Accident Details
On May 31, 2018, at approximately 1115 central daylight time, a Thrush Aircraft S2R-H80, registration N6215P, sustained substantial damage during a runway excursion while taking off from runway 18 at a private airstrip near Parkin, Arkansas. The aircraft was registered to Mid Continent Aircraft Corp and operated by Air Aids, Inc., under Title 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed, and the flight was conducted without a flight plan. The local flight was originating at the time of the accident. The pilot was not injured.
Pilot Report
According to the pilot, during the takeoff roll, the right rudder pedal moved all the way forward. Because the airplane was equipped with toe brakes, once the pedal was fully forward against the material hopper, directional control could not be maintained. The pilot attempted to stop the airplane by using reverse pitch on the propeller, but the airplane departed the east side of the runway and struck a ditch.
Aircraft Examination
Post-accident examination of the airplane revealed that the rudder pedal adjustment mechanism consisted of a track that allowed the rudder pedal shaft to move fore and aft, with a detent pin that engaged holes in the track. The track was fitted with a safety stop bolt to prevent the rudder pedal shaft from traveling too far forward and exiting the end of the track. The track assemblies for both the left and right rudder pedals showed wear on the track and the stop bolt located forward of the most forward detent position. The right adjustment track had a semi-circular section worn completely through, matching the shape of the rudder shaft. This was consistent with the rudder shaft being stopped by the stop bolt rather than being locked in the forward detent position. It could not be determined how long the rudder system had been used in this manner.
Maintenance Records
Review of the airplane's maintenance records indicated that the aircraft had accumulated 991 hours in service as of its most recent annual inspection, dated December 29, 2017. The "Before Starting Engines" checklist in use at the time of the accident included the instruction "Rudder Pedals – ADJUST and LOCK."
Manufacturer Service Letter
On June 11, 2018, the airplane manufacturer issued Service Letter SL-AG-126, entitled "Rudder Pedal Mechanism Inspection," which detailed proper use, rigging, and maintenance of the rudder system, including the rudder pedal adjustment mechanism.