Thrush Aircraft Inc S2R-T660 N660RB accident near Worthington, Minnesota

Probable cause

A fatigue failure of the elevator push-pull rod which resulted in the pilot's inability to control the aircraft's pitch attitude while landing.

NTSB analysis

The pilot reported he heard and felt a “loud pop” at the end of a spray run and realized he did not have elevator control. The pilot controlled the pitch attitude using power and elevator trim as he flew back to an airport to land. The pilot decided to land at a higher than normal airspeed so he could maintain control of the airplane. The airplane bounced twice during the landing. During the second runway impact, the main gear collapsed. The airplane slid approximately 200 feet and veered off the right side of the runway prior to coming to rest and sustained substantial damage to the right wing. A post accident examination of the airplane revealed the elevator push-pull rod was fractured through the first full thread of the threaded shaft adjacent to the conical section. The remaining threaded section of the rod was threaded into the monoball spherical bearing fitting. A metallurgical examination revealed a fatigue fracture that initiated from both sides of the threaded shank on the rod end. Examination of the monoball bearing revealed several dents in the metallic bearing shield. The shape, size, and location of the dents and the deformation of the bearing shield were consistent with over-travel contact by the boss on the monoball bearing.

Text from the NTSB. Open the NTSB docket for CEN09LA526 for the full record.