Accident Overview
On September 24, 2020, about 1918 central daylight time, a Cessna 172, N108VK, and a Team Rockets F1, N540LK, were involved in a mid-air collision near San Marcos, Texas. The Cessna sustained substantial damage, and the F1 was destroyed. The flight instructor on the Cessna received minor injuries, the student pilot was seriously injured, and the F1 pilot received minor injuries.
Flight Operations
The Cessna was operating under Title 14 Code of Federal Regulations Part 91 as an instructional flight, while the F1 was operating under Part 91 as a personal flight. San Marcos Regional Airport (HYI) had an air traffic control tower that was closed at the time. Aircraft self-reported on the common traffic advisory frequency (CTAF). A recording of radio communications and a GoPro video from the Cessna's cockpit were obtained.
Sequence of Events
The Cessna entered the left downwind for runway 8 at about 1912 for a full-stop landing, with the student pilot flying. There were six other aircraft in the traffic pattern or communicating on CTAF, including the F1. The F1 pilot entered the left downwind from the northeast, noticed an airplane ahead, performed a 360° right turn for spacing, and reentered downwind. The instructor on the Cessna heard the F1 but did not see the 360° turn and tried to locate it using ADS-B.
As the F1 approached the runway 8 threshold, the Cessna queried if the turning airplane had rejoined. The F1 pilot responded affirmatively and was about to turn left base but saw a Cessna below him at 2 o'clock, 0.7 to 0.9 miles away. The instructor took control, announced a left base turn over the stadium (Texas State University football stadium, 2.9 miles east of runway 8), and started the turn.
At 19:15:40, the F1 pilot announced he would extend downwind and rejoin on final. Another aircraft announced short final. At 19:16:24, the F1 pilot reported inbound over Interstate 35 (I35), about 2.25 miles east of the runway. He stated he visually cleared his flight path and saw no other aircraft until the collision.
At 19:17:20, the F1 pilot reported 1-mile final. The instructor looked outside, and at 19:17:25 the Cessna radioed 0.8 mile on final. No further radio calls were made. The instructor focused on the runway after 19:17:52, when the Cessna's altitude was 750 ft mean sea level (155 ft above ground).
Collision and Aftermath
The F1 pilot felt and saw the other aircraft impact from the right, 5 o'clock position shortly after his 1-mile call. The instructor felt the F1 impact from above and left; the F1's propeller hit the Cessna's windshield and cowling. The instructor lost control, and the Cessna hit the ground, inverted, on the airport perimeter road. The F1 stopped against the perimeter fence. The F1 pilot exited and assisted the Cessna's occupants. The F1 later caught fire and was destroyed. The Cessna sustained substantial damage to the fuselage, empennage, and both wings.
Additional Information
The F1 was a low-wing monoplane not equipped with ADS-B; the Cessna was a high-wing monoplane with ADS-B. The FAA Airplane Flying Handbook notes that traffic pattern entry should be at a 45° angle to the downwind, and that banking can uncover blind spots. Mid-air collisions are most likely between aircraft going the same direction.