Accident Overview
On a training mission over Douglas Island, approximately two nautical miles west of Pitt Meadows Airport, British Columbia, a Eurocopter AS 350-B3 (registration N530NA, serial number 3209) sustained a hard landing. The aircraft was being used for longline operation demonstration. At about 1100 Pacific standard time, the helicopter, hovering with a 100-foot longline near a 30-foot tree, descended about 10 feet. The pilot-in-command (training pilot), seated in the left seat, attempted to arrest the descent by raising the collective, but the helicopter continued descending. After maneuvering to a clearing and raising the collective fully, the helicopter impacted the ground heavily. The right-side pilot seat base fractured and collapsed. The trainee pilot received a minor injury; the training pilot was uninjured. The aircraft skid gear, belly panels, and main rotor blades were damaged. No fire occurred, and the emergency locator transmitter did not activate.
Pilot Experience
The training pilot held 5510 total flight hours, with 4300 hours on McDonnell Douglas 369E (HU50) helicopters and about 536 hours on the AS 350-B3. He did not hold an instructor rating, which was not required by regulation. The trainee pilot had 2000 flight hours, including 1850 on turbine helicopters and 500 hours of longline experience. He had completed ground-based familiarization and about 2.5 flight hours on the AS 350-B3; this was his second flight on the type.
Weather and Operations
At the time, weather was cloudy with light rain showers, visibility about five statute miles, wind light and variable, temperature about 3°C. The helicopter, registered in the United States, was operated by Prism Helicopters Ltd. under Canadian Aviation Regulations. The training pilot was assessing the trainee for employment in U.S. operations. No detailed brief on crew duties in an emergency was conducted. At the onset of the limited power condition, both pilots were looking down at the longline and did not observe a red governor light or hear an aural warning.
Post-Accident Findings
After engine shutdown, the red governor (GOV) light was observed. Data from the Vehicle Engine Multi-function Display (VEMD) indicated fault codes: VEMD Code 129 (RED/AMBER GOV F MTR: fuel valve resolver or stepper motor failure) and FAIL 2, 4002 (RED GOV INDICATION: serious stepper motor failure). Eurocopter's analysis concluded a major governor failure occurred, resulting in a fixed fuel condition; no additional power was available when demanded. The Digital Engine Control Unit (DECU) data showed the twist grip remained in flight position. The Rotorcraft Flight Manual procedure for red GOV failure requires moving the throttle lock/flight notch to allow manual fuel control.
Engine examination revealed no foreign object damage, measurable erosion, or metallic debris on magnetic plugs. No fuel system rupture or fire was found. The airframe fuel filter contained brownish material attributed to iron oxide (rust); a fuel sample was clear and bright. The emergency locator transmitter did not activate for undetermined reasons.
Audio Warning System
The helicopter was equipped with a Northern Airborne Technology (NAT) AMS42 intercom system. This system could route aural warnings to both pilot and co-pilot headsets, but the operator chose to enable warnings only for the pilot to avoid alarming passengers in the left seat. The aural warning at the co-pilot seat was not enabled, and no placard indicated this. The pilots did not recall hearing any audible warning or seeing warning lights during the event. The left-seat controls lacked a throttle lock release mechanism, preventing the training pilot from manually controlling the throttle.
Additional Observations
A sliver of O-ring material found in the Hydro-Mechanical Unit (HMU) fuel channels could have obstructed the fuel metering valve, potentially impeding movement and causing a resolver-stepper motor differential, leading to the fixed fuel flow condition. The governor could not deliver increased fuel flow to maintain the hover, resulting in the descent. The left seat's lack of throttle lock release prevented manual override.