On April 26, 1995, about 1912 eastern daylight time, a Pitts S-2B, N711BT, registered to Everglades Aerobatic, operating as a 14 CFR Part 91 instructional flight, ground looped on landing at Naples Municipal Airport and crashed. Visual meteorological conditions prevailed and no flight plan was filed. The airplane sustained substantial damage. The certified flight instructor/commercial pilot, and the rated student pilot (airline transport pilot) were not injured. The flight originated from Naples, Florida, about 50 minutes before the accident. the accident was initially reported to the NTSB as an incident, and was up-graded to an accident on May 10, 1995. The flight instructor stated he thought the rated student pilot allowed the airplane to roll too much to the right before exiting the runway. The student pilot applied left rudder, however, he thought the student pilot applied too much left rudder, and he applied right rudder. The airplane continued to the left 180 degrees. The right main landing gear collapsed, and the airplane came to a full stop. Examination of the airplane by the Director of Maintenance for Sun Aircraft Services USA, Inc., revealed the right spring on the tail wheel to be hanging free, the attachment clip was missing, and was not located. The flight instructor stated while taxiing to his hangar on a previous flight on April 12, 1995, the tail wheel steering did not feel right. Subsequent examination of the tail wheel assembly revealed the right spring was loose and the attachment clip had vibrated off. The airplane was taken to Naples Air Center, Inc., for repair. The tail wheel spring and attachment clips were worn and required replacement. Mr. Alfred A. Bennett, Naples Air Center, Inc., stated in a letter dated May 22, 1995, that it would be virtually impossible for a new attachment clip to vibrate loose from its installation and fall off during normal operation because of the tension required to open the clip. Possibly during a ground loop the stress in the opposing direction and the severe side load encountered may be enough to open or break the clip. Examination of photographs submitted with the NTSB Pilot/Operator Aircraft Accident Report of the tail wheel assembly revealed no evidence of distortion on the chain attached to the tail wheel spring.