3. According to the most demanding conditions, the collision risk can be met when the
ideal circling path maintains a 7 km margin with the airspace boundary close to the
air route. In the other directions, since it is not adjacent to the air route, the interval
margin does not need to be too large. According to the calculation of the interval
margin of 7 km in the approaching route and 2 km in other directions, the circling
training airspace size can be set to 22 km  17 km.
References
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2. Brooker P (2003) Lateral collision risk in air traffic systems: a “Post-Reich” event model.
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model. J Civ Aviat Univ China 33:1–4 (in Chinese)
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