On June 11, 1995, an Air Tractor AT-301 (registration N23477) was involved in an aviation accident near Hoxie, KS. Investigators recorded the probable cause as: A loose nut (P/N 9294) on the adjusting screw for the number three cylinder, which prevented the exhaust valve from opening. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application flight, the engine sputtered and lost all power. The pilot performed a forced landing on a road, but the landing gear struck a ditch, causing the airplane to come to rest inverted. Postaccident examination found a loose nut on the number three cylinder's adjusting screw, preventing the exhaust valve from opening.
Accident Summary
The pilot was en route for an aerial application operation when the engine began to sputter approximately four miles after departure. According to the pilot, no abnormal indications were present on any of the engine instruments or the throttle quadrant. Shortly thereafter, the engine lost all power, forcing the pilot to initiate a forced landing on a road.
Forced Landing
During the landing, the airplane's landing gear struck a ditch, and the airplane subsequently came to rest in an inverted position. The pilot did not report any injuries.
Postaccident Examination
A postaccident examination of the engine revealed that the nut (part number 9294) on the adjusting screw for the number three cylinder was loose. This excessive clearance prevented the exhaust valve from opening, which likely caused the loss of engine power.
Probable cause
A loose nut (P/N 9294) on the adjusting screw for the number three cylinder, which prevented the exhaust valve from opening.