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Conclusions
After due consideration, the preponderance of evidence suggests the most logical fact for the loss of control was either the lack of application of sufficient rudder, or an inadvertent release of left rudder for some unknown reason. The delayed corrective action, together with the decision to advance power on the idled engines instead of reducing power on the good engines, permitted the yaw and induced roll to become severe and uncontrollable.
Subsequent to the accident, the FAA discontinued the requirement that Boeing 707 aircraft make actual landings with simulated failure of 50 percent of the power units concentrated on one side of the aircraft during training flights, type ratings, and proficiency checks. These maneuvers may be simulated at an appropriate higher altitude.
On February 5, 1960, Boeing Airplane Company issued a service bulletin approved by the FAA for an improved rudder modification, which adds boost power to the wider ranges of directional movement and gives increased control capability at low air speeds and minimum gross weights. This modification also replaces the original rudder with an improved version.
Although the Civil Air Regulations do not require a flight recorder to be operating during training, test, or ferry-flight operations of a scheduled air carrier aircraft, nevertheless, the flight recorder aboard N 7514A was operating during this training flight and considerable information concerning the maneuver and flight path information just prior to impact was obtained through reduction of pertinent data on the flight recorder tape. Even though the recorder was severely damaged, considerable information was tabulated and graphed to assist the Board in determining a probable cause for the accident.
On January 12, 1960, the Board recommended to the Administrator, Federal Aviation Agency, that flight recorders be installed in all new transport-type airplanes and presently operating turbine-powered transport-type airplanes. Subsequent to that date and as a result of the information gained from the flight recorder in this accident, the Board has expressed the opinion to the Administrator, Federal Aviation Agency, that recorders should also be installed and operating during the training, test, and ferry-flight operations of these air carrier airplanes. It is the Board's belief that in these latter operations, the airplanes are subjected to the same environmental factors and flight loads experienced in scheduled service.
