On March 4, 2011, about 1830 eastern standard time, an Aeronca 7AC, N82429, impacted terrain after a runway excursion during takeoff at the Delphi Municipal Airport (1I9), Delphi, Indiana. The pilot was not injured. The airplane sustained substantial damage to the left wing and fuselage. The aircraft was registered to and operated by the student pilot under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight was originating at the time of the accident.

The pilot reported that he was conducting tailwheel proficiency work at the time of the accident. The proficiency maneuver involved adding engine power and increasing taxi speed until the tailwheel lifted off of the runway. At that point, engine power was reduced and the airplane slowed to a normal taxi speed. He stated that prior to the accident, he increased engine power for the maneuver and the airplane had rolled about 200 feet when the tailwheel lifted off the runway. He reduced the engine power to about 50-percent and began to allow the airplane to slow to taxi speed. At that point, a gust of wind caused the airplane to yaw to the right and depart the runway pavement.

The pilot elected to add full engine power in an attempt to takeoff from the grass area adjacent to the runway. However, the left main landing gear separated from the airframe and he decided to reduce the engine power to idle. The pilot was unable to maintain control when the airplane encountered a muddy area about 300 feet from the edge of the runway pavement. The left wing and fuselage were damaged. He noted that the flight controls operated properly during the event.

The grass area adjacent to the runway appeared uniform and graded. An examination of the area did not reveal any obvious ditches, ruts, or embankments prior to the soft, muddy area encountered after separation of the landing gear.

The forward landing gear attachment bolt was not recovered. The aft landing gear attachment bolt remained intact.

Wind conditions recorded at Purdue University Airport (LAF), located about 14 miles southwest of 1I9, at 1754, were from 180 degrees at 8 knots. At 1854, the winds were from 170 degrees at 7 knots.