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facility and found that the TACAN antenna was coated with ice, which, in his opinion, was the cause of the malfunction. However, the TACAN and the VOR are separate pieces of equipment and failure of one in no way affects the other. Since the aircraft was not equipped with DME this feature of the VORTAC facility could not have been utilized. The FAA flight tested the MLS VOR about 0300 the following morning and found it to be operating normally.
Statements were taken from 21 persons who saw and/or heard an airplane in the Miles City area near the time of the accident. Investigation revealed no other aircraft in flight at the approximate place and time except for Northwest Airlines Flight 40, a DC-7C, which reported over Miles City at 2035 en route from Billings to Minneapolis at 17,000 feet. Some of the witnesses were to the southwest of the MLS Airport (along the flightpath from Billings) and some were to the east and northeast.
Three witnesses were able to fix the time of their observation quite closely. One, the technician who was sent to inspect the inoperative TACAN, established that it was 2048 when he saw an aircraft, which he could identify as a DC-3, pass overhead, toward the airport at a height above the ground of approximately 1,000 feet and about 600 feet north of his position. According to the witness, the aircraft appeared and sounded normal at this point. At that time he could see the glow of the rotating beacon at the airport, 3-1/2 miles to the northeast. He also noted weather conditions and estimated that wind gusts were 35-40 knots "or maybe more," that the wind was strong enough to move small rocks on the ground and that the driving snow was very wet. Another witness, who was in a parked car about 3-1/2 miles south of the airport, did not see or hear an airplane but did see a red flash in the sky, ". . . the whole sky to the west was lit up . . ." at a time he established as close to 2050. He noted a gusty wind from the north with snow or sleet. A pilot witness was in his home in Miles City about one mile southeast of the airport. At about 2050, a time established by reference to a television program he was watching, he heard an unusually loud noise from an airplane. This loud noise lasted for five to eight seconds and ended abruptly. He described the weather as moderate wet freezing snow with wind gusts of 30-40 knots.
Other witnesses were not sure of the exact time of hearing or seeing the aircraft. Most of them, however, recalled the state of the weather and expressed it in such terms as "poor visibility, snowing," "heavy wet snow," "swirling snow, wet, heavy, visibility less than 200 feet." The wind was described, in consensus, as gusty up to 45 knots.
Witnesses in Various locations around the VOR Site and airport reported seeing an aircraft below 6,000 feet during the early evening. Others heard an aircraft over the City of Miles City (about one mile southeast of the airport) at low altitude during the same time period.
Runway 30 at Miles City airport is 5,601 feet long, 150 feet wide, and was lighted at maximum brilliance. The airport does not have a control tower. There is no USWB station. FAL maintains a station at this airport and, at the time of the accident, one FAL agent was on duty at the station. The FAA maintains an FSS at the airport and, at the time of the accident, one man was on duty. This individual was certificated by the USWB to take surface weather observations. The ceilings which he reported were obtained by means of a ceiling light projector and a clinometer. The FAA—prepared and USWB-approved visibility reference charts in use at MLS FSS did not include the visibility reference points required to
