Factors influencing blind conflict risk in en route sectors under free-flight conditions

We develop a simulation model of the flight of aircraft through an en route sector. The model is used in two experiments. The first studies the effect of directional clumping on risk. The second is a full factorial design with replication, which simulates a large number of scenarios to assess the impact of key input factors on free-flight risk measures. We measure risk for a given flight by the mean distance of closest approach to other aircraft and the mean number of approaches closer than a specified distance. Using analysis of variance and regression analysis, we determine that the most important influences on blind collision risk are time of entry into the sector and number of aircraft. Also influential are certain orientations of flight paths and the distribution of airspeeds. The least important factor is altitude. The relationship between number of aircraft and the two risk measures can be quantified in regression relationships.