Estimating the Vertical Collision Risk of Aircraft Pairs Flying on Crossing Routes

Abstract

For efficient aircraft operation, the implementation of reduced vertical separation minimum (RVSM) is planed for the domestic airspace in Japan. Prior to the implementation, safety assessment was carried out using the collision risk model. The vertical collision risk of aircraft pairs flying on the crossing routes, N_<az>(cross), was estimated under several assumptions. Occupancies estimated in the current 2,000 ft separation environment were assumed to be retained in the RVSM environment. The height keeping performance of all aircraft is assumed to meet the vertical overlap probability of 1.7×10^<-8>. Occupancy values for crossing routes E_z^<cross>(θ) were calculated based on flight plan data obtained from January 2003 through March 2005. Horizontal overlap probability P_h(θ) and horizontal average relative speed h(θ) were also calculated. Using these values together with known values, the collision risk N_<az>(cross) was estimated monthly. The results obtained are as follows. (1) The highest value of monthly collision risk is 1.32×10^<-10>[accidents/flight hour] of November 2003. (2) This value is equivalent to about eleven percent of the collision risk for the same and opposite direction traffic N_<az>(s+o).