19990331003129A

Pilot lost control of the acft on landing, and the acft struck a concrete post with the left wing, a tree with the right wing, and a ditch with the tail wheel, other circumstances are unknown. (.19) on March 31, 1999, at 1730 central standard time, an air tractor AT-301 agricultural airplane, N8789S, was substantially damaged upon collision with a post while landing near Garwood, Texas. The instrument rated commercial pilot, sole occupant of the airplane, was not injured. The airplane was registered to and operated by anf air services inc., of Garwood, Texas. Visual meteorological conditions prevailed for the title 14 CFR part 137 flight for which a flight plan was not filed. The local flight originated from the operator's private airstrip approximately 30 minutes prior to the accident. The operator reported to the FAA inspector, who responded to the accident site, that after a normal landing and roll out, the pilot initially applied brake pressure to slow down the airplane's landing roll. The pilot reported that when he attempted to re-apply brake pressure, the right brake pedal "fell all the way to the floorboard" resulting in a loss of directional control. The airplane came to a stop after the left wing impacted a concrete pole located on the west side of the airstrip. Examination of the airplane by the FAA inspector revealed structural damage to the left wing spar and the empennage. The inspector further stated that the failure of the right brake was due to the separation of the threaded rod connecting the brake master cylinder to the top portion of the rudder pedal. The inspector added that the jam nut was found still attached to the rod. (.4) the commercial pilot lost control of the agricultural airplane during the landing roll following the failure of the right wheel brake system. The pilot initially applied brake pressure to slow down the airplane's landing roll. When the pilot attempted to re-apply brake pressure, the right brake pedal 'fell all the way to the floorboard.' The airplane made a gradual left turn, which the pilot could not compensate for with an inoperative right brake. The left wing impacted a concrete pole located on the west side of the airstrip. The FAA inspector stated that the failure of the right brake was due to the eye bolt, which connects the brake master cylinder to the top portion of the rudder pedal, pulling out to the master cylinder. The operator stated that the only possible way for the eye bolt to become separated from the master cylinder was for the eye bolt to 'pull out' of the threaded hole in the brake master cylinder. The operator reported that the time in Service for the failed part was unknown. He added that the bottom 2 or 3 threads of the eye bolt appeared to be damaged or stripped, which 'could have resulted in the eye bolt pulling out' of the cylinder. (-23)on landing rollout, the right brake master cylinder became disconnected from the master cylinder clevis where it attaches to the right rudder pedal. The clevis screws into the master cylinder and has a jamb nut to lock into place. When the clevis seperated from the master cylinder, the rudder pedal bacame ineffective for braking. With only the left brake working, the aircraft exited the runway to the left striking a concret post with the left wing, a tree with the right wing and a ditch with the tailwheel assembly. The wings remained intact but serious spar damage occurred. The epenauge also received cracks in the structural tubing. The aircraft had an ann ual inspection 24.0 hours prior. According to maintenance records entries, no work was accomplished on the master cylinder assemblies.