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said that they saw the flight north of the field and before clearing it both controllers scanned the entire area for other traffic. Seeing none, the flight was cleared. The minimum altitude for an ADF instrument approach is 1,900 feet (600 feet above the ground). The controllers said that, based on previous observations of simulated instrument approaches, the flight appeared to be at this minimum altitude but that the speed was considerably faster than would be normal. They said the normal ADF instrument approach as on runway 13, heading 130 degrees, but that this pass was made from north to south across the airport and not aligned with any runway.
Several other witnesses, who were pilots, were in substantial agreement that the F-84's crossed the field at the same approximate altitude as most other aircraft on simulated instrument approaches.
All the witnesses to the accident said that the formation flight proceeded from north to south and after passing the south edge of the field began a turn to the left. The witnesses, some of whom were in the vicinity of the control tower, said the PA-22 appeared to be in straight and level flight on an easterly heading until the collision.
The collision occurred approximately two miles south of the Mansfield Airport, well within the control zone. The PA-22 was proceeding in a northeasterly direction and the F-84F in a southerly direction. The angle formed by the intersection of the flight paths was approximately 78 degrees. (See Attachment "A"). In addition, the F-84F was in an angle of left bank approximately 30 degrees relative to the longitudinal axis of the PA-22. These relative angles of impact were determined by evidence of deformation and damage to the PA-22 wings, cabin area, engine, and engine mounts, and the F-84F right wing, pylon tank, aft fuselage, and empennage.
A review of the records of both aircraft indicates that they had been maintained in airworthy condition. There were no discrepancies or carryover items affecting the airworthiness of either.
The weather conditions at the time of the collision were broken to overcast clouds at 3,500 feet; visibility 22 miles; wind southeast at 4 knots.
Analysis
In VFR weather conditions, primary responsibility for collision avoidance rests with each pilot. In addition, it is expected that pilots will exercise extreme caution when operating in a control zone or in the vicinity of an airport. In this instance the pilot of the PA-22 should have notified the Mansfield tower of his position in the control zone. While this is not required by Civil Air Regulations, it is, in the exercise of sound judgment, a good operating practice to follow in an area of traffic concentration.
A study of the angle at which these airplanes approached one another revealed that both of the pilots of the PA-22 and the leader of the F-84F formation had ample opportunity to see and avoid each other. It is assumed that the PA-22 was on a straight and level course for at least a minute prior to the collision. (See attachment "A"). The sighting angle from the lead F-84F to the PA-22 was approximately 19 degrees to the right of the nose. The sighting angle from the PA-22 to the F-84F formation was approximately 74-1/2 degrees to the left of its nose. These computations are based on relative speeds and the angle of impact and the sighting angle
