L-13 Blaník breaks a wing landing hard out of a sideslip on final

An L-13 Blaník on a training circuit at Frýdlant landed hard and sideways after a probably late sideslip recovery; instructor and student were unhurt, but the glider was substantially damaged. The instructor took over on base; with flaps and full airbrakes out on final the glider still did not sink markedly, so at about 30–40 m he began a short sideslip, and the sink rate rose sharply. The speed was probably not held in the slip: coming out of it, the controls felt soft and sluggish, so he pushed and waited for speed, and closed the airbrakes just before touchdown.

1. Dual winch circuit: The instructor and an ab-initio student were winch-launched from Frýdlant at 08:32 on the student's first winch launch. After release at about 150 m AGL the student flew a small right-hand circuit.
2. Instructor takes over on base: Between the third and fourth turns the student extended the flaps and the instructor took the controls. The airspeed indicator read 80 km/h, but the glider felt slow over the ground to him.
3. Little sink with full airbrakes: After the turn to final he extended the airbrakes fully. Several seconds later the glider was still not sinking markedly; at a glance the variometer showed 2–3 m/s down.
4. Short sideslip at 30–40 m AGL: At about 30–40 m AGL he began a short sideslip to steepen the descent, and the sink rate rose markedly. The training manual requires a slip to be recovered by 25 m AGL.
5. Waits for speed, closes airbrakes: Coming out of the slip he found the controls soft and responding little. He pushed and waited for speed, and just before touchdown, drifting markedly sideways, closed the airbrakes sharply.
6. Sideways touchdown, wing broken: At 08:36 the glider touched down at a high sink rate, drifting sideways, about 110 m past the threshold; the wheel hit sideways and the glider stopped after 35 m. The left main spar flange broke.