Page:CAB Aviation Accident Report, Mid-Air Collision on 15 December 1959.pdf/6

- 6 - heading for the Bonanza at impact of 154 degrees magnetic. From.the only known Witness to the collision it was learned that the Bonanza was flown straight and level on a constant heading for a period which he estimated as three to five minutes before the midair impact. Although the witness thought the Bonanza

pulled up and banked left one to three seconds before impact, the structural evidence clearly indicates this either occurred after the collision or it was an illusion created as the two planes of different Sine and Speeds merged and collided. The approximate true airspeed of 139 knots for the Bonanza was based on the manufacturer's Operating data for the aircraft at normal cruise and at 9,000 feet. It is noteworthy that a reasonable variation of this speed factor above or below normal cruise in this instance will not appreciably alter the computed heading of the Beechcraft.

The Cheyenne Municipal Airport is located on the north Side of the city. In addition to being the home base of the Air National Guard Squadron it also serves three scheduled air carriers and considerable general aviation and military traffic. The airport has a conventional five-mile radius control zone and utilises conventional left traffic patterns, one for light aircraft and the other for heavy traffic. The first is close in and the latter is within three miles of the center of the airport. In addition, the F-86L's use a tactical approach and 360-degree overhead landing pattern. All of the patterns were published and disseminated locally. The use of the airport by the Jet fighters and the fact that they made instrument low approaches Was also published in the Airman's Guide according to its publication procedures.

Another factor relative to this collision is that the F-86L flight utilized UHF (ultra high frequency) communications and the Beechcraft was equipped with VHF (very high frequency) communications. The tower did not, nor does any tower normally, simulcast on both VHF and UHF communications. The F-86L pilots and the Bonanza pilot, therefore, could not overhear radio communications made with respect to the other.

From the evidence gathered in the accident investigation it is apparent that the collision occurred outside of the Cheyenne Airport traffic pattern but within the limits of the airport control zone. It occurred while both flights were being made on VFR flight plans and.in weather conditions which were virtually clear; visibility was reported as 90 miles. Under these Circumstances Civil Air Regulations impose upon the pilot direct and full responsibility to avoid collision through visual detection and avoidance of other aircraft. The Civil Air Regulations also state rules regarding right-of-way under various conflicting Situations. Because averting collision rested solely with the pilots it is imperative in accident investigation to determine the Opportunities afforded each pilot to carry out this responsibility. In order to determine and evaluate them it is necessary not only to determine the manner in which the aircraft collided but also the relative position of each aircraft with respect to the other during the 60~second period of closure prior to collision The testimony of the jet pilots, the inflight structural damage to the Beechcraft, and other information gathered during the investigation