On November 7, 2014, at 0900 mountain standard time, a Champion 7AC, N84462, impacted a farm field and wheeled sprinkler system, 10 miles south of Darby, Montana. The commercial pilot and single passenger were seriously injured, and the airplane was substantially damaged. The airplane was registered to the pilot and operated under the provisions of 14 Code of Federal Regulations, Part 91. Visual meteorological conditions prevailed for the personal flight, and no flight plan had been filed. According to the pilot he was attempting to land on a private grass airstrip in a farm field surrounded by mountainous terrain when the accident occurred. Witnesses observed the airplane descending at an estimated 90 degree right-wing-low bank angle; the wings then leveled before impacting the ground. The pilot stated that due to injuries he could not recall all the events leading up to the accident; however he recalled observing a TV interview of a witness after the accident, in which the witness stated that it was windy at the time of the accident. The nearest weather reporting station was 40 nautical miles north of the accident site and reported wind from 230 degrees at 4 knots. The pilot reported light and variable winds with 5-10 knot gusts at the time of the accident; however he stated that he has experienced unexpected severe gusts and terrain induced turbulence pass through the area momentarily followed by complete calm. The pilot rated passenger in the rear seat recalled that he felt what he believed to be wind shear or a down draft before impact. Post-accident examination of the airplane did not reveal any failures or malfunctions with the airplane that would have precluded normal operation. Further examination revealed that an undetermined amount of aviation fuel was recovered from the fuel system. It was also noted that the airplane was not equipped with flaps or a stall warning system.