Accident Details
At approximately 1235 Pacific daylight time, a Liard Air Limited de Havilland DHC-6-100 Twin Otter (registration C-FAWC, serial number 108) was taking off from a gravel airstrip near the Northern Rockies Lodge at Muncho Lake, British Columbia, on a visual flight rules flight to Prince George. After becoming airborne, the aircraft entered a right turn. The right outboard flap hanger contacted the Alaska Highway. The aircraft then struck a telephone pole and a telephone cable, impacted the edge of the highway a second time, and crashed onto a rocky embankment adjacent to a dry creek channel.
The aircraft came to rest upright approximately 600 feet from the departure end of the airstrip. An intense post-impact fire ensued, and the aircraft was destroyed. One passenger suffered fatal burn injuries. One pilot was seriously burned, the other pilot sustained serious impact injuries, and the other two passengers received minor injuries.
Weather Conditions
Weather at Muncho Lake was suitable for visual flight. Sky conditions were high overcast, with cloud bases above the level of the surrounding mountain ridges. Isolated rain showers were moving through the area. The temperature was estimated to be 15°C. The surface wind was described as southeast at approximately two knots, with occasional variations in speed and direction. The aircraft altimeters were set to field altitude prior to takeoff, and the altimeter setting was observed to be 29.95 inches of mercury.
Company Background
Liard Air Limited was a privately owned company offering fixed-wing air services under Sections 702, 703, and 704 of the Canadian Aviation Regulations. The main base was at Muncho Lake, operating in association with Northern Rockies Lodge. The company operated a Cessna 185 on floats, a de Havilland DHC-2 Beaver on floats, a Cessna 172 on wheels, and the accident de Havilland DHC-6-100 Twin Otter on wheels. The Department of Transport air operator certificate authorized Twin Otter visual flight rules operations under Sections 702, 703, and 704, and instrument flight rules operations under Section 704.
Airstrip Characteristics
The company used two gravel airstrips at Muncho Lake. The lodge airstrip was located at Mile 462 of the Alaska Highway, within the highway right-of-way, across from the Northern Rockies Lodge. The airstrip was at 2750 feet above sea level, oriented southeast/northwest. A post-accident survey determined it was about 950 feet long and sloped upward about 2° in the northwest direction. Takeoffs were usually towards the northwest due to high terrain to the southeast. The Alaska Highway crossed diagonally under the climb-out corridor approximately 100 feet beyond the northwest threshold.
A recently decommissioned rural telephone cable was suspended about 25 feet above ground on poles on the opposite side of the highway. Including terrain upslope and pole height, the cable was approximately 47 feet higher than the southeast threshold. The distance between the southeast threshold and the cable was approximately 1330 feet. A gravel road crossed the airstrip at about midpoint, 455 feet from the southeast threshold.
The southeast threshold was unmarked and indistinct; approximately the first 100 feet of surface was covered with grass and short brush. There were no windsocks; flight crews relied on flags flying on tall poles in front of the lodge as wind indicators. The owner considered the airstrip to be 900 feet long. The airstrip had never been professionally surveyed.
Operational Context
Weather conditions were suitable for visual flight, and field examination of the wreckage gave no indication that a pre-occurrence mechanical problem had contributed to the accident. Although the left engine performance was slightly less than the right engine during the takeoff roll, torque pressure on both engines exceeded the expected takeoff power setting of 39.5 psi for the existing temperature and pressure altitude, and propeller rpms compared favorably with normal takeoff values.
Organizational and management factors were noted. The operational control and risk management practices within Liard Air did not recognize and reduce or eliminate the risks associated with takeoffs from the lodge airstrip. The company was in administrative transition due to recent changes in key personnel; the Twin Otter operation was most affected.
Several organizational policies and procedures were either violated, not used, or missing. The Liard Air operations manual required takeoff performance calculations based on aircraft weight, but a weight and balance calculation had been accomplished without using the weight to calculate takeoff performance. Takeoffs from the lodge airstrip had come to be regarded as routine without performance calculation, and aircraft loading was based mostly on intuition and judgement.
Liard Air had an unwritten company policy that the lodge airstrip would be used primarily to store the Twin Otter, and departures from the airstrip would be with crew only and minimum fuel. Records showed this policy was rarely violated, although takeoffs occasionally occurred with heavy fuel loads. On the day of the accident, the takeoff was attempted with three passengers and a full load of fuel, violating the policy in two ways.
Training provided by the owner to the captain emphasized the use of 30° of flap for short-field takeoffs, whereas 10° of flap would have resulted in lesser distance to climb to 50 feet. Considering the elevation, length, slope, and gravel surface, maximum performance short-field (MPS) procedures may have been required for higher weight takeoffs; however, the company and aircraft were not approved for MPS operations, and neither flight crew member had received appropriate MPS training.
The owner was the main decision-maker, familiar with daily operations, highly influential, and experienced with Twin Otter operations on the lodge airstrip. His direct input at the pre-flight planning phase contributed to the flight crew's expectation that the takeoff could be accomplished successfully. There was no standard operating procedure (SOP) for Twin Otter short-field operations to formalize non-MPS limits.
Work Setting and Flight Crew
The work setting at Liard Air differed from corporate or airline environments. Seasonal bush-flying operations rarely have dispatchers, ground crews, locally available maintenance personnel, or highly formalized procedures. Flight crews often rely on local knowledge and are more self-reliant. Operational challenges in confined, short-airstrip environments can be significantly different from those in corporate and airline operations with longer runways and obstacle-free climb-out corridors.
The captain and first officer were the final line of defense. Both were relatively new to Liard Air and lodge airstrip operations. The captain had been hired and appointed chief pilot about five weeks prior. His initial administrative workload and flight duty obligations may have reduced time to experience, recognize, and evaluate risks. Critical information about the accident flight was provided piecemeal, but the captain expected the takeoff would be successful based on his belief that the owner and first officer had discussed and considered the takeoff weight.
The first officer was more familiar with the circumstances, having prepared the aircraft most of the morning. He verbally provided weight and balance information to the captain and placed full responsibility for the decision on the captain. The captain had recently been flying DHC-6-300 series aircraft in the Maldives (float-equipped), which may have conditioned him to anticipate higher performance. Both pilots were aware the aircraft had operated from the lodge airstrip for several years, reinforcing their expectation that the takeoff should be successful.