Everts Air Cargo (Everts Air Fuel)

The flight crew was returning from off-loading their cargo at a remote site on the west side of a mountain range. The return flight would provide an option of following a lower mountain pass, or flying over the mountainous terrain. Witnesses related that prior to the flight's departure, the marginal VFR weather conditions began to deteriorate very rapidly, with winds in excess of 50 knots, lowering ceilings, rain, and turbulence. An airmet, valid during the time of the accident, forecast high winds, mountain obscuration, and turbulence. The wreckage of the airplane was located near the crest of a 2,900 feet msl ridge. Wreckage debris was scattered on both sides of the ridge, and the airplane was destroyed by the high speed impact. Inspection of the wreckage disclosed no evidence any mechanical anomalies. A radar track analysis of a target airplane believed to be the accident airplane, depicted a track on a direct route of flight over the mountains from the departure airport towards the destination airport. Altitude data was not received from the target airplane's Mode C transponder, and therefore was extrapolated from the less reliable radar plot information. The maximum altitude plotted was approximately 10,800 feet, prior to a descent as the airplane neared the west side of the range. Mountains along the route of flight exceed 10,000 feet msl.

The heavily loaded fuel tanker landed with an approximate 3 knot tailwind, overran the departure end of the runway, and came to a stop on a frozen river. The last two thirds of the 3,150 feet long gravel runway was covered with ice. The crew stated that the propellers either failed to go into reverse, or were slow in reversing, to assist in stopping. Examination revealed that all propeller blades were in the reversed position. Outside air temperature was minus 30 to minus 35° F. The airplane performance chart used to calculate the landing distance was for 'concrete runways'. Stopping distance was not predicated on the use of reverse propeller thrust. Post accident calculations, using the same chart, found the estimated landing distance needed for the accident flight to be 100 to 200 feet more than the length of the runway.