On February 29, 2012, about 1715 Pacific standard time, a Eurocopter AS 350-B3, N341HP, made a hard landing at the Napa County Airport, Napa, California. The helicopter was substantially damaged during landing. The commercial pilot held a certified flight instructor (CFI) certificate, and he was providing instruction to the second pilot, who held a commercial pilot certificate. Neither pilot was injured. The California Highway Patrol (CHP), Sacramento, California, owned and operated the public use helicopter. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed. No flight plan was filed for the local area instructional flight that originated from Napa about 1600. CHP management personnel reported that, at the time of the accident, the CFI was handling the flight controls. While hovering about 3 feet above ground level, the CFI performed an autorotation demonstration for the second pilot. Although the CFI raised the collective to arrest the descent prior to landing, the helicopter made a firm touchdown. The CFI reported no mechanical malfunctions or failures with the helicopter prior to impact. The CFI stated that his total flight experience totaled 2,783 hours, of which 409 were accumulated while acting in the capacity of a flight instructor. During a subsequent examination of the tail boom, numerous dimples in the skin were noted near the area where the tail boom attaches to the fuselage. The tail boom was removed from the helicopter and transported to Eurocopter's Texas facility for repair. The Federal Aviation Administration Rotorcraft Flying Handbook states that as part of the technique for practice autorotation maneuvers from altitude, the pilot should "smoothly, but firmly lower the collective pitch control to the full down position, maintaining rotor r.p.m. in the green arc with throttle." To practice hovering autorotations, it instructs the pilot to "firmly roll the throttle to the engine idle position" It further states that, "As the throttle is closed, apply proper antitorque pedal to maintain heading" and "Do not adjust the collective pitch on entry." It then instructs that "When the helicopter has settled to approximately 1 foot AGL, apply upward collective pitch control while holding the throttle in the idle detent position to slow the descent and cushion the landing," and notes that "usually the full amount of collective pitch is required." The manual lists one of the common errors of practice hovering autorotations to be the pilot's failure to "apply up-collective pitch properly, resulting in a hard touchdown."