Aircraft Accident/Incident Report

St. Thomas, Virgin Islands 00801
Saturday, September 4, 2004 10:30 AST

The pilot stated that the helicopter was parked on a dock at the Crown Bay Marina in a northeasterly heading. After starting the engine, he performed a pedal turn to the right, and brought the helicopter to a 4 foot hover with all engine indications in the green. He commenced a southeasterly takeoff profile into the 10-15 knot wind while maintaining a steadily climb at 30 to 40 knots. When the flight was at approximately 20 foot, the helicopter yawed to the right "sharply." He stopped the climb and was able to correct back to the original heading with left anti-torque pedal input. When the helicopter attained the original heading, it started spinning to the right "uncontrollably." He then entered an autorotation into the water where he and the passenger evacuated the helicopter before it sank approximately 60 yards from the dock. The pilot stated he maintained a southerly heading from the point of hovering to the autorotation and he did not contact any object during the entire flight. Examination of the tail rotor conducted by a Federal Aviation Administration (FAA) inspector revealed that the tailrotor drive shaft was fractured approximately six inches aft of the tailrotor drive shaft damper assembly. NTSB review of pictures provided by FAA revealed both ends of the fracture surfaces of the tailrotor drive shaft exhibited evidence of torsional twisting. The tailrotor blades were found to be fractured approximately 8 inches from the center of rotation. The FAA Rotorcraft Flying Handbook (FAA-H-8083-21) states that unanticipated yaw, also referred to as loss of tail rotor effectiveness (LTE), may occur in all single-rotor helicopters at airspeeds less than 30 knots, and occurs to the right in helicopters with a counter-clockwise rotating main rotor (Robinson 22). It is the result of the tail rotor not providing adequate thrust to maintain directional control. The suggested recovery technique of a sudden unanticipated right yaw is to apply full left pedal while simultaneously moving cyclic control forward to increase speed. As recovery is effected, adjust controls for normal forward flight. Collective pitch reduction aids in arresting the yaw rate but may cause an excessive rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor revolution per minute (RPM). NTSB review of the Robinson R22 Beta Pilot's Operating Handbook revealed that the recommended takeoff profile, from a hover, is to maintain 5 feet until reaching 40 knots. This is where a steady climb may be commenced while accelerating to 60 knots.

The failure of the pilot-in-command to comply with performance data related to the recommended takeoff profile and his failure to perform remedial action following reduced tailrotor effectiveness, resulting in subsequent initiation of an autorotation and ditching.