MURRELLS INLET, SC, USA
N6247A
Boeing HU-369-OH6A
The helicopter was in a 4-to 6-foot hover above the marsh's surface, maneuvering for film shooting. The pilot stated the helicopter began to spin clockwise despite his applying full left anti-torque pedal. Increasing collective did not remedy the uncommanded yawing, so he lowered collective and power, and settled into the marsh, collapsing the left skid and the three occupied seats. The tail boom was severed by a main rotor blade strike. Winds were from the south to southwest at 15 knots. Examination of the wreckage revealed no evidence of precrash failure or malfunction of the helicopter's flight controls, structure, or rotor drive system.
On June 25, 1999, about 1835 eastern daylight time, a Boeing 369-OH6A, N6247A, registered to Scott's Helicopter Services, Inc., operating as a Title 14 CFR Part 91 television news filming flight, crashed into a coastal marsh near Murrells Inlet, South Carolina. Visual meteorological conditions prevailed and no flight plan was filed. The aircraft sustained substantial damage and the commercially-rated pilot, a commercial pilot-rated passenger, and a passenger/photographer suffered minor injuries. The flight originated from Myrtle Beach, South Carolina, about 45 minutes before the accident. According to the pilot, as told to the NTSB via telephone just after the occurrence, he was in a hover about 4 to 6 feet above the water's surface, maneuvering the helicopter for film shooting when the tail rotor seemed to lose effectiveness. The helicopter continued to revolve in a clockwise direction despite applying full left anti-torque pedal. The pilot further stated he thought he had tail rotor drive problems and when he lowered the collective and reduced power to stop the rotating, the helicopter settled in the marsh. The left rear door had been removed. The pilot reported the winds at the accident site to be 200 degrees at 15 knots. The Myrtle Beach winds for 1845 were reported as 180 degrees at 15 knots. Sixteen statements from nine eyewitnesses, the left seat passenger, and a county sheriff who responded to the emergency call were submitted to the NTSB by a law firm and a private investigator retained by the pilot. The collective information stated that the helicopter was in a hover over the marsh, heading between south and west, at an altitude from 4 feet to 50 feet. When the helicopter transitioned from the hover to forward flight, it commenced a simultaneous climb and right turn, and after about 90 degrees of turn, the helicopter appeared to fly out of control. At that point, the craft abruptly pitched nose down and seemed to recover, and entered anywhere from 1 to 5 revolutions about the yaw axis before the pilot appeared to ease power and settle in the water, left skid first. Some witnesses stated they heard a different "whine" from the rotors at the point that control appeared to be lost. Three witnesses, including the pilot, think something flew off the helicopter before water impact. Five witnesses said they saw nothing fly off the helicopter, precrash. The sheriff's statement said some witnesses said something flew off as a result of water impact. A piece of one tail rotor blade that had sustained a chordwise fracture about 4 inches from its hub was found about 5:30 o'clock from the wreckage, 100 to 120 feet, and recovered by a police diver. The wreckage was recovered and transported to Georgetown County Airport, South Carolina, for FAA and factory inspectors examination. The collision with the swamp collapsed the left skid, shattered the cockpit glass, crushed the bottom of the fuselage, and distorted the door frames and the occupied seat supports. No precrash mechanical failures or malfunctions were detected. Airframe, main and tail rotor, and rotor drive damage appeared to be only impact related. All flight control and engine control path continuities were free, intact, and functional, except for some tail rotor control binding due to impact damage. Damage to the copilot's cyclic and anti torque pedals was noted and determined to be impact related. The tail boom and tail rotor drive shaft had been severed by a main rotor blade strike, post crash. The tail rotor gear box was intact and rotated freely. The tail rotor blade, (S/N 6088U) and its pitch control arm revealed only postcrash damage. The piece of tail rotor, (S/N 6089U) found remotely, and its mate were sent to the Boeing Helicopters, Mesa, engineering laboratory for failure analysis. By macroscopic examination, the pitch control arm was determined to have been fractured by a bending, unidirectional overstress due to impact. The Boeing Helicopters engineering laboratory report is included under, "Reports from Parties to the Investigation". Weight and balance and power/torque available vs power/torque required computations were made using the known loading of the helicopter and two separate fuel quantities: (1) 10 lbs. less than full fuel and, (2) full fuel less one hour of fuel burn. Using conditions reported at the accident site, the weight was within limits, the center of gravity was within limits, and the power/torque available exceeded what was required.
An inflight loss of control due to loss of tail rotor effectiveness as a result of the pilot's inadequate compensation for the winds and improper weather evaluation.
Source: NTSB Aviation Accident Database
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