Accident Summary
A midair collision occurred between an aerobatic glider and a Piper J3C airplane at an uncontrolled airport. The glider, piloted by a commercial pilot with one passenger, was conducting aerobatic maneuvers within a designated aerobatic box adjacent to runway 5L. The Piper J3C, with two occupants—a commercial pilot/flight instructor/airplane owner in the front seat and a private pilot in the rear seat—had just departed runway 5L.
Sequence of Events
The aerobatic box measured 1 kilometer square and extended from the surface to 6,600 feet MSL (5,000 feet AGL). Its southern boundary was located approximately 1,490 feet north of the runway 5L centerline. Witnesses observed the glider completing a loop; as it reached the top, the nose lowered until the glider was pointing straight down. As the glider began to recover at about 600 feet AGL, the left wing of the oncoming Piper struck the glider's tail between the empennage and main fuselage, severing the empennage. The collision also caused a large portion of the Piper's left outboard wing to separate. Both aircraft then entered uncontrolled descents and came to rest near the center of the aerobatic box.
Airport Procedures and Communications
According to the airport facilities directory, aircraft departing from runway 5L are instructed to fly a right-hand traffic pattern. However, the airport's segmented circle depicts a left-hand departure from runway 5L. Radio-equipped aircraft may use a common traffic advisory frequency of 122.9 MHz. Neither the glider nor the Piper was equipped with a radio, nor were they required to have one. The front-seat pilot of the Piper had based the accident airplane at the airport for several years and was familiar with local operating procedures.