Piper PA-34-220T N4145B accident near Minden, Nevada

Probable cause

The pilot’s improper preflight inspection of the stabilator trim position, which resulted in a porpoised landing. Contributing to the accident was the maintenance personnel’s improper maintenance of the stabilator trim shaft.

NTSB analysis

The pilot reported that the accident flight was the first flight since the airplane had undergone a recent annual inspection. During the preflight inspection, the pilot conducted a functional check of the stabilator trim with the electric trim control but did not visually verify the stabilator trim position. During the takeoff roll, the pilot noted an anomaly with the stabilator and aborted the takeoff shortly after rotation. During the landing, the airplane porpoised several times and the nose landing gear collapsed.

Postaccident examination of the airplane revealed that the stabilator trim wheel indicator was found in the full nose-down position. Flight control continuity was established from the cockpit flight controls to the respective flight control surfaces. Binding was noted when using the stabilator trim wheel and force was needed to rotate the stabilator trim control wheel to the natural position. The examination of the stabilator trim shaft revealed a lack of lubrication and excessive wear on the upper- and lower-barrel mount bearings.

The mechanic who conducted the annual inspection reported that no anomalies were noted with the flight controls or the stabilator trim controls. The mechanic reported that he moved the stabilator trim controls to the full nose up position, lubricated the stabilator trim shaft, and then ran the stabilator trim to the full nose down position. During the lubrication of the stabilator trim controls, the mechanic operated the controls while the apprentice lubricated the stabilator trim shaft. However, the apprentice who assisted in the annual inspection reported that he did not recall lubricating the stabilator trim controls.

The binding and lack of lubrication on the stabilator trim shaft indicated that the inspection and the lubrication was not conducted in accordance with the manufacturer’s maintenance manual. The anomaly noted in the stabilator by the pilot was likely the trim position being in the full nose-down position and not in the neutral position as per the pilot’s operating handbook.

Text from the NTSB. Open the NTSB docket for WPR24LA268 for the full record.