THC was the prime factor.
Flight operations in remote areas such as Canada's North–west Territories often are unconventional when compared with those in areas crisscrossed with busy airways, airports with precision approaches at both ends and border-to-border radar coverage. In the hinterlands it is not uncommon for the pilot of a scheduled commercial flight to manage all flight dispatch duties himself.
Such was the case at Air Tindi. The operator provides scheduled passenger and freight flights to and from its base in Yellowknife, Northwest Territories, usingCaravan 208Bs under CAR Subpart 703. In addition, it's authorized to use single-engine aircraft for transportation of passengers under IFR and day and night VFR.
The company's self-dispatch system delegates operational control of flights to the pilot-in-command. In October 2011, crews were afforded latitude to conduct scheduled passenger operations under VFR. Under this system, the PIC was responsible for ensuring that appropriate documents including flight plans are prepared and filed prior to departure.
At 0800 on Oct. 4, 2011, a young Air Tindi pilot flew Cessna Caravan C-GATV on a regularly scheduled flight from Fort Simpson, Northwest Territories (CYFS) to Yellowknife as Air Tindi Flight 222. The VFR commercial flight arrived at 0919 without incident despite spotty marginal weather and a possible violation of airspace rules.
Fort Simpson weather at 0800 recorded visibility of 6 mi. in light rain and mist, broken clouds at 300 ft. and an overcast at 1,500 ft. The Caravan entered clouds shortly after takeoff and remained in clouds cruising at 3,900 ft. for most of the flight. Thus the trip was flown in IMC above the floor of controlled airspace at 2,200 ft. AGL in which an IFR clearance was required.
The next leg for this pilot was to depart Yellowknife with three passengers at 1100 for a regularly scheduled flight to Lutsel K'e located some 106 mi. due east. The company operations manual contained a published route with a minimum IFR altitude of 3,100 ft. ASL. This provided a minimum of 2,000 ft. of terrain clearance from the highest elevation of 1,100 ft., which was about 26 mi. west of Lutsel K'e. Most of the route lay in uncontrolled airspace, and an ATC clearance was not required. The airport was served by an RNAV instrument approach with a minimum straight-in LNAV descent altitude of 1,160 ft. ASL, or 567 ft. AGL. It was left to the pilot to decide whether to go VFR or file IFR.
The Yellowknife-Lutsel K'e region that day was under the influence of a trough of warm air aloft. The system generated overcast layers from 2,000 to 4,000 ft. ASL with tops at 24,000 ft. ASL. Scattered altocumulus castellanus topped at 22,000 ft. ASL. Predicted localized visibilities were from 3 sm to more than 6 sm in light rain showers and mist, and patchy ceilings were from 800 to 1,500 ft. AGL. Moderate mixed icing was predicted above the freezing level at 5,000 ft. AGL.
The terminal forecast for Yellowknife, valid for 24 hr., from 0600 was available to the pilot before departure. For the period of the flight, the forecast called for wind, 120 deg. at 12 kt.; visibility, more than 6 sm in light rain; a few clouds at 600 ft. AGL and a broken cloud cover at 1,500 ft. agl. Occasionally, the visibility was to be 3 sm in light rain and mist, with clouds broken at 600 ft. AGL. A revised forecast, issued at 1102, predicted essentially the same conditions, with a temporary lower broken cloud height of 500 ft. AGL.
The 1100 METAR for Yellowknife reported wind, 110 deg. at 12 kt., gusting to 18 kt.; visibility, 3 sm in light rain and mist; sky condition, 500 ft. AGL broken, 1,000 ft. AGL overcast; temperature 6C, dewpoint 5C. Stratocumulus covered most of the sky.
When Air Tindi 200 departed Yellowknife at 1103 under a VFR clearance, the visibility was at the VFR minimums of 3 sm. VFR operations within the control zone were allowed without requiring a special VFR clearance. Once en route, clear of the Yellowknife control zone and below 1,000 ft. AGL, the aircraft was required under Canadian Aviation Regulations to remain clear of clouds with flight visibility not less than 2 sm. Investigators would determine later that the flight to the Lutsel K'e area was conducted on a direct track at low level, below a low, ragged cloud base into reducing visibility.
The last radio call heard from the Caravan was a position report indicating the flight was about 20 mi. from Lutsel K'e. The pilot reported none of the usual information such as arrival intentions and estimated time of arrival. The crew of another aircraft that also was inbound to Lutsel K'e from Yellowknife heard this radio report.
The Air Tindi Caravan failed to arrive at its scheduled time of 1145. The company's representative at Lutsel K'e alerted the Yellowknife operations center at 1223. The last known position appearing on the Air Tindi headquarters SkyTrac database indicated that C-GATV had stopped short of Lutsel K'e, and the company emergency response plan was activated at 1245. Two company fixed-wing aircraft were dispatched on visual and electronic searches. Neither the Joint Rescue Coordination Center nor search aircraft received an ELT signal.
Ultimately, a rescue crew in a float-equipped de Havilland DHC-6 located the wreckage at 1420 and landed on nearby Great Slave Lake. The crew hiked into the accident site and arrived at 1530. The pilot and one passenger were dead. Two passengers suffering serious injuries were shuttled by helicopter to the floatplane and evacuated to Yellowknife at 1800.
The aircraft had crashed some 26 nm west of Lutsel K'e near the crest of Pehtei Peninsula. There was no post-impact fire.
Investigators from Canada's Transportation Safety Board (TSB) surveyed the scene and wreckage. The terrain between Yellowknife and Lutsel K'e consists of gently rolling, tree-covered Canadian Shield rocky outcrops, with interspersed lakes. Ground elevation on the route varied from 600 ft. to 1,100 ft. ASL. The accident site was near the highest point on the route, rising about 500 ft. from the surface of Great Slave Lake. The peninsula is oriented nearly perpendicular to the aircraft's flight path to Lutsel K'e. The first point of impact was at an elevation of 1,013 ft. ASL, about 38 ft. below the top of the peninsula and 20 ft. above the face of a vertical cliff.
At impact, the aircraft was in a nearly level attitude in pitch and roll. First ground impact was by the landing gear, followed by the belly cargo pod and the propeller, all of which separated from the aircraft at this point. The airplane continued up a 10-deg. slope over the top of the hill, became airborne and came to rest inverted 477 ft. down the eastern slope of the peninsula. The cockpit was crushed, and the forward passenger cabin was distorted, with the forward cabin bulkhead mostly dislodged from its attachments. The left wing had folded back and rested on the ceiling of the cabin.
The airplane had been equipped with a SkyTrac GPS-based flight-following system that transmitted aircraft position, altitude, groundspeed and track via satellite link to the company at subscribed 15-min. intervals. The onboard equipment recorded this data at 5-sec. intervals. The 5-sec. interval data were extracted by the TSB laboratory and used to reconstruct the accident flight. The last SkyTrac transmission at 1140 showed the aircraft at rest, indicating the time of the accident.
After takeoff from Yellowknife, the pilot flew a direct track to Lutsel K'e with slight variations in groundspeed and track. Altitude varied between 850 ft. and 1,470 ft. ASL. Aircraft height above ground level varied between 129 ft. and 600 ft. One minute before its impact, the aircraft was at 1,325 ft. ASL, or 500 ft. AGL, 136 kt. ground speed and tracking 091 deg. Immediately before impact, altitude was 1,060 ft. ASL, the ground speed was 141 kt. and track was 098 deg.