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which comprise the link assembly-clevis attachment were undamaged. Stress analysis data and tests by the National Bureau of Standards conclusively proved that had an AN5-12 bolt been in place in the attachment, high impact forces could not have sheared the bolt but would have badly damaged the components. It is on this irrefutable physical evidence that the Board concludes the AN5-12 bolt which normally secures the link assembly clevis attachment was not in place when the aircraft crashed.
In addition to the above it is the Board's opinion that the recovered bolt is not evidence that a bolt of the required specification for the attachment, one of recent use, and one with markings matching the bearing bore and clevis forks, was left in the tail during previous maintenance. On the contrary, it is the Board's opinion that this is evidence that the bolt was the one holding the attachment together immediately prior to the accident. Considering the inflight jostling, the forward forces when the aircraft struck the runway, and the aft forces when the tail toppled to the runway, it is entirely possible for the bolt to have reached the location where it was found.
In view of the aforestated analysis and conclusions, it is the judgment of the Board that the bolt worked out of the attachment, causing the loss of elevator control. It follows that the bolt could have worked out only because it was improperly secured, a condition which had to exist and should have been discovered when the No. 2 maintenance inspection was made less than two flying hours before the accident. In the opinion of the Board it also follows that, had the inspection of the attachment been performed by the inspector as he described it, the insecurity of the bolt would have been detected.
In its conclusions the Board has carefully considered the radio transmissions made by Captain Bagus, the important portions of which have already been quoted, together with the reasons for their importance. While the Board would agree that the meaning of the transmissions is not entirely clear, it would not agree that they are subject to the single interpretation that Captain Bagus had elevator control when the autopilot was engaged. In light of the circumstances and physical evidence, the Board believes that the most reasonable interpretation is that all pitch control was lost except that which could have been obtained from power and trim and that this condition was not altered by using the autopilot.
It is clear that Captain Bagus did use the autopilot but not that its use restored the lost elevator control which was initailly reported. It is believed that the pilot used the autopilot for lateral and directional control in combination with power and trim for pitch control. This is suggested when Captain Bagus said, "This autopilot is not too easy to operate in this manner." The words "in this manner" particularly suggest the combination, the autopilot itself not being hard to operate in the normal manner.
That longitudinal control was not provided by the autopilot is clearly suggested when Captain Bagus was using the autopilot and transmitted, "Am going to try dropping my gear pretty soon to see if I can maintain tail trim." Also, when he said, "Have to make a pass or two and get my power
