ASW 24 E stalls in downwind after engine trouble on self-launch

After a self-launch from Bremgarten, the pilot of an experimental ASW 24 E was fatally injured and the glider destroyed by post-impact fire. Witnesses heard the engine running roughly from the takeoff roll. The glider gained only marginal height entering right downwind for RWY 05, where it was pulled into a steep nose-up attitude, stalled, dropped nose-down and impacted the grounds of a biogas plant south of the airfield. The glider was a Spanish-registered Experimental rebuilt with a non-aviation Aixro Wankel engine and held no valid airworthiness certificate.

1. Self-launch takeoff: At 12:03 LT the ASW 24 E self-launched from Bremgarten (EDTG) RWY 05 (asphalt) on a private VFR flight. Pilot held LAPL(S) with >2,000 h total on gliders/motor gliders; engine extended for the launch.
2. Experimental, no airworthiness cert: The glider was Spanish-registered as Experimental, rebuilt by the pilot from a wreck. ~2 years before the crash the original engine was removed and replaced with a non-aviation Aixro XF40 Wankel on a custom motor mount; ~3 weeks before the crash a second fuel tank was added. Modifications were made without consulting Schleicher. Aircraft held neither a preliminary nor a final airworthiness certificate, and operated in Germany without an entry permit.
3. Engine runs roughly from takeoff roll: From the start of the takeoff roll, witnesses heard the engine running roughly and stuttering.
4. Only marginal climb performance: The airfield manager observed only marginal height gain on departure as the glider turned into right downwind for RWY 05.
5. Steep pull-up in downwind: Another aircraft's crew and witnesses on the ground observed the glider being pulled into a steep nose-up attitude in the right downwind.
6. Stall and nose drop: Following the pull-up the glider abruptly dropped away (kippte ab) and descended with a steep nose-down attitude toward the ground.
7. Crash - fatal: The aircraft impacted the grounds of a biogas plant ~1.3 km south of Bremgarten, on the south-eastern edge of the Eschbach industrial area. The wreckage burned and ignited stored material at the facility. Engine was found extended. Pilot fatally injured; aircraft destroyed. Autopsy showed no acute medical event; cardiac cause could not be assessed due to severe injuries.