On September 29, 2018, at approximately 12:40 EDT, a Diamond DA20-C1, registration N397JA, and a Piper PA28R-180 collided at Sebring Regional Airport (SEF) in Florida. The Diamond aircraft was being used for instructional flight operations, while the Piper was operating a personal flight. The collision resulted in one minor injury to a student pilot; the flight instructor in the Diamond and the pilot and passenger in the Piper were not injured. Both aircraft sustained substantial damage.
At the time of the accident, the weather was characterized by visual meteorological conditions with winds from 100 degrees at 5 knots. The Diamond aircraft was performing touch-and-go landings on runway 14. The flight instructor reported seeing the Piper arriving from the west while on the upwind leg of the traffic pattern. However, after the student pilot turned onto the crosswind and download legs, the instructor lost sight of the Piper. The instructor noted that the student pilot announced their position on every leg of the pattern, but there was no audible acknowledgment from the Piper.
The Piper pilot reported approaching the airport from the northwest and turning onto the downwind leg for runway 19. The pilot stated that while flaring approximately one to two feet above runway 19, a flash was observed off the right wing, immediately preceding the collision. The collision occurred as the student pilot in the Diamond advanced the throttle to full power for a takeoff attempt, at which point the Piper's left wing contacted the tail of the Diamond.
The investigation
Post-accident examination of the Diamond aircraft's transceiver showed it was set to the published CTAF frequency of 122.7 MHz. The Piper's transceiver, however, was set to 122.725 MHz. Testing confirmed that while transmissions from the Diamond were audible on a portable VHF transceiver, transmissions from the Piper on its as-found frequency could not be heard. When the Piper's transceiver was switched to the correct published CTAF frequency, communications were clear.
An analysis of recorded LiveATC.net audio from the period showed that radio calls from the Diamond were heard for every leg of the traffic pattern. In contrast, only two radio calls attributed to the Piper were recorded, both of which were garbled and difficult to understand.