Accident Overview
On September 19, 2008, at 1745 eastern daylight time, a Eurocopter AS-350-BA (registration N906BA) operating as a Part 91 instructional flight incurred substantial damage during a run-on landing at Linden Airport (LDJ) in Linden, New Jersey. The helicopter was operated by Liberty Helicopters. Visual meteorological conditions prevailed and no flight plan was filed. The commercial certificated flight instructor and commercial certificated student pilot were not injured.
Flight Sequence
The flight instructor reported that the student pilot was practicing a 180-degree autorotation. The maneuver was initiated at 700 feet above ground level and 100 knots. The 180-degree turn to the predetermined spot was performed satisfactorily. After the spot was reached for the power recovery, the flare was initiated. The flight instructor then advanced the fuel flow control valve to the flight position. The helicopter began to settle, and the low rotor speed horn activated. The instructor took control and informed the student that a run-on landing would be performed.
Landing and Damage
During the landing ground run, the helicopter's skids entered mud, causing the nose to pitch forward. The flight instructor pulled back on the cyclic to prevent the main rotor blades from contacting the ground. The helicopter came to rest upright on the grass. Both occupants disembarked without assistance after shutting down the helicopter.
Post-Event Inspection
Examination of the main rotor system revealed that the Starflex component, which had 2,167 hours in service, had two of its three arms fractured. The Starflex was sent to the National Transportation Safety Board Materials Laboratory for fracture surface analysis. No pre-existing damage was found on the Starflex arms. The fractures were consistent with overstress and unusual loads generated during abrupt flight control inputs when main rotor RPM was low.