OT Safety Bulletin

Runaway Trim

Reviewing some recent General Aviation reports highlighted that in some cases pilots need to be ready to recognise and act promptly in the event of a runaway trim. Some aircraft types require a quick response to prevent a loss of control. Therefore, if you are not sure what your aircraft’s pilot operation handbook/ flight manual says about this go and refresh your memory. Understand the system, and what to do if it goes wrong.

A UK AAIB report noted:

Pilot knowledge and awareness of trim runaway – safety message

The FAA research, other previous events, and findings from this investigation, indicate that a pilot’s familiarity with the autopilot and trim system could reduce the time to recognise and effectively respond to a potentially hazardous trim runaway condition. This could include, for each aircraft type to be flown:

• System knowledge of the electric trim and autopilot, and the associated normal and abnormal operating procedures
• Carrying out the relevant pre-flight checklists for the autopilot and trim systems – being aware that they may be separate to the main pre-flight procedures
• Awareness of the indications of a trim runaway – remembering that the indications may not be ‘direct’
• Appreciation of the significance of the control forces which may be required to control the aircraft in the event of a trim runaway, particularly for a single pilot
• Awareness of the corrective actions for a trim runaway – for example, how to locate and open the appropriate circuit breaker, and other possible ways to override or disable the system.

An In Focus Special issue on handling a trim runaway can be downloaded from the UK CAA website.

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