History of the Flight
At approximately 1200 Pacific standard time, a Bell 206 BIII helicopter, registration C-GRAH, operated by Westland Helicopters Inc., departed from its base in Houston, British Columbia. The aircraft was on a charter flight to a ski cabin on Mount Morice, about 10 statute miles south of Houston, carrying the pilot, four passengers, and approximately 100 pounds of baggage. The purpose was to transport the passengers and their equipment for a cross-country skiing excursion.
Accident Sequence
The pilot intended to climb above a fog layer in the Houston area by using the rising terrain of Mount Harry Davis as a visual reference. The helicopter commenced flight in marginal visual meteorological conditions. As it climbed the rising terrain northeast of the departure point, visibilities were reduced to a few hundred feet in dense fog. Ear witnesses reported hearing the helicopter collide with terrain; the helicopter did not climb above the fog layer. At some point prior to impact, the helicopter entered a descent, and at impact, it was heading south, away from Mount Harry Davis and back toward Houston.
Investigation Findings
Examination of the wreckage revealed no evidence of pre-impact failure of the engine, controls, or instrumentation systems. The helicopter had been properly maintained, and no flight control difficulties were recorded. Metallic particles were found in the collective servo actuator, but analysis determined that any interference could have been overcome by the pilot. While an aircraft malfunction could not be conclusively ruled out, it was considered improbable. The investigation concluded that the pilot most likely lost visual references with the ground while maneuvering near Mount Harry Davis.
The pilot was experienced in mountain and marginal weather operations but was not trained or qualified for instrument flight. The helicopter was not certified or equipped for instrument meteorological conditions. The visibility along the flight path was reduced to 1/4 mile or less in fog, below VFR criteria. Factors that may have contributed to the loss of visual cues include the pilot's focus on maintaining airspeed, uniform snow-covered terrain possibly creating a whiteout, moisture condensation on the windscreen, and the remote possibility of a control difficulty.
Probable Cause
The pilot, while attempting to climb through a fog layer by using rising terrain as a visual reference, most likely lost the visual cues required for flight in visual meteorological conditions (VMC). The helicopter struck a ridge, probably while the pilot attempted to regain his visual reference with the ground. The pilot's decision to use the rising terrain as a visual reference under the existing visibility conditions was a contributing factor.