Incident Overview
On January 12, 2014, at approximately 1615 central standard time, a Cessna 680 Sovereign, registration N531RC, experienced a failure of the left-hand elevator trim driveshaft. The aircraft was operated by CC Industries under 14 Code of Federal Regulations Part 91 as a flight test, with two flight crewmembers onboard who were not injured. Visual meteorological conditions prevailed for the flight, which originated from Chicago Executive Airport (KPWK) in Wheeling, Illinois.
Flight Event
According to the pilot, while climbing to 15,000 feet mean sea level, the autopilot disengaged and an autopilot disconnect chime sounded, accompanied by an "AP fail A-B" message. The flight crew decided to return to the departure airport. The pilot noted that extra force was required to push the airplane's nose down while attempting to slow the climb. He applied nose-down trim but felt no change; the elevator trim tab indicator showed full nose-down trim. The pilot subsequently landed the airplane without further incident.
Post-Flight Examination
During post-flight inspections, the operator tested the stabilizer trim through its full range of travel and found no discrepancy in the system. The elevator trim tab indicator displayed correctly across the stabilizer's range. The operator then contacted a Cessna Aircraft Company Service Center for troubleshooting. It was determined that the connecting pin linking the drive shaft to the left-hand elevator trim tab actuator had become dislodged.
History
The source notes that this type of failure—the dislodging of the Cessna 680 Sovereign elevator trim tab drive shaft pin—had occurred on two other occasions. Cessna Aircraft Company was in the process of proposing a change to the drive pin dimensions and the method of securing the pin, which was intended to prevent the pin from dislodging in the future.