CEN09LA526

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.

On August 16, 2009, at 1730 central daylight time, a Thrush Aircraft S2R-T660, N660RB, experienced a loss of elevator control and collided with the runway during a forced landing on runway 29 (5,506 feet by 100 feet, asphalt) at the Worthington Municipal Airport (OTG), Worthington, Minnesota. The pilot was not injured. The airplane sustained substantial damage to the right wing. The aerial application flight was being operated under Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from OTG at 1630. 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 airplane continued to climb and lose airspeed, and at an altitude of about 500 feet, it started to nose over. The pilot was able to level the wings and he added power to raise the nose. The pilot continued to control the pitch attitude of the airplane by adjusting engine power and elevator trim as he flew back to the airport to land. The pilot reported that the airplane became less controllable as the airspeed decreased, so he decided to land at a higher than normal airspeed. He reported that the airplane bounced when it touched down and he was not able to control the pitch attitude with the trim as it was ineffective due to the slow airspeed. The airplane bounced a second time, gaining about 30 to 40 feet in altitude. The pilot reported he closed the throttle and the airplane impacted hard on the runway, collapsing the main landing gear. The airplane slid approximately 200 feet and veered off the right side of the runway prior to coming to rest. A post accident examination of the airplane revealed the elevator push-pull rod had fractured. The fractured rod was examined by the Safety Board's Materials Laboratory. This examination revealed rod fractured at 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 fatigue fracture initiated initiated from both sides of the threaded shank on the rod end. The fatigue propagated from both sides of the cross section of the shank. 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 in at least three directions.