Page:CAB Accident Report, Northwest Airlines Flight 5.pdf/16

 sult did not direct Captain Bates to proceed to his alternate.

16.

The action of Captain Bates in continuing his descent over Fargo after encountering more severe icing conditions than had existed at cruising altitude was not consistent with good operating practices.

Probable Cause

Upon the basis of the foregoing findings and of the entire record available at this time, we find that the probable cause of the accident to aircraft NC 21712 (Northwest Airlines' Trip 5) on October 30, 1941, was the failure of the aircraft, when the inboard portions of the wings were stalled, to respond to the application of full power in the manner reasonably to be expected in the light of the aeronautical knowledge then available.

Contributing Factors

1.

Accumulation of ice on the wings and other surfaces of the airplane, increasing the stalling speed and the drag of the airplane on the power required to maintain flight.

2.

Failure of the captain, due to his having lost confidence in the air-speed mete to realize his close approach to a stalled condition.

3.

Action of the captain in descending to attempt a landing at Fargo with known icing conditions and critical ceiling conditions, instead of proceeding to an available alternate.

4.

Failure of the dispatcher to recognize the seriousness of weather conditions in the vicinity of Fargo and to direct the pilot to proceed to his alternate.

Comment

1.

Because the investigation of this accident, and the tests described herein, appeared to have revealed a flight characteristic of the DC-3 airplane which had not been recognized, the Board, shortly after the tests were conducted, circulated to the industry the information then available with respect to the observed effects of the application of full power under the conditions described and the apparent indispensability of depressing the nose of the airplane in order to reduce the rate of descent even after the application of full power. As we have indicated earlier herein, further studies are being made for the purpose of explaining the behavior of the airplane. Any further information, discovered during the study, which may appear to be helpful to the industry likewise will be circulated.

2.

It appears that the practice of letting down to "take a look", when weather conditions at the point of intended landing are officially reported to be less than prescribed minimums, may at times create a serious hazard. Accordingly, the Civil Aeronautics Board is now considering a regulation which would prohibit that practice.