Northern Air Cargo

Douglas DC-6

The crew was conducting a GPS instrument approach in a Douglas DC-6B airplane under IFR conditions. Both pilots were certificated and type-rated in the Douglas DC-6B airplane. The first pilot, seated in the right seat, was one of the company's senior check airman, and possessed a right seat dependency endorsement. The second pilot, seated in the left seat, had less experience in the DC-6B airplane. It had been previously agreed that the second pilot would fly the leg of the flight on which the accident occurred. The first pilot reported that light snow showers were present, with visibility reported at 4 miles. During final approach as the airplane passed over the airstrip threshold, a higher than normal sink rate was encountered. He said that the initial touchdown was "firm," but was thought to be within acceptable tolerances. Just after touchdown, the left wing broke free from the airplane at the wing to fuselage attach point. The airplane veered to the left, continued off the left side of the 5,000 feet long by 75 feet runway, down an embankment, and came to rest in an area of wet, tundra covered terrain. A postcrash fire heavily damaging the center section of the fuselage. The cockpit voice recorder (CVR) revealed that as the airplane progressed along the approach, the first pilot says: "You're only one mile from it....Take it on down ah three." As the airplane passes over the runway threshold, the first pilot says: "Keep that, keep that (expletive) power off.... Just push forward on the nose." The sound of impact is heard 4 seconds later. The minimum descent altitude (MDA) for the approach is 400 feet msl (383 feet agl). A contract weather observer reported lower ceilings, with about 1 mile visibility, over the approach end of the runway at the same time as the accident.

Douglas DC-6

The cargo flight was en route, when a fire erupted in or near the #3 engine. During subsequent emergency procedures, the flight crew pulled the fire handle first. Later, they feathered the #3 engine. The fire did not extinguish. During an attempt to land at a rural, intermediate airstrip, while the airplane was in the traffic pattern, witnesses saw fire coming from the area of the #3 engine. They stated the right wing buckled upward, and the airplane crashed. Examination of the wreckage revealed a failure of the master rod in the front bank of cylinders of the #3 engine. Metallurgical tests revealed a crack in the top of the master rod head, which had resulted from corrosion pits. The side of the master rod head was measured and found to be out of round. The master rod shank also fractured due to fatigue. The operator's training procedures and the Douglas Aircraft emergency checklist procedures, required that the engine's propeller be feathered first, and then the fire extinguishing system to be activated. According to information derived from the airplane's cockpit voice recorder, the flight crew reversed that order. The effectiveness of the fire suppression system is diminished if the propeller is not feathered first.