Senior Air Safety Investigator, and Ray Brown, Air Safety Investigator. Upon the basis of all of the evidence disclosed by the investigation, the Board now makes its report in accordance with the Act.
SUMMARY AND ANALYSIS OF THE EVIDENCE
Air Carrier
At the time of the accident, Northwest was an air carrier operating under a currently effective certificate of public convenience and necessity and air carrier operating certificates. These certificates authorized it to engage in air transportation over Route 3, Chicago, Illinois, to Seattle, Washington, and Winnipeg, Canada, with Bismarck, North Dakota, as one of the intermediate stops.
Airplane and Equipment
Aircraft NC 21711 was a Douglas, model DC3A, manufactured by the Douglas Aircraft Company, Inc. of Santa Monica, California, and purchased by Northwest in 1939. The airplane was powered with two Pratt & Whitney S1C3G engines, and was equipped with Hamilton Standard, constant speed, hydromatic, full—feathering propellers. This model airplane had been approved by the Civil Aeronautics Administration for air carrier operation over the routes flown by Northwest with 21 passengers and a crew of 4. It had been certificated for operation with a standard weight of 24,406 pounds and a provisional weight of 25,200,[1] not including de-icer equipment. The
- ↑ The "standard weight" of an airplane is the maximum allowable weight or landing while the "provisional weight" of an airplane is the allowable weight for take-off. When an airplane takes off with a weight in excess of designated standard weight, the weight of the airplane must be reduced by gasoline consumption prior to arrival at its next scheduled stop, to the extent necessary to bring it within the standard weight for landing. If sufficient gasoline has not been consumed between the time of take-off and any emergency landing, gasoline can be dumped by the use of tested and approved dump valves in order to reduce the total weight to the approved weight for landing. At the time of the accident, the weight of the airplane had boon reduced well below its authorized standard weight.
