On February 21, 2012, about 1715 central standard time, a Cessna 180H, N3SM, ground looped during landing on runway 14 at Lone Star Executive Airport (CXO), Conroe, Texas. The airline transport pilot (ATP) and a private pilot were uninjured. The airplane sustained substantial damage to the left wing spar, left elevator, and stabilizer. The airplane was registered to and operated by the (ATP) pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan had not been filed for the local flight that departed from CXO about 1630. The right seat pilot held an airline transport pilot and flight instructor certificates and was a friend of the left seat pilot who held a private pilot certificate. The right seat pilot had a tailwheel endorsement. The left seat pilot did not have a tailwheel endorsement. The right seat pilot said that they departed on a personal flight that remained in the local area. About 45 minutes after departure, they returned to CXO to practice landings. The left seat pilot performed the first landing and subsequent takeoff, which was "normal." During the second landing by the left seat pilot, the airplane veered "sharply" off the runway centerline. The right seat pilot took the controls from the left seat pilot and was unable to regain directional control of the airplane. The left wingtip contacted the runway, and the airplane ground looped.