drives. Since that maintenance, the airplane had accumulated 5.8 flight hours before the incident occurred.
Conclusion
The incident was caused by a screwdriver left in the elevator control cable area during previous maintenance, which interfered with elevator pitch control when the nose gear retracted during the go-around.