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The left horizontal stabilizer and elevator were sooted and heat wrinkled on the upper and lower surfaces. In addition, the severe fire from the left wing burned through the upper skin between the internal stiffeners.
Three of the four powerplants, with a major part of their pylons attached, separated from the aircraft in flight. They were found one to one and one—half miles northwest of the main wreckage. The Nos. 1 and 4 engines, with their nacelles, broke from the airplane in the outboard directions. The No. 2 engine, with its nacelle, broke partially outboard but appeared to have rotated downward and rearward during its separation from the aircraft. The No. 3 engine remained attached to the aircraft until impact. It was found at the main wreckage site. Investigation revealed that there were little or no indications of inflight fire damage to engines Nos. 1, 3, and 4. However, the cowling which fell with the No. 2 engine showed evidence of heavy smoke and sooting prior to impact.
The damage found on all four engines was the result of impact or minor ground fire. No evidence of operational distress or malfunction prior to impact with the ground was found. In addition, indications were found on all four engines that they were rotating very slowly, if at all, at impact.
During the public hearing a Boeing witness testified that pilots who have had an engineering background or test-pilot experience in the Armed Forces are selected as test pilots for Boeing. These pilots are then given extensive ground school training and flight experience under the supervision of instructor-pilots. He said before a pilot could be released as an instructor he had to have a check ride and approval by the Chief of Flight Test or his designee. He further stated that Baum had met all of these requirements and was considered fully qualified to conduct this particular flight.
The witness then described the company checkout and training program for airline personnel. He said the airline pilots would have had the 707 training syllabus for a considerable length of time prior to the beginning of flight training and would also have completed the ground school courses. A briefing would be conducted prior to flight which was a general review of the entire training syllabus. Immediately before each flight an additional briefing would be held to cover item by item the maneuvers to be accomplished.
The witness stated that the Dutch Roll characteristic is present in all large aircraft but is more pronounced in those with swept-back wings like the 737. It is most likely to be encountered during approach to landing when the aircraft is at slow speed with a high coefficient of lift and in rough or turbulent air. He said the characteristic constituted a minor annoyance to pilots and slight discomfort to passengers and it was therefore desirable to give instructions in recovery technique. All Boeing flight personnel had been informed that the desired maximum roll-bank angle in this maneuver was 15 degrees and that the absolute maximum was 25 degrees. These restrictions were not imposed because of a structural limitation on the aircraft, but because the maneuver and its recovery could be satisfactorily demonstrated with these conservative limitations. Subsequent to the accident Boeing re-emphasized the roll-bank angle limitations and deleted demonstration of the maneuver with flaps down because recovery can be demonstrated equally as well in the clean configuration. In addition, the Dutch Roll training has been moved back in the training program so that the trainee will be more familiar with the characteristics of the airplane when the maneuver is demonstrated.
