HK 36 TTC tug engine power loss after takeoff; glider pilot released and outlanded

Shortly after aerotow takeoff from Schänis, the HK 36 TTC tug experienced engine power loss with strong vibrations. The Discus-2b pilot released; the tug pilot made an emergency landing ~1.5 km north of the airfield. Both pilots uninjured; no aircraft damage; slight field damage. The investigation was opened in Sep 2017 and closed in Aug 2022 with no operational, organizational, or systemic safety findings.

1. Aerotow initial climb: Discus-2b D-9830 on aerotow behind HK 36 TTC HB-2328 (both operated by Alpine Segelflugschule Schänis AG) shortly after takeoff from Schänis (LSZX) at ~14:27 LT.
2. Tug engine power loss + vibrations: The tug pilot felt the engine lose power and experienced strong vibrations.
3. Glider releases tow: The glider pilot released from the tow rope.
4. Tug emergency landing: The tug pilot carried out an emergency landing ~1.5 km north of Schänis airfield.
5. Glider outlanding; no damage: The glider landed safely off-field. Both aircraft were undamaged, with slight field damage and no injuries; no operational, organizational, or systemic safety issues were identified.