Page:Aviation Accident Report, United Air Lines Flight 4.pdf/13

- 12 - banked to the right about five degrees at the time. The course taken by the airplane following the first impact also indicates a possibility that the airplane was in a slightly nosed-up attitude when it struck the hillside. It may be that the pilot saw the ground at the last moment and endeavored to avoid it by starting a climbing turn in the right. The testimony of one witness that he heard the engines being "gunned" a moment before the crash occurred tends to support that hypothesis.

We have been unable to determine definitely the reason for the change in direction which carried the airplane into the hillside. No indication of any malfunctioning or failure of any part of the airplane could be found, nor was there any evidence or external interference of any kind. Despite the difficulty of understanding how, under the circumstances, a pilot could make such a substantial deviation from the proper course merely through inadvertence, every available indication leads to the conclusion that this is the most probable explanation that can be made. Such inadvertence may have been either of two kinds, namely, the pilot may have been unaware of the deviation and consequently under the impression that he was continuing on the course on which he had been flying, or he may have changed his course purposely but on an erroneous assumption.

It is extremely, hard to conceive that a change in course of at least 25 degrees could have been imperceptible to the pilot, and, if it were imperceptible initially, that it would not have been discovered promptly. It is equally difficult to believe that the pilot could have changed his course intentionally, since he had been following the radio range leg