This February 2008 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Piper Aztec. Injuries: 1 Fatal. Location: Sterling, Kan. Aircraft damage: Destroyed.
What reportedly happened: The pilot held an airline transport pilot certificate with a multiengine land rating, and a commercial pilot certificate with single-engine land and instrument ratings as well as several instructor certificates. At the time of the accident he had approximately 3,000 hours, including at least 500 in the previous six months. The pilot had a total of 1,320 hours in Piper Aztecs.
The airplane was in cruise flight at 6,000 feet MSL when it entered an uncontrolled descent. It hit the ground in a right wing low attitude. The airplane cartwheeled, hit a cow, and scattered components and debris over a distance of 668 feet.
Examination of both stabilators revealed extensive aft streaking, initiating along the forward rivet line, consistent with working or “smoking” rivets. Examination of the stabilator trim tab fittings exhibited little deformation and the inboard rivet faces had been knocked off. The stabilator trim pushrod was not attached. The securing nut and cotter pin used to secure the pushrod to the tab was missing. The lack of deformation to the trim pushrod is indicative that the securing nut backed out during flight. The stabilator trim bell-crank, left side, was loose within its attach point and exhibited significant freeplay. Disassembly revealed elongation of the attach hole. These observations indicate prolonged inadequate maintenance.
Probable cause: The loss of pitch control during cruise flight resulting from the separation of the stabilator trim actuator due to inadequate maintenance.
For more information: NTSB.gov