20030205001939A

(.19) On February 5, 2003, at 0815 mountain standard time, a cobb rotorway exec 90, N9876D, made a hard landing after experiencing a loss of tail rotor authority at the Phoenix Regional Airport (A39), casa grande, Arizona. Cobb international operated the helicopter as an instructional flight under the provisions of 14 CFR part 91. The helicopter was substantially damaged. The certified flight instructor (CFI) and the private pilot undergoing rotorcraft category training received minor injuries. Visual meteorological conditions prevailed for the local area instructional flight and no flight plan had been filed. The flight originated from stellar airpark (P19) about 0750, and was scheduled to terminate at P19. According to the CFI, the purpose of the flight was to practice pattern work and autorotations. The CFI stated that the student had done approximately four landing approaches. During the accident approach, the CFI reported that they had made the base turn and had leveled off when they heard a "bang." The CFI took the flight controls and initiated a turn to an open area for an emergency landing. During the autorotation, he raised the collective to check for aircraft controllability the helicopter yawed to the left, at which point he lowered the collective and decided to continue with the autorotation. As he pulled collective to "cushion the landing" the helicopter yawed to the left, landed firmly on the ground, and rolled over on to its right side. According to a federal aviation administration (FAA) inspector who examined the helicopter, the secondary drive shaft appeared to have sheared about midspan. The secondary drive shaft is being sent to the safety board for further examination. (-23) the student pilot was practicing a steep approach into A39 when a loud bang was heard from the rear of the helicopter. The instructor took control and realized there was no longer any control of the tail rotor. The instructor started a full auto-rotation descent of 65-70 mph. Prior to ground contact, the instructor started to flare and utilized full collective. At approx one foot off the ground, at full collective, the engine spooled up to approx 30% power due to the corrolator system. Without tail rotor control, the helicopter yawed to the left, the right skid made contact with the ground and rolled over onto its right side. Both occupants were able to exit th e helicopter through the front broken plexiglass. The helicopter received substantial damage and both occupants received minor injuries. No one on the ground was injured. --end--