Alert Extracted From:
AC No. 43-16A
Alert No. 316
November 2004

Cessna; Models 300/400; Improper Attachment of the Elevator Trim Tab Actuator; ATA 2731

The FAA Aircraft Certification Office (ACO) located in Wichita, Kansas, provided the following article.

Several reports of control failures on Cessna 300 and 400 series airplanes have been brought to the attention of the Small Airplane Directorate. The root cause of each accident/incident, involves the elevator trim tab actuator.

To ensure the integrity of the flight control system, 30 years ago, Cessna switched from a self-locking nut to a castellated nut with a cotter pin. In each of the six accidents/incidents highlighted, the actuator for the elevator trim tab was not connected. In five of six reports, the probable cause was determined to be maintenance errors.

The sixth incident lists the cause as undetermined, although 3 days prior to the accident the elevator trim actuator was overhauled.

These reports indicate the maintenance personnel failed to properly secure the trim tab actuator. More specifically, there appears to be a failure to install the required cotter pin to secure the assembly, or the use of a self-locking nut instead of the castellated nut and cotter pin called for in the maintenance manuals. Additionally, the flightcrews were faulted in several instances for not discovering the loose connection during preflight inspections.

This article is to highlight to the aviation community, the need to follow the maintenance manual, and to doublecheck all work.