On January 30, 2007, a Cessna 421 (registration N4584L) was involved in an aviation accident near Pocatello, ID. Investigators recorded the probable cause as: The separation of the bolt that attaches the elevator trim tab actuator rod to the elevator trim tab horn, resulting in violent flutter of the elevator, and eventually to the separation of the inboard half of the right elevator. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During climb, a bolt securing the elevator trim tab actuator rod to the trim tab horn came loose and separated, causing severe vibration and elevator flutter. The inboard half of the right elevator separated. The pilot used differential power to land safely.
Event Description
During the climb to cruise altitude, the bolt that holds the elevator trim tab actuator rod to the trim tab horn came loose from its retaining nut and separated from the aircraft. This led to severe airframe vibration, and eventually to violent elevator flutter. As a result of the flutter, the inboard half of the right elevator separated from the airframe.
Pilot Actions
By reducing power on the right engine and adding power on the left engine, the pilot was able to crab the aircraft, reduce the airflow over the right stabilizer/elevator, and ultimately execute an emergency full-stop landing.