On April 25, 1998, about 1530 eastern daylight time, a Bell 206L-1, N60WJ, registered to Universal Air Service of Florida, Inc., was found to have damage from main rotor contact with the tail boom at Orlando Executive Airport, Orlando, Florida, following a Title 14 CFR Part 91 instructional flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The helicopter received substantial damage and the commercial-rated flight instructor and private-rated dual student were not injured. The flight originated from Orlando, Florida, the same day, about 1355. The instructor and dual student stated the flight was conducted as an instructional flight as part of a Bell Helicopter school. They departed Orlando Executive Airport about 1355, and stayed on the airport for the entire flight. During the first part of the flight, they performed touchdown autorotations. After completing the flight at about 1530, they were completing paperwork when maintenance personnel informed them about damage to the tailboom of the helicopter from a main rotor strike. They stated that at no time during the flight did they feel the main rotor contact the tailboom, and they did not feel any unusual vibrations during the flight.