On June 20, 2002, about 1620 eastern standard time, a Cessna 208B, N786DM, registered to and operated by Isla Nena Air Service Inc., had a midair collision with a Britten-Norman BN-2B-26, N663VL, registered to and operated by Vieques Air Link Inc., while on final approach to runway 9, at the Antonio Rivera Rodriguez Airport (VQS), Isla De Vieques, Puerto Rico. Visual meteorological conditions prevailed at the time and company VFR flight plans were filed for the 14 CFR Part 135 on-demand air taxi flights. Both airplanes were substantially damaged. The commercial-rated pilots from both airplanes reported no injuries. Nine passengers on board N786DM, and five passengers onboard N663VL, reported no injuries. Both airplanes landed without further damage. The Cessna had departed from Culebra, Puerto Rico, at 1610. The Britten-Norman had departed from Fajardo, Puerto Rico, at 1600. According to both pilots, they had reported their positions on the UNICOM frequency, and announced their intentions. The Cessna pilot said that he entered traffic on the downwind at 1,000 feet, on a 45 degree angle, and turned base to final. He said he made radio calls announcing his intentions on UNICOM, 12 miles northeast of the airport, and at 9 miles northeast of the airport. He heard "no reply," entered downwind at 1,000 feet, then turned base leg to final. After turning final he said he "still heard no reply," on the radio, and at about 500 feet he "felt a bump." He then called out on the radio, "…what [the] hell is going on," and initiated a go around. According to the pilot of N786DM it was after the collision when "…the other aircraft established communication. He called out short final. I looked down and saw the other aircraft. He replied talking to the helicopter." The pilot of N786DM said he called go-around to land runway 9, upwind to crosswind leg, and then the helicopter reported to him that his "wingtip was missing." He had one of his passengers verify that the landing gear were all right and landed on runway 9 without further incident. The Britten-Norman (N663VL) pilot said he turned left from base leg to final approach, but did not mention anything about a downwind leg. He said he contacted VQS UNICOM on 123.00 about 9 miles northwest of the airport. According to the pilot of N663VL "…nobody on the frequency responded except for [a] helicopter transitioning to Vieques." The helicopter pilot told him that he was at 500 feet heading to a resort landing site next to VQS airport. The pilot of N663VL told the helicopter pilot he had him in site, and reported his altitude as 1,000 feet. The pilot of N663VL said he was "3 miles northwest" when he transmitted his intentions again, and said that at that time "nobody answered at the UNICOM, and...I entered on left base." He did a third radio call and "nobody responded." He then turned onto final leg, he transmitted again, no one answered, and a "few" seconds after that a voice at the UNICOM in Spanish said "...traffic on final," and he replied "Vieques 663 final for runway 9 Vieques." Within 5 to 10 second the pilot of N663VL said he "felt the impact on my left wing...[and he] saw a Cessna Caravan (N786DM) on my left side." He said he "lost" control of the aircraft for a few seconds, regained control and landed without further incident. Both airplanes touched wing tips; the Cessna's damage was to the right wing and the Britten-Norman's damage was to the left wing. The reported weather at San Juan (SJU), Puerto Rico, 34 miles northwest of the crash site, at 1656 was; 2,700 few, visibility 10 sm, winds 070 at 14 knots with gusts to 19 knots, temperature 84 degrees F, dew point 73 degrees F, and the altimeter was 30.01 inches Hg.