Linden, NJ, USA
N906BA
EUROCOPTER AS-350-BA
The flight instructor was monitoring the student pilot during a 180-degree autorotation as part of the flight training. The maneuver was entered at 700 feet above the ground and at 100 knots. Once the intended spot was made for the 'power-on' recovery, the flare was started. As the flight instructor advanced the fuel flow control valve into the flight position, the helicopter started to settle and the low rotor speed horn came on. The flight instructor took over the controls advising the student pilot that it was going to be a run-on landing. During the landing, while in the ground run, the nose of the helicopter pitched forward as the skids dug into the mud. The flight instructor pulled back on the cyclic to prevent the blades from contacting the ground. The helicopter came to rest in the upright position in the grassy area. Post accident inspection of the helicopter’s main rotor system revealed that the 2,167 hours time in service Starflex component had two of its three arms fractured. Examinations of the fracture surfaces revealed no indications of any pre-existing damage to the areas. The fractures were consistent with overstress and unusual loads, which were produced during abrupt flight control inputs with low main rotor RPM.
On September 19, 2008, at 1745 eastern daylight time, a Eurocopter AS-350-BA, N906BA, incurred substantial damage during a run on landing at the Linden Airport (LDJ), Linden, New Jersey. The helicopter was operated by Liberty Helicopters. Visual meteorological conditions prevailed and no flight plan was filed for the Title 14 Code of Federal Regulations Part 91, instructional flight. The commercial certificated flight instructor and the commercial certificated student pilot were not injured. The flight instructor stated that the student pilot was performing a 180 degrees autorotation as part of the flight training. The maneuver was entered at 700 feet above the ground and at 100 knots. The 180 degrees turn to the predetermined spot was good. Once the spot was made for the power recovery, the flare was started. The flight instructor advanced the fuel flow control valve into the flight position, the helicopter started to settle and the low rotor speed horn came on. The flight instructor took over the controls and told the student pilot that it was going to be a run on landing. During the landing, while in the ground run, the nose of the helicopter pitched forward when the skids went into the mud. The flight instructor pulled back on the cyclic to prevent the blades from contacting the ground. The helicopter came to rest in the upright position in the grass area. They disembarked on their own after shutting down the helicopter. Post event inspection of the helicopter’s main rotor system revealed that the 2,167 hours time in service Starflex component had two of its three arms fractured. The Starflex was sent to the National Transportation Safety Board Materials Laboratory for a fracture surface examination. There were no indications of any pre-existing damage to the Starflex arms. The fractures were consistent with overstress and unusual loads, which are produced during abrupt flight control inputs with low main rotor RPM.
The flight instructor’s delayed remedial action (flight control inputs) during a practice autorotation/run-on landing resulting in fracture damage to the main rotor system Starflex.
Source: NTSB Aviation Accident Database
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