On December 10, 2016, about 1130 central standard time, a Hiller OH-23B helicopter, N5776, impacted terrain during a practice autorotation near Tynan, Texas. The student pilot, who was the sole occupant, sustained serious injuries, and the helicopter was destroyed due to a post-impact fire. The helicopter was registered to Tynan Flyers, LLC, Tynan, Texas, and operated by a private individual as a 14 Code of Federal Regulations Part 91 instructional flight. Visual meteorological conditions prevailed at the time of the accident and a flight plan was not filed. The local flight departed a private residence about 1000. The student pilot reported he departed a private residence on his second solo flight. Prior to the accident, he completed two takeoffs and landings without incident. During a practice autorotation, the tail rotor struck the ground, the helicopter entered a spin, and came to rest near the place of initial impact. The student pilot reported there were no mechanical or system malfunctions with the helicopter prior to the accident. According to the student pilot's flight instructor who witnessed the accident, the student pilot appeared to be conducting a practice autorotation with a power recovery. The instructor reported the deceleration/flare was executed too low and the tail rotor struck the ground. The helicopter then spun 180 degrees and rolled over onto its left side. A small fire was noted near the engine and the student pilot was pulled from the helicopter by another witness. The helicopter was destroyed by a post-impact fire.