On November 7, 1997, at 1715 central standard time (cst), a Cessna 421A, N2957Q, operated and owned by an airline transport pilot, sustained an in-flight structural failure of the right horizontal stabilizer trim tab assembly, while on climb out from Tomahawk Airport, Tomahawk, Wisconsin. The pilot reported no injuries. The flight, conducted under 14 CFR Part 91, originated at Tomahawk, Wisconsin, at 1700 cst, with an intended destination of Poplar Grove, Illinois. An IFR flight plan was filed, and visual meteorological conditions prevailed at the time.

In the pilot's written statement, he reported that climbing through 11,000 feet at 700 feet per minute rate of climb, on autopilot, he heard a "loud bang..., followed by the disconnect of the a/p [autopilot], a rapid vibration in the control yoke and a pitch down of the aircraft nose." The pilot said he slowed the aircraft down and confirmed that both engines were running properly. When he further slowed the aircraft to 130 miles per hour it "...did not stop or change the vibration." He said pitch trim was not available. The pilot reported his situation to Air Traffic Control and landed without further incident at Merrill Municipal Airport (RRL), Merrill, Wisconsin.

Examination of the aircraft by the Federal Aviation Administration revealed extensive damage confined to the right elevator and trim tab. Ribs 1, 2, and 3 of the elevator had substantial separation damage and the elevator spar was severed at the 2nd rib. The examination revealed that the rear trim tab linkage bolt was missing. There was little damage to the yoke or trim tab bushing. The trim tab bushing moved freely. The forward trim tab linkage bolt was found intact and the trim tab linkage was not binding. An undersized cotter pin was found in the forward linkage bolt.

The trim tab actuator arm was found to be bent 90 degrees. There was paint transfer to the trim tab from the elevator and transfer damage to the trim tab from the linkage. The trim tab hinge was intact and free moving.

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