NTSB Factual Report

On November 05, 2006, at 0924 Pacific standard time, a Eurocopter AS350B3, N109HP, experienced a hard landing while performing a practice hover autorotation at the Apple Valley Airport, Apple Valley, California. California Highway Patrol (CHP) Air Operations was operating the helicopter under the provisions of 14 CFR Part 91. The certificated flight instructor (CFI) and commercial pilot undergoing instruction were not injured; the helicopter sustained substantial damage. The local public-use instructional flight departed Apple Valley at 0806. Visual meteorological conditions prevailed, and a flight plan had not been filed.

In a written statement, the CFI reported that the purpose of the flight was to conduct training for the commercial pilot, who was positioned in right seat. After departure, the commercial pilot flew the helicopter to Southern California Logistics Airport, Victorville, California, where he performed about five straight-in practice autorotation maneuvers. The commercial pilot then flew the helicopter back to Apple Valley, performing a normal approach to a designated ramp area.

The CFI further reported that the commercial pilot configured the helicopter in a hover taxi to a concrete parking area, where the flight was to terminate. As the helicopter became aligned with the intended parking area it remained in a hover about 3 feet above ground level (agl). The CFI announced "hovering auto" and subsequently rolled the throttle to the idle position. In response, the commercial pilot abruptly lowered the collective to the down position and applied pressure to the left pedal. As soon as the CFI perceived that the commercial pilot had pushed the collective downward, he attempted to raise it. The helicopter stuck the ground hard in a level attitude and bounced back airborne while simultaneously yawing to the left. The helicopter reached about 5 feet agl and the CFI manipulated the collective to cushion the touchdown.

The CFI reported no mechanical malfunctions or failures with the helicopter prior to impact. The CFI stated that his total flight experience totaled 3,946 hours, of which 28 were accumulated while acting in the capacity of a flight instructor.

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 into the spring loaded override position." It further states that, "as the throttle is closed, apply proper antitorque pedal to maintain heading" and "leave the collective pitch where it is on entry." It then instructs that "at approximately 1 foot above the surface, apply upward collective pitch control, as necessary, 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."

According to the Eurocopter AS350B3 Flight Manual, Section 3.1 Emergency Procedures, the first instruction in an autorotation landing from hover is to "not reduce collective pitch."

NTSB Probable Cause

the pilot's improper use of the collective control during a practice hover autorotation, which resulted in a hard landing. A factor in the accident was the certificated flight instructor's inadequate supervision of the maneuver.