Cessna 421C N619AC accident near Monroe, Louisiana

Probable cause

The failure of the maintenance personnel to properly reinstall the elevator trim tab hardware, which resulted in an in-flight separation of the elevator.

NTSB analysis

The pilot stated that, immediately after departure, he heard a loud pop and the control yoke oscillated violently. He declared an emergency and diverted to an airport with a longer runway and emergency services. The control yoke and airplane continued to oscillate until the airplane was on final approach, then the oscillation stopped. The pilot landed the airplane without further incident.

A postaccident examination of the airplane revealed that the right elevator had mostly separated from the horizontal stabilizer and only a small portion of the inboard elevator remained attached. There was a small puncture on the right side of the rudder, likely from the elevator impacting the rudder when it separated in flight.

The elevator trim push-pull tube remained attached to the trim actuator; however, there was no bolt, nut, or cotter pin attached to the aft fork connection, and the trim tab was missing. The push-pull tube did not exhibit any preaccident damage or anomalies. The remainder of right elevator and trim tab were not located. The elevator trim system was re-rigged two days before the accident. The maintenance personnel stated that they did not ensure that the push-pull tube hardware was reinstalled.

The load applied between the push pull tube and the trim tab held the bolt in place for 4 flight hours, and it’s likely that every time there was no load on the bolt it was able to move. Once the bolt finally backed out, the trim tab would have been free to move without control. It is likely that the freely moving trim tab resulted in the airplane oscillation and ultimately the in-flight separation of the elevator.

Text from the NTSB. Open the NTSB docket for CEN22LA202 for the full record.