What happened
During the final approach, approximately 10 to 15 feet above the runway, the pilot attempted to counter a nose-heavy tendency by applying nose-up pitch trim. However, the trim continued to move in the nose-up direction even after the pilot released the pitch trim switch. In response, the pilot applied power and forward pressure on the control yoke. The aircraft touched down on all landing gears and bounced slightly before the nose landing gear made contact, causing it to collapse.
The pilot had operated the aircraft for approximately 20 hours since purchasing it two months prior. During the previous several flights, the pilot had experienced the trim continuing in the direction of application on 8 or 9 separate occasions. Specifically, the trim had continued in a nose-down direction 6 times and in a nose-up direction 2 or 3 times. The pilot had been managing these occurrences by moving the control yoke and the pitch trim switch in the opposite direction of the unintended travel. On the day of the accident, the aircraft was at an avionics shop for work, but the pilot did not report the pitch trim issue to the personnel there.
The investigation
A post-accident examination of the electric pitch trim system showed that the rocker switches would intermittently stick in either the nose-up or nose-down position. Disassembly and testing of the pilot's electric pitch trim switch indicated that while the unit was electrically satisfactory, it suffered from intermittent mechanical sticking. Dirt and grime were found near the rocker switch assembly, and an examination revealed that the pivot point hole in one of the two switches was .001 less than the minimum specification. The pitch trim servo itself tested as operationally satisfactory.