On August 12, 1994, at 1130 Pacific daylight time, an antique Perth Amboy Bird BK airplane, NC731Y, ground looped on landing at the Gillespie airport, El Cajon, California. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft sustained substantial damage to the lower outboard right wing. The certificated airline transport pilot and the one passenger on board were not injured. The flight originated at the Gillespie airport on the day of the accident at 1100 hours as a local area personal flight. In his written statement, the pilot reported that he performed a normal landing on runway 27 right. As the airplane slowed to about 15 mph, a "swirling gust of wind" lifted the tail and turned the airplane to the left. The pilot noted that at this slow speed the rudder and elevator were not effective and his efforts to counteract the left turn were not effective. The aircraft left the pavement and ground looped when the left main wheel encountered soft soil. The right wing contacted the ground and was damaged during the uncontrolled swerve.