Cessna 207 Skywagon/Stationair

The pilot in command's improper inflight planning/decision and his attempt to fly VFR through imc conditions. Factors contributing to the accident were the snow, whiteout conditions, and darkness.

Detonation (or pre-ignition) in the n°1 cylinder, which resulted in erosion (burning) of the n°1 piston and subsequent loss of engine power. A factor related to the accident was: the lack of suitable terrain for an emergency landing.

Inspection of the engine determined that it was capable of developing full power at the time of the accident. The throttle cable was found to have separated from the cast bronze throttle control lever at the fuel/air metering unit on the intake manifold. The serrated steel bush in the throttle control lever at the cable attachment had become loose, causing the hole to wear elongated which reduced the edge distance from the hole to the end of the control lever sufficiently for it to fail when the throttle was opened. This probably occurred during the last takeoff. During flight, the bush, which was still attached to the cable ball end by the bolt, was probably in such a position as to operate the lever when the throttle control was moved to reduce power for climb and cruise. As the flight progressed and the cable separated from the lever, in-flight movement and vibration would have moved the throttle towards the closed position, with the subsequent reduction in power. Further inspection found that the assembly of the cable to the lever was incorrect, with the washer from under the bolt head being omitted. This reduced the bearing area at the bolt head to the control lever, with the possibility that the bolt may have only been clamped to the bush assisting any movement of the bush in the lever. Once the steel bush started moving in the softer bronze material the rate of wear would have been rapid. The aircraft had flown 85 hours since the last periodic inspection, at which time it may have been possible to detect the first signs of wear between the bush and the control lever if information advising of this type of fault had been available.
The following factors were considered relevant to the development of the accident:
- Incorrect assembly of the washers on the control cable attachment bolt may have allowed the bush to start moving in the lever.
- The bush became loose in the control lever, with the subsequent wear elongating the hole allowing the control lever end to fail.
- The throttle control cable separated from the throttle control lever.
- The throttle closed sufficiently during flight to reduce engine power.
- The aircraft was too heavy to maintain flight.
- The aircraft was operating over an area unsuitable for a forced landing.
- Wear between the bush and the lever may have been detectable during the previous periodic inspection if advisory information had been available.

The pilot-in-command's attempt to fly under visual flight rules while in instrument meteorological conditions. Contributing factors to the accident were the low ceiling and surrounding mountainous terrain.

Improper adjustment of the turbocharger absolute pressure controller, and improper manipulation of the power plant controls by the pilot during the go-around. Factors related to the accident were: failure of company management to properly train the pilot in accordance with the approved company training program, and the pilot's lack of experience in turbocharged engine operations.

Failure of the #4 connecting rod. Factors related to the accident were: the adverse weather conditions and lack of suitable terrain for a forced landing.

The mid-air collision occurred because neither pilot saw the other aircraft in time. Causal factors were the pilot's restricted cockpit vision, a lack of pilot awareness to maintain an effective look-out; the unnecessarily high density of traffic and the unplanned merging of two streams of aircraft after a weather deterioration necessitated a change in route after departure.