L. Welch Pogue, Edward Warner, Harllee Branch, Oswald Ryan, and Josh Lee for the Civil Aeronautics Board

“ No person, other than a first or second pilot, shall manipulate the controls of an air carrier aircraft while in scheduled flight: Provided, That at the discretion of the first pilot such restrictions shall not apply to authorized inspectors of the Administrator or to properly qualified company personnel or to properly qualified personnel of other air carriers. ”

“ If the unusually high stresses on the horizontal tall surfaces during the pull-up were not due to a so-called "high speed buffeting" condition, it is still possible that some other combination of air loads existed which resulted in a condition severe enough to cause failure of the stabilizer. The horizontal tail structure is designed to withstand the air loads that would be expected under reasonably unfavorable flight conditions, including the loads due both to gusts and to control forces. ”

“ Only mild mechanical turbulence could have resulted from the rough terrain as the wind velocity was very light up to the height of the surrounding mountains. There is no evidence of wind shear turbulence. Considering all of the meteorological factors, there appears to be no reason to believe that the airplane could have been subjected even to a single isolated gust of sufficient severity to cause damage to the structure. ”

“ I had just loosened my seat belt—I hadn't taken it off entirely, but I had loosened it to give myself a little more room to settle in my chair, and was just about to doze off to sleep when I noticed this sudden acceleration as from the nose of the plane being pulled upward very sharply. ”

“ The failure of both the left wing tip and the right stabilizer are of a character consistent with air loads imposed during a severe pull-up. The coincidence of two separate elements of the airplane's structure failing at the same time is unusual, therefore consideration was given to the possibility of the failure of one of them causing the failure of the other. ”

“ There were no known witnesses to the accident from the ground. John Raymond Wilcher, mill foreman, whose home is located in Cedar Valley, about 8 miles north of the scene of the wreckage, testified that he had gotten out of bed on the night of the accident to ascertain whether his son had come home, and he had reason to observe the time, which was 1:05 a.m. He stated that he returned to bed and stayed awake for a time he estimated to have been 10 or 15 minutes when he heard an airplane. ”

“ Furthermore, it was ascertained that the design strength of the stabilizer was such as to require more than a normal force by the pilot to cause failure in a pull-up, provided that the air-load conditions during the pull-up were as anticipated in the design requirements. In view of the above it is concluded that during the subject pull-up unusual and abnormally high air loads prevailed, but the knowledge of their origin and exact nature is limited at the present time. ”

“ The fact that the airplane went out of control and remained so after the pull—up, contrary to the safe landings experienced in the other three cases, also suggests a loss of control, which would naturally result from a failure of some part of the tail. Furthermore the use of flaps during the descent suggests that normal longitudinal control of the airplane was no longer available. It is possible that the crew endeavored to restore longitudinal equilibrium by the use of flaps. ”

“ In at least one of these cases the speed of the airplane at which failure occurred was in excess of normal. In each instance the pilot was able to control the airplane sufficiently to effect a safe landing. From these experiences and from analysis it appears that such failure of the structure in this type aircraft may result either from air loads occasioned in encouraging gusts of extraordinary intensity, or from violent use of the controls. In one of these three instances, the stabilizer also sustained slight damage, insufficient however to render the surfaces inoperative. ”

“ It is reasoned, therefore, that the stabilizer having actually failed, there existed during the pull-up forces other than, or additional to, those normally encountered in such maneuver. Various theories have been explored to explain the presence of such forces.
An analysis of the weather prevailing in the vicinity of Fairfield at the time of the accident does not indicate conditions conducive to turbulence. Except for local ground fog near Salt Lake City, the ceiling and visibility were unlimited along the flight path. ”

“ However, the fact that it was found detached from the remaining portion of the wing panel and has rolled over a few times after the original impact is regarded as significant. Had the wing tip been intact before hitting the ground it is improbable that it would have sustained damage of the type actually incurred by contact with the ground. It is entirely possible therefore that the right wing tip also failed in the air, although there is less evidence to that effect than exists for the failure of the left wing tip. ”

“ The center of pressure on the wings being aft of the c. g. at all normal angles of attack, a diving rather than a stalling tendency may be expected. From the above discussion it is concluded that the wing tip and the horizontal tail surface failures occurred during the same pull-up maneuver (mentioned by Lt. Gardner) , and were not directly dependent upon one another. ”

“ The mechanic remained at the wreckage with the two injured men while Wolfe flew to Fairfield and summoned medical aid from Lehi, Utah. He waited, at Fairfield in order to give a doctor and nurse directions to drive to the scene of the accident. Wolfe stated that he telephoned the CAA office in Salt Lake City at approximately 12:15 p.m. and then flew back to the scene of the wreckage, where he assisted in the rescue work.
Terrain
Fairfield is located about 35 miles almost due south of Salt Lake City, in the approximate center of Cedar Valley, at an elevation of between 4000 and 5000 feet. ”

“ The design of the DC3 and similar model wings reveals that their strength is sufficient to withstand the maximum air loads that the aircraft can normally be expected to encounter, but that the first to fail if the design loads are exceeded will be the structure just outboard, of the wing tip connections, i. ”