Whittier, AK, USA
N319LF
Aerospatiale SA319B
The commercial certificated pilot reported he was attempting to land a wheel/ski equipped helicopter on a metal landing grid. He said the helicopter began to vibrate in ground resonance as soon as the landing gear touched the grid, and he immediately lifted the helicopter into a low hover. The vibrations increased, and he attempted to move the helicopter away from the landing grid. He indicated he was unable to control the helicopter due to the main rotor system's severe vibrations. The helicopter's main rotor blades subsequently struck a tower about 30 feet from the grid, resulting in the helicopter striking the ground and rolling inverted. The pilot said there were no preimpact mechanical problems with the helicopter. The helicopter sustained structural damage to the fuselage, tail boom, and all rotor blades.
On August 21, 2003, about 1230 Alaska daylight time, a wheel/ski equipped Aerospatiale SA319B helicopter, N319LF, sustained substantial damage when it collided with an object and terrain following a loss of control while attempting to hover in ground effect. The accident occurred on Naked Island, about 40 miles east-southeast of Whittier, Alaska. The solo commercial pilot was not injured. The Title 14, CFR Part 91 positioning flight was operated by Last Frontier Air Ventures, Ltd; Palmer, Alaska. The flight operated in visual meteorological conditions, and company VFR flight following procedures were in effect. The flight departed Palmer, Alaska, about 1000, and the destination was Naked Island. The National Transportation Safety Board (NTSB) investigator-in-charge (IIC) had a telephone conversation with the pilot on August 21 at 1800. The pilot related he was positioning the helicopter to board a passenger he had left at a radio tower site earlier that day. He said there was a small steel grid that was used as a helipad located about 30 feet from the radio tower. As he attempted to land on the grid, the helicopter began to vibrate significantly in ground resonance as soon as he placed the wheel/skid landing gear on the grid. He indicated he aborted the landing attempt, and brought the helicopter to a low hover until the vibration stopped. He said he made one more attempt to land on the grid, but the helicopter started to vibrate much more violently as he placed the landing gear on the grid. He brought the helicopter to a low hover again, but said the vibration associated with the helicopter's main rotor system increased instead of dissipating. He said he tried to fly the helicopter away from the pad and tower, but the cyclic control was unmanageable, making uncommanded movements from stop to stop. The helicopter's main rotor blades subsequently struck the radio tower, and the helicopter collided with terrain and rolled inverted. The pilot said the engine was still running after the impact, and he shut the engine off and was able to exit the wreckage without assistance or injury. He indicated he was unaware of any preimpact mechanical problems with the helicopter, and that the weather at the crash site was excellent, with no wind. The helicopter sustained structural damage to the fuselage, tail boom, and all rotor blades.
The pilot's encounter with ground resonance during landing, which resulted in an aborted landing and subsequent loss of control of the helicopter.
Source: NTSB Aviation Accident Database
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