On May 30, 1999, at 0854 hours mountain standard time, a Cessna 172P, N66018, collided in flight with a HOAC-Austria HK 36R Super Dimona, N1066F, while both aircraft were on landing approach at Falcon Field, Mesa, Arizona. Both pilots were able to land their aircraft. The Cessna was operated by Southwest Flight Center as a dual instructional flight under 14 CFR Part 91 and was substantially damaged. The Cessna departed from Scottsdale, Arizona about 0800. The HOAC-Austria was operated by Sky King Soaring as a personal flight under 14 CFR Part 91 and received minor damage. The HOAC-Austria departed from Falcon Field about 0850. There were no injuries sustained by the commercial certificated flight instructor or student pilot in the Cessna nor by the commercial certificated pilot and passenger in the HOAC-Austria. Visual meteorological conditions prevailed and neither aircraft was operating on a flight plan. The pilot of the Cessna reported that he and his student departed Scottsdale airport and went to Falcon Field to practice touch-and-go landings. They had completed three touch-and-goes in left traffic to runway 4L and were on downwind for the fourth touch-and-go at the time of the collision. They were on downwind leg, in level flight, and the student had reduced power to 2,300 rpm. They were flying about 100 knots IAS. He recalled asking his student if he had his traffic in sight and the student identified traffic well in front of them. About that time he heard a "motorglider" call the tower on downwind. Since that was approximately their position, he looked to the right anticipating traffic turning downwind from the 45. While he was looking to the right he felt the collision. He doesn't recall that the tower ever issued them a landing sequence or pointed out the traffic they collided with. He said the tower was "not too busy," and there were at least four aircraft in the airport traffic pattern. In a later correspondence, the pilot reduced his estimate of airspeed to 85 knots IAS. The pilot of the HOAC-Austria reported that they had just departed on runway 4R and intended to remain in the pattern to practice touch-and-go landings. At Falcon Field, he said, all traffic is left-hand to the north of the airport for runways 4L and 4R due to a noise sensitive area south of the airport. He said that the tower told him to expect to follow a Cessna taking off on runway 4L and to continue upwind and the tower would call his crosswind leg. His upwind was longer than normal. He recalled seeing another Cessna, which entered downwind from the 45, and recalled following that aircraft but doesn't recall ever seeing a Cessna departing off 4L or the tower directing his attention to that aircraft after takeoff. About 15 seconds after reporting downwind to the tower, and while in level flight on downwind leg opposite the tower, the midair collision occurred. He felt a jarring, heard a lot of noise, and then saw a Cessna in front of his plane going away from him. He reported his aircraft's speed on downwind was 75 knots. He said there was damage on his airplane on the lower surface of the right wing about 3 feet outboard of the fuselage that angled toward the nose of his aircraft. There was also paint transfer from the Cessna on the right side of his aircraft's engine cowl and damage to the propeller and spinner. According to an inspector from the Federal Aviation Administration (FAA) Scottsdale Flight Standards District Office, the upper 2/3 of the vertical fin and rudder of the Cessna were damaged and the fuselage tailcone was buckled forward of the horizontal stabilizer. According to the same inspector, the impact mark on the underside of the right wing of the HOAC-Austria started at mid-chord, about 3 feet outboard of the fuselage, and angled inboard approximately 45 degrees toward the nose. COMMUNICATIONS An Air Traffic Control Group was formed and the group chairman's factual report is attached. According to that report, initial radio communications were established between N66018 and the local controller at 0836:20 when the pilot of that aircraft advised, " . . . over fountain hills for touch and goes with zulu." The local controller replied, "six six zero one eight falcon tower ident ah left traffic runway four left." The pilot acknowledged the instruction. At 0839:35, the tower advised, "cessna zero one eight runway four left cleared touch and go left closed traffic approved." The pilot acknowledged the clearance. At 0844:31, the local controller transmitted, "cessna zero one eight number two follow cessna on a short final runway four left cleared touch and go." At 0844:37, the pilot replied, "(unintelligible) the cessna zero one eight second after the Cessna." At 0849:07, the local controller transmitted, "cessna zero one eight you're number two follow cessna left base runway four left cleared touch and go traffic off your right is landing ahead and to your right is landing runway four right." The pilot replied, "see both traffic cessna zero one eight." At 0849:23, the pilot of N1066F established initial radio contact with the local controller advising, "falcon tower motorglider one zero six six foxtrot with you at runway four right ready for takeoff." The local controller replied, "motorglider six six foxtrot falcon tower runway four right cleared for takeoff say direction." The pilot responded, "closed traffic six six fox." At 0849:38, the local controller advised, "motorglider six six foxtrot left closed traffic approved I'll call the crosswind." The pilot acknowledged. At 0851:03, the local controller transmitted, "motorglider six six foxtrot you'll be following the cessna ahead and to your left." There was an unintelligible response. At 0851:15, the local controller transmitted, "six six foxtrot did you copy." The pilot replied, "six six fox we're following the Cessna." At 0851:54, the local controller transmitted, "and motorglider six six foxtrot additional traffic ah ahead and to your left a cessna entering downwind can you follow him." At 0852:00, the pilot replied, six six foxtrot has the traffic in sight." At 0853:24, the local controller transmitted, "cessna zero one eight verify you're left downwind abeam the numbers." There was no response. At 0854:25, the controller transmitted, "motorglider six six" and at 0854:32, motorglider N1066F transmitted, "emergency emergency ah november one zero six six foxtrot midair collision there's a cessna going down." At 0854:39, the controller transmitted "ok cessna going down you're cleared to land any runway cessna on short final six six niner go around go around start a climb now immediate," and at 0854:50, the controller transmitted "six six foxtrot you're cleared to land any runway and the cessna on left base say your numbers." In his interview, the local controller said that traffic was starting to get busy. He believed there were six aircraft in the traffic pattern and five more awaiting takeoff at the time of the accident. Cessna N66018 was supposed to follow motorglider N1066F, however, the controller had not given the Cessna his traffic sequence because he had not had a chance to do so. The controller acknowledged that he had become confused with the landing sequence, and, at the time of the collision, he was looking at another Cessna aircraft, which was turning from base leg to final approach. The controller also acknowledged that he had not seen Cessna N66018 or motorglider N1066F turn from upwind to crosswind and, in his mind, the motorglider was well ahead of the Cessna. The tower supervisor, in his interview, noted that there were no visitors and no extraneous conversations going on in the tower. At the time of the accident his attention was focused on the approach end of the runway. He observed the two accident aircraft about 1 second prior to impact, at the same time the local controller did, and there was nothing he (the supervisor) could do. In his written statement, the supervisor reported "I observed a Cessna climbing on the downwind into an aircraft above him." The ground controller, the only other person in the tower, said in his interview that he too had seen the two aircraft on downwind immediately prior to the collision but with insufficient time to relay an alert to the local controller. In his written statement, the ground controller reported, "I observed C172, N66018 passing underneath Katana N1066F. N66018 appeared to climb into N1066F, resulting in the collision of the two aircraft." The Safety Board Group Chairman noted that recorded radar data provided by Phoenix terminal radar approach control (TRACON) was deemed unusable because of target overlap, congestion near the runway environment, and the fact that all aircraft had been assigned a radar beacon code of 1200.