On August 4, 1999, at 1304 mountain daylight time, a Cessna 170B, N4448B, sustained substantial damage when it departed the right side of the runway during landing roll at Natrona County International Airport, Casper, Wyoming. The commercial pilot/flight instructor and student pilot/passenger were not injured. The flight was operating under Title 14 CFR Part 91 and no flight plan was filed. Visual meteorological conditions prevailed for this personal flight which originated from Knoxville, Iowa, at 1000 central daylight time. At the time of the occurrence, the pilot/flight instructor was occupying the right seat and the student pilot/ passenger was occupying the left seat. According to the pilot, she was cleared to land the aircraft on runway 03 and the ATIS reported the wind to be from 070 at 12 knots with gusts to 18 knots. The pilot said that near the end of the landing roll the plane started to swerve to the right and she applied left brake. She said the left brake "went to the floor and didn't help", and a ground loop to the right occurred. According to tower personnel, the pilot was cleared to land on runway 8 but lined up and landed on runway 3. The recorded wind at the time of the occurrence was 090 at 14 knots. Based on the recorded wind and the runway used, the calculated head wind component was 7 knots and the calculated crosswind component was 12 knots. Casper Air Service and the Federal Aviation Administration conducted an examination of the aircraft and the owner contracted repairs with Casper Air Service and Airway Structural Repair, Eaton, Colorado, who was contracted to repair the left wing. Their damage assessment is copied in a letter to the owner/pilot and is attached. The repair station that conducted the damage assessment to the left wing noted that a Cessna 170A aileron was installed vice the proper aileron. According to information provided by the Cessna Aircraft Company, there are no known control deficiencies as a result of this type installation, but it was not approved, nor has it been tested, and the aircraft was not airworthy as a result.