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This drag, coupled with any appreciable thrust from the No. 3 engine, would force the left wing down. In view of the limited aileron control available, considerable right rudder would be required to induce a yaw to the right to assist in holding the wing up. However, with the rudder boost inoperative, there would not be sufficient rudder control available to induce enough yaw to counteract these forces. It is therefore apparent that the No. 3 engine was shut down prior to impact so as to be able to keep the wings level with the minimum amount of control available. This is also supported by the fact that the engine had almost stopped rotating at impact.
When the aircraft hit the trees on the north bank of the river and a 16-foot section of the left wing was severed, the control available was insufficient to maintain the wings level. As it crossed the river, the aircraft rolled rapidly to the left to a bank angle of approximately 55 degrees and crashed on the south bank.
Conclusions
The Board concludes that this accident was the result of the structural failure of the Nos. 1, 2, and 4 nacelle pylons, and the fire in the area where the No. 2 nacelle broke off. It also concludes the nacelles failed as a result of overloads imposed on them during several violent uncontrolled gyrations which were encountered when the pilot—trainee applied improper control movement in an attempt to recover from a Dutch Roll.
The Board further concludes that the instructor-pilot initiated the Dutch Roll to an angle of bank far in excess of the limitations imposed by the company. In addition, the instructor-pilot was fully aware of these limitations and was, in fact, reminded of them during this flight. Even so he permitted the pilot-trainee, who was on his first training flight, to attempt recoveries from these extreme maneuvers.
It concludes that after control of the aircraft had been regained, Mr. Baum had selected an excellent clear area for the imminent crash landing but failed to make it by one-half mile because the No. 3 engine had to be shut down prematurely to keep the wings level.
Subsequent to the accident the company revised its training syllabus to reduce the possibility of recurrence of a similar accident. The limitations on angle of bank for the Dutch Roll maneuver have been re-emphasized to all company pilot personnel. In addition, Dutch Roll familiarization has been delayed so that the pilot-trainee will have more experience in the aircraft prior to attempting this maneuver.
The company has also incorporated a full-time boosted rudder system in the aircraft. In addition, it has increased the vertical stabilizer area and has added a ventral fin. These changes are anticipated to substantially increase the low speed control characteristics of the aircraft.
