AARO GoFast Case Resolution (mirror)

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Determining the object’s true speed and direction of travel (heading) requires knowing the F/A-
18F’s heading. AARO calculated the object’s speed and heading relative to the aircraft because
the video display does not contain the aircraft’s heading. AARO calculated the object’s position
and direction of travel for the entire range of possible wind directions (0° - 360°) to account for
differences in atmospheric conditions between the F/A-18F’s altitude and object’s altitude. This
comprehensive modeling informed AARO’s assessment of whether the object moved with or
against the wind and whether it behaved anomalously for all possible directions of travel.
AARO factored in historical wind speeds and directions at both the object’s altitude (13,000 feet)
and the aircraft’s altitude (25,000 feet), as measured near the time and location of the event:
• At 13,000 feet, wind speed was 30.9 m/s (69 mph) from the west (265°).
• At 25,000 feet, wind speed was 52 m/s (116 mph) from the west southwest (255°).
Figure 1 shows the object’s range of possible speeds calculated while compensating for wind
speed at 13,000 feet. This is considered the “intrinsic” speed. An intrinsic speed of 0 m/s
indicates that the object is moving with the wind, or about 30.9 m/s.
Figure 1: The y-axis represents the object’s speed with wind effects removed. The x-axis represents the
wind’s heading relative to the F/A-18F’s airframe geometry (0° is a headwind). The curve represents the
object’s range of speeds at each angle. The tailwind, headwind, and crosswind cases are denoted by the
colored lines. The object’s lowest possible speed occurs near a headwind while the highest occurs in a
tailwind.
Figure 2 shows the object’s range of possible headings relative to the wind direction at 13,000
feet. A direction of 0° indicates that the object is moving in the same direction as the wind.