Incident Overview
On June 11, 2014, about 1140 Alaska daylight time, an Airbus (formerly Eurocopter) AS350 B3 helicopter, registration N356EV, sustained substantial damage during an engine start incident near Anchorage, Alaska. The helicopter was operating as a Title 14 Code of Federal Regulations Part 91 personal flight.
Pilot and Operational Details
The first pilot, a certificated flight instructor, reported that he had been hired to ferry the recently-purchased helicopter to Georgetown, Texas. He was providing transition training on the AS350 B3 to the second pilot, who was the new owner. After two unsuccessful attempts to start the helicopter, the first pilot requested assistance from a mechanic. The mechanic contacted the operator’s rotor wing training manager for guidance. While the first pilot was on the phone with the training manager discussing the correct starting procedure, the second pilot exited the helicopter, and a mechanic boarded and sat in the right seat. Once the helicopter was successfully started, the mechanic disembarked, and the second pilot re-boarded and took the right seat.
Sequence of Events
The first pilot noted that while the helicopter was operating at flight-idle, the yellow "TWT.GRIP" light illuminated on the annunciator panel. He instructed the second pilot to slowly advance the collective-mounted throttle twist grip to the open position until the light extinguished. As the second pilot began advancing the throttle, the engine speed immediately increased to a very high rpm, causing the helicopter to shake violently and subsequently rotate about 240° to the left. The first pilot performed an emergency engine shutdown, and both pilots exited the helicopter.
Damage and Systems Examination
The helicopter’s fuselage and main rotor drive system sustained substantial damage. The helicopter was equipped with a Turbomeca Arriel 2B-series turbine engine with a single-channel full authority digital engine control (FADEC) fuel control system.
A detailed wreckage and engine systems examination revealed no preaccident mechanical failures or malfunctions that would have precluded normal operation. The hydro-mechanical metering unit (HMU), digital engine control unit (DECU), and vehicle and engine multifunction display (VEMD) were removed and sent to Turbomeca USA’s analytical facility in Grand Prairie, Texas. The HMU operated in accordance with manufacturer’s specifications when tested. The VEMD and DECU downloads showed no discernable fault codes related to the accident start sequence, though the VEMD recorded a significant main rotor overspeed during the event.
Pilot Experience and Notices
The first pilot reported extensive experience in various Airbus/Eurocopter helicopter models, including about 6,000 flight hours in AS350 B2 helicopters and about 2,000 hours in AS350 B3 helicopters. However, he noted that his AS350 B3 experience was primarily with the Turbomeca Arriel 2B1-series engine (dual-channel FADEC) and could not recall how much experience he had with the 2B-series engine. He believed he followed the engine start procedures in the helicopter’s flight manual.
The operator’s rotor wing training manager stated, “I sensed when talking with the pilot that he did not have much experience, at least quality experience, with the AS 350 helicopter, especially the AS 350 B3…”
Airbus/Eurocopter Information Notice number 2169-I-67, dated June 6, 2010, specifically alerts operators to the different starting procedures for AS350 B3 helicopters equipped with 2B- and 2B1-series engines.