Incident Overview
A postmaintenance check flight ended with a forced landing after the throttle control became inoperative, leading to a partial loss of engine power. The pilot, accompanied by the operator's director of maintenance (DOM), was on the flight. According to the pilot's written statement, the throttle issue emerged while approaching to land. The pilot selected a tidal beach as a forced landing site but was unable to reach it, ultimately landing in shallow water short of the site. The airplane sustained substantial damage to the wings and fuselage.
Maintenance and Examination Findings
In a written statement to the NTSB, the DOM reported that prior to the flight, while troubleshooting a recurring complaint of low engine manifold pressure, he noticed that the castellated nut connecting the throttle linkage to the fuel control servo was loose. He removed the cotter pin, tightened the nut, and reinstalled the cotter pin.
A postaccident engine examination revealed that a self-locking nut was missing from the throttle linkage arm, resulting in the disconnection of the throttle cable. The DOM clarified that the missing locknut was not the same one he had tightened; it was located on the other end of the throttle linkage arm, approximately 2 inches from the castellated nut he had addressed. The DOM noted that he should have checked the security of the hexagon self-locking nut but did not. The hexagon self-locking nut was not recovered.