Piper Archer collides with ASW 15 in busy uncontrolled circuit

Three people were killed and one seriously injured when a Piper PA-28 and an ASW 15 collided near Yverdon, an uncontrolled airfield with intense mixed traffic; both aircraft destroyed. The Piper, returning from Blécherette with four onboard, turned left between the runway and the powered downwind onto a path leading directly to a glider in the runway-23 loss-of-altitude area. The Piper pilot did not see the glider and struck its tail from behind at ~250 m AGL. The glider fell inverted; the Piper spun into nearby trees.

1. Return to Yverdon — approach: After an aerotow departure from Yverdon and a soaring flight of ~3 hours, the ASW 15 glider HB-1013 returned to Yverdon and entered the loss-of-altitude area for RWY 23.
2. Intense local traffic: At the time of the approaches there was intense mixed traffic at Yverdon — powered aircraft, gliders, and parachuting activity — increasing pilot workload and potential for distraction.
3. Mixed circuit operations: The glider HB-1013 and aerobatic aircraft HB-SAN coordinated their landing sequence on the common frequency while the Piper HB-PKL also approached and maneuvered in the same circuit area.
4. Piper turns toward glider: While HB-1013 was in the glider loss-of-altitude area, the Piper HB-PKL turned left after reporting overhead the field, on a path leading directly toward the glider.
5. No effective avoidance: There is no indication from witnesses or radio calls that either the glider pilot or the Piper pilot saw the conflict in time to take effective avoiding action before impact.
6. Mid-air collision: HB-PKL collided with HB-1013 from behind, striking first the glider's tailplane and then its fuselage, fatally disrupting the glider's flight.
7. Crash - fatal: The glider fell inverted into a field; the Piper entered a spin and crashed into trees. Both aircraft were destroyed; the glider pilot and two Piper passengers were killed.