The glider pilot reported that, during an aerotow takeoff and after becoming distracted by something in the cockpit, he looked back outside and noticed that he was about 100 ft higher than the tow airplane. He added that he attempted to correct, "but the tow hook released on its own." The pilot turned the glider to the left, the left wing impacted the ground, and the glider came to rest in some brush. The glider sustained substantial damage to the fuselage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the glider that would have precluded normal operation. The Federal Aviation Administration's Glider Flying Handbook, FAA-H-8083-13A, "Normal Assisted Takeoff" section, stated, in part: One of the most dangerous occurrences during aerotow is allowing the glider to fly high above and losing sight of the towplane. The tension on the towline caused by the glider pulls the towplane tail up, lowering its nose. If the glider continues to rise, pulling the towplane tail higher, the tow pilot may not be able to raise the nose. Ultimately, the tow pilot may run out of up elevator authority.