What happened
On January 7, 1953, a Douglas DC-4, registration N 86574, was operating as a ferry flight for Flying Tiger Line under a contract with the Department of National Defense. The flight originated in Burbank, California, with an intermediate stop in San Francisco to pick up non-revenue passengers. During the initial leg from Burbank, the crew observed a false fire warning in the number three engine nacelle; however, after mechanical inspections in San Francisco confirmed no actual fire, the aircraft continued its journey toward Seattle.
The flight was cleared to fly via VFR to Williams, California, and then transition to IFR for the remainder of the trip to Boeing Field. During the descent through Oregon, the crew followed instructions from Air Route Traffic Control to descend through various altitude levels. At approximately 20:42, the aircraft reported passing the outer marker at 6,000 feet. Subsequent reports indicated the aircraft was at 4,000 feet and then 3,000 feet.
While approaching Boeing Field, the aircraft was part of a sequence that included a Pan American DC-4 following behind it. After receiving clearance to contact the tower for landing instructions, the Flying Tiger aircraft ceased all radio communication. At roughly 20:55, N 86574 struck the base of Squak Mountain, approximately 11 miles east of the Seattle range station. The impact and subsequent fire resulted in seven fatalities, leaving no survivors.
Findings
Investigations into the accident determined that the primary cause was the aircraft's deviation from the established approach procedure to Boeing Field. Although the weather conditions were instrument meteorological conditions, there were no unusual weather patterns that should have hindered a standard approach. The investigation confirmed that all navigational aids were operating correctly and found no evidence of mechanical failure or fire prior to the impact.