History of Flight
On October 29, 2013, at 1720 Hawaiian standard time, a Eurocopter France AS350/B3 helicopter, registration N985EW, was substantially damaged during a hard landing at Kona International Airport in Kailua Kona, Hawaii. The flight instructor sustained minor injuries, while the commercial pilot receiving instruction was uninjured. The helicopter, operated by Air Medical Resource Group under 14 CFR Part 91, was conducting a local instructional flight that began about 1659. Visual meteorological conditions prevailed, and no flight plan was filed.
The intended first maneuver was practice of manual throttle control with the Full Authority Digital Engine Control (FADEC) governor disengaged. After startup, the helicopter repositioned to a taxiway with the governor engaged. The instructor then moved the governor switch to "MAN," disengaging the governor and illuminating the red "GOV" caution light. The commercial pilot found the twist grip throttle control excessively stiff. He checked the throttle friction wheel and confirmed no friction was applied. The instructor stated the stiffness was normal to prevent overcontrolling.
The commercial pilot lifted into a 3-foot hover and performed two 360-degree stationary turns using anti-torque pedals, maintaining NR within limits. The instructor then asked him to perform a left closed traffic pattern back to the departure point. The takeoff, transition to downwind, and initial descent were uneventful. On final approach to land south on taxiway A, below 400 feet, the commercial pilot noticed decreasing NR. He rotated the twist grip to increase power, but NR continued to drop. The low NR audio warning sounded, and the instructor joined him on the controls. Both pilots lowered the collective to enter autorotation. Despite the twist grip at maximum rotation, NR never recovered to normal.
At about 50 feet, the commercial pilot applied initial collective to reduce descent rate, but NR was too low. He adjusted cyclic to level the helicopter. Both pilots pulled collective to cushion the landing, but insufficient NR remained. The helicopter landed hard, slid forward on the taxiway, and yawed about 90 degrees left. After stopping, the commercial pilot did not shut down the engine or electrical power. The instructor stated the engine was not running; he applied the rotor brake and switched off the battery and engine switches before exiting.
Personnel Information
The flight instructor held a commercial pilot certificate with rotorcraft-helicopter and instrument-helicopter ratings, a flight instructor certificate with helicopter and instrument-helicopter ratings, and a second-class medical certificate dated January 3, 2013, with a limitation for near and intermediate vision. He had about 15,500 total flight hours, including about 15,000 in rotorcraft and about 1,500 in the accident make and model. He had given about 12,000 hours of flight instruction, with about 1,000 hours in that model.
The commercial pilot receiving instruction held a commercial pilot certificate with airplane single-engine land, multi-engine land, rotorcraft-helicopter, and instrument-helicopter ratings, and a flight instructor certificate with airplane single-engine land, helicopter, instrument-airplane, and instrument-helicopter ratings. He received a second-class medical certificate on October 1, 2013, with no limitations. Hired by Air Medical Resource Group on October 23, 2013, he had about 5,760 total flight hours, including about 5,484 in rotorcraft and about 6 in the accident make and model.
Aircraft Information
The helicopter, manufactured in 2000, had accrued about 2,634 hours at the time of the accident. It was powered by a Turbomeca Arriel 2B engine with a single-channel FADEC-type governor and a manual backup twist grip throttle control. The twist grip had two ranges separated by a disengageable "FLIGHT" stop, installed on the right side collective only. The AS350 B3 Flight Manual Supplement described procedures for FADEC-governor failure training, and the Flight Manual listed actions for a red "GOV" warning light, including maintaining NR in the green range and unlocking the FLIGHT detent. The limitations section specified NR ranges: with power on, ground low pitch 375-385 rpm, stabilized flight 385-394 rpm; with power off, 320-430 rpm. The low NR audio warning activated below 360 rpm.
Wreckage and Impact Information
Scars on taxiway A asphalt led from the initial impact point about 80 feet south to the helicopter's final position. Initial impact scars were consistent with skids and tail section contact. Skid scars ran parallel to the taxiway centerline before deviating left to the helicopter, which came to rest upright on an easterly heading. The tail boom separated from the fuselage, attached only by wires; the tail rotor guard was separated, the lower vertical fin bent right, and both tail rotor blades damaged. Main rotor blades showed no apparent damage.
Post-accident examination revealed the governor switch in the "AUTO" position; the instructor stated he moved it after the helicopter stopped. The twist grips were full open with the "FLIGHT" stop disengaged. Visual engine examination revealed no anomalies. The twist grip rotated freely through its full range, and the throttle friction control worked as expected. The Vehicle Engine Multifunction Display (VEMD) recorded a 21-minute flight (engine start to stop) with no over-limits or failures.
Tests and Research
The VEMD was examined at American Eurocopter in Grand Prairie, Texas, on December 12, 2013. The data confirmed no over-limits or failures during the accident flight or several preceding flights. The Digital Engine Control Unit (DECU) data download at Turbomeca USA matched the VEMD findings, with no faults recorded. The engine was examined and test-run at Turbomeca USA on the same day; it performed in both automatic and manual governor modes without anomalies or uncommanded shutdowns, meeting manufacturer's specifications.