Aviation Safety Letter 4-2003

See Fit to Make It — Another Classic

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On December 31, 2001, at 13:17 mountain standard time (MST), a Cessna 172N with a pilot and three passengers on board departed Fort Good Hope, Northwest Territories, on a return flight to Tulita, via Norman Wells. The aircraft did not arrive at Norman Wells and a search was initiated at 15:00 MST. Due to environmental conditions, the wreckage was not found until the afternoon of January 2, 2002, 30 NM south of Fort Good Hope at the 1 100-ft level of a 1 400-ft mountain. The right front seat passenger was fatally injured by the impact. The pilot and rear seat passengers survived the impact with non-life-threatening injuries, but succumbed to hypothermia. This synopsis is based on the Transportation Safety Board of Canada (TSB) Final Report A01W0304.

The planned flight was from Tulita to Norman Wells, then to Fort Good Hope, and a return to Tulita via Norman Wells. There are three main routes normally flown between Norman Wells and Fort Good Hope (see illustration): a direct route along the airway with a minimum en route altitude (MEA) of 5 300 ft, a "river route" along the Mackenzie River, and a "winter road route", which follows the road between Norman Wells and Fort Good Hope. These last two are longer and to the west of the direct route, but are preferred during marginal weather conditions. The winter road route crosses higher terrain than the river route, but it has more emergency landing areas. The river route traverses the lowest terrain of all; however, pilots frequently have problems in winter with low visibility when fog fills the valley around the open water at the Sans Sault Rapids.

The pilot checked the weather and departed Tulita at approximately 10:00 MST. On arrival to Norman Wells, the weather was below VFR conditions and the pilot requested and was approved for a special VFR (SVFR) arrival; he landed at approximately 10:20 MST. The pilot entered the Flight Service Station (FSS) for a weather update, but before the briefing was complete, he left to supervise the refueling. Meanwhile, another Cessna 172 departed Norman Wells under SVFR for Fort Good Hope. This aircraft returned after following the winter road for about 15 NM; this pilot issued a pilot weather report (PIREP) stating that the visibility and ceiling were decreasing to treetop level, and that the airframe and windshield had picked up a layer of ice. The pilot of the C-172N received the PIREP as he was departing Norman Wells, but decided to proceed anyway and left under SVFR for Fort Good Hope. The aircraft passed each other a few miles west of Norman Wells on the north side of the winter road.

As expected, the pilot encountered marginal weather conditions en route and reportedly attempted different routes through the high ground along the winter road. He diverted to the river route, and the aircraft finally arrived in Fort Good Hope 30 min late. On landing, the aircraft was observed to have about 1/2 to 1 in. of ice on the leading edges of the wings and tail surfaces, and about 1/2 in. of ice on the windshield.

The forecast for the period called for patchy broken stratocumulus cloud based at 1 500 to 2 500 ft ASL, topped at 6 000 ft. It also called for local ceilings of 500 ft AGL, with intermittent visibilities of 2 to 6 SM in light snow showers and local visibilities of 1 SM in mist. The icing, turbulence, and freezing level forecast predicted local moderate mixed icing in stratus, otherwise light rime icing in cloud. A cold front situated on an east-west line north of Fort Good Hope at 11:00 MST was moving southward at 10 NM per hour. The 09:00 METAR for Norman Wells included an overcast ceiling of 400 ft AGL, while the 09:00 METAR (corrected) for Fort Good Hope included had light snow showers, overcast ceiling at 1 100 ft and frost on the indicator.

On arrival at Fort Good Hope, the pilot entered the CARS at the airport, but did not consult the operator or PIREPs for a weather update. He telephoned the company base at Tulita and filed a flight itinerary with another company pilot for the return trip to Tulita, remarking that the weather en route was marginal, and that his plan was to follow the river ("IFR"). The pilot was aware that another pilot had departed VFR from Fort Good Hope and returned because of adverse weather conditions, and he discussed the possibility of aborting or delaying the flight.

The pilot then removed ice from the aircraft, the three passengers boarded the aircraft, and the pilot started the engine and taxied out for departure. As he was taxiing, he received a call from the pilot of a Douglas DC4 on approach to Fort Good Hope, advising him of IFR conditions in Norman Wells and icing conditions en route. He acknowledged the information from the pilot of the DC4 and departed Fort Good Hope at approximately 13:15 MST. The aircraft was not certified for flight in known icing conditions. Examination of the wreckage showed that the aircraft struck the mountain in straight and level flight at low speed, and fell about 50 ft down the slope where it became entangled in trees. A layer of rime ice was evident on the wing struts.

The pilot was certified and qualified for the flight and had a current instrument rating. He had a total of 650 hr flying time, with about 460 hr on type, and he had flown to Fort Good Hope 11 times in the previous months. He had completed the contaminated surfaces examination, which acknowledged the requirement for an aircraft to be equipped and certified for flight into icing conditions. The company operates on the pilot self-dispatch system. It stated that there was no urgency for the flight or pressure on the pilot to undertake any portion of the flight. The passenger from Fort Good Hope to Tulita was an entertainer who was to perform at a New Year's Eve party that evening.

Analysis — The location of the accident site suggests that the pilot had flown directly south from Fort Good Hope to intercept the river valley upstream of Sans Sault Rapids, bypassing the rapids. Based on the information gathered, it is probable that the pilot encountered icing conditions and reduced visibility in snow showers or cloud. Since the wreckage remained intact and three of the occupants survived the direct impact with non-life-threatening injuries, the pilot was most likely flying at low airspeed. Perhaps he was intentionally flying slow and low in an attempt to maintain or regain visual reference with the terrain. The cruise flight configuration and the straight and level aircraft attitude at impact are consistent with a CFIT accident.

The pilot's limited experience was adequate to understand the associated risks and implications of operating the aircraft in these adverse weather conditions. He had flown numerous times in the area and was familiar with the terrain and the main and alternative "IFR" routes between Tulita and Fort Good Hope. Under the company's self-dispatch system, the pilot was responsible for determining whether the flight could be conducted safely. As there was no urgent requirement to complete the trip, it could not be determined why many of the decisions made by the pilot were not consistent with his training or accepted practices and airmanship, such as the following:

  • he departed Norman Wells with a SVFR clearance when a current PIREP described en-route weather conditions as being below VFR limits, with known icing conditions;
  • he persisted in attempting passage along the higher ground of the winter road instead of returning to Norman Wells;
  • he entered the CARS but did not update weather information, despite adverse conditions;
  • he disregarded information and advice from experienced pilots prior to departure from Fort Good Hope; and
  • he landed at Fort Good Hope with a considerable amount of airframe icing, removed the ice, then departed back into known icing conditions.

The TSB concluded that the pilot flew into known weather and icing conditions, for which the aircraft was neither equipped nor certified, when there was virtually no chance of completing the flight safely and in accordance with associated regulations. The pilot flew into the side of a mountain for reasons related to ice accumulation and/or reduced visibility in snow showers or cloud.

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