G 103 hits runway hard after winch cable auto-releases at 30 m

Both occupants of a Grob G 103 C Twin III ACRO were seriously injured during a winch launch from RWY 03 at Erbach and the aircraft was substantially damaged. The instructor held 385 hours total with 257 on type. Shortly after liftoff the cable tension dropped sharply, the rope went slack and the cable auto-released from the launch hook at about 30 m AGL. The instructor reduced the climb angle, but the glider touched down hard on the winch strip 245-270 m from the start point, breaking the fuselage tube about 15 cm ahead of the tail. The investigation attributed the sequence to the cable releasing while still in the initial climb.

1. Winch launch RWY 03 ~12:15 LT: At about 12:15 LT on 16 June 2014 an instructor and student began a winch launch in a Grob G 103 C 'Twin III ACRO' from RWY 03 at Sonderlandeplatz Erbach (EDNE), a 760×20 m glider strip at 1,558 ft AMSL. Wind was 040° at 7-10 kt; CAVOK. The instructor held a glider FI rating with 385 hours total, 257 hours over 528 flights on this type, and 17 flights in the last 90 days.
2. Cable tension drops, slack develops: Shortly after liftoff witnesses saw the winch cable tension drop sharply. Significant slack developed along the cable.
3. Instructor reduces climb angle: The instructor noticed the drop in cable tension and reduced the glider's climb angle in response.
4. Auto-release at ~30 m AGL: With strong slack on the cable the launch hook released automatically at about 30 m above the ground, ending the launch.
5. Hard touchdown 245-270 m from start: Following the aborted launch the glider settled and contacted the winch strip hard. The first tail-wheel mark was 245 m from the start point and the aircraft came to rest about 270 m from the start.
6. Fuselage breaks ahead of tail: The fuselage tube broke about 15 cm ahead of the tail; the rudder and horizontal stabiliser were also damaged. There was no fire. Both occupants were seriously injured.