Accident Overview
On a visual flight rules repositioning flight from Pemberton Airport, British Columbia, to Edmonton, Alberta, a Cessna T207A (registration C-GGQR, serial number 20700499) departed at about 1500 Pacific daylight time. The pilot was the sole occupant. The aircraft initially climbed eastward, then turned northeast to follow a mountain pass route. About 30 minutes after departure, the Coastal Fire Service responded to a spot fire and discovered the wreckage in the fire zone. The accident occurred at about 1506 Pacific daylight time.
Wreckage and Site
The aircraft struck trees in a left descending turn with an excess of 30 degrees of bank. The wreckage trail was oriented on a heading 180 degrees from the original flight path. After ground impact, the aircraft slipped down the steep slope, turned around to face its entry direction, and came to rest on its right side. During initial tree impact, an outboard section of the right horizontal stabilizer separated from the empennage. Equipment pods containing lasers detached from the wings and were found about 50 feet behind the main wreckage. Decals on the pods warned of laser radiation when opened, but the laser devices were electrically disconnected for the flight. The engine remained precariously attached to the firewall. A post-crash fire consumed most of the airframe, limiting analysis of flight controls and instrumentation. Two of the three propeller blades were fractured in overload about four inches from the tips; all three blades exhibited leading edge damage, chordwise scoring, and torsion damage, indicating applied power. The emergency locator transmitter was destroyed by impact and fire, and no signal was received.
Weather
Weather recorded by an automatic station at Pemberton at the time of the accident: clear skies; wind 110° true at 4 knots; temperature 28.6°C; dew point 5.3°C; sea-level pressure 910 hPa; altimeter setting 29.80 inHg. Airport elevation 670 feet above sea level; density altitude 2682 feet. Official sunset was at 2136 Pacific daylight time. Mountain weather phenomena such as katabatic winds and rotors were described in the report, but the presence of rotors at the accident site could not be confirmed.
Flight Planning
The flight was conducted under visual flight rules; no flight plan was required, and it is unclear if a person was assigned for flight following. The pilot chose the Duffy Lake road mountain pass route along Joffre Creek at the north end of Lillooet Lake. This route has a steep climb over the first four nautical miles, rising to 4200 feet at ground level in the valley. No radar coverage or navigational aid data were available. A terrain shadow analysis by the TSB Engineering Laboratory determined that the accident site (latitude 50°20′ N, longitude 122°34′ W, elevation about 3280 feet) was at a narrowing point in the initial climb section, on the left side of the valley (southeast-facing slope) that had been in a large shadow region for a couple of hours before the accident. Mountain peaks nearby range from 8550 to 9150 feet asl, with some snow at higher elevations. Using standard lapse rates, the outside air temperature at the accident site at about 3500 feet asl was estimated at 23.1°C, and density altitude 1000 feet above terrain was calculated at about 6319 feet asl.
Pilot Information
The pilot held a valid Canadian commercial pilot licence endorsed for non-high-performance single- and multi-engine land and sea aeroplanes and an instrument rating. He had accumulated approximately 1500 flying hours on light single-engine aircraft, including 75 hours on the accident aircraft in the five weeks preceding the accident. He was provided with a six-page Pilot's Notes document describing modifications and operating techniques, and had received training on the modified aircraft in its least favourable configuration. Company records indicate he recently completed a mountain flying course covering mountain winds and weather, aircraft performance, airmanship, and navigation, with a practical component in a Cessna 172. An autopsy and toxicology examination revealed no condition that could have led or contributed to the accident, and indicated that the pilot suffered post-crash-related fatal injuries. The extent of destruction precluded detailed analysis of injury severity.
Human Factors
The report referenced a New Zealand CAA Mountain Flying booklet describing illusions such as Relative Scale, False Horizons, and Contrast. These illusions may affect judgment of distance and aircraft attitude when flying in mountainous terrain. No specific illusions were confirmed in this occurrence.