Accident Details
On June 26, 2013, at approximately 1825, an Air Tractor AT-301, registration N3168X, experienced a loss of engine power and made a forced landing into a field near Colome, South Dakota. The aircraft was operated by Semper Fi Aviation LLC under 14 Code of Federal Regulations Part 137 as an aerial application flight. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight had originated from Winner Regional Airport (ICR) in Winner, South Dakota, about 1720.
Pilot Account
The pilot reported that during the start of his third spray pass, after clearing telephone wires on the southwest corner of the field, he entered the field at an indicated airspeed of 95 knots. Engine instruments showed 33 inches of manifold air pressure (MAP) at 2,100 rpm. He immediately noticed a reduction in power. When he attempted to pull back on the control stick to gain altitude, the airplane's tail and right wing struck the field. During the forced landing rollout, the right landing gear collapsed, and the airplane rolled onto its nose.
Post-Accident Inspection
An airplane and powerplant-rated (A&P) mechanic ran the engine while it was still attached to the airframe. The mechanic operated the engine at 32 inches of MAP at 2,100 rpm, then reduced power to 30 inches of MAP. He was unable to run the engine at full power (36 inches of MAP at 2,200 rpm) due to vibration from the bent propeller and collapsed landing gear. The mechanic reported that the engine ran normally without anomalies. No water was found in the fuel system, and weather conditions were not conducive to carburetor icing.