Airborne Spacing and Merging in the Terminal Area: a Human-in-the-loop Simulation

Due to the natural compression of aircraftdecelerating in preparation for landing, current-dayair traffic control operations in terminal areas arecharacterized by several clearances, including speedinstructions and heading vectors. These operationsoften create excess spacing between consecutiveaircraft, which adds an extra buffer to the safetymargin, but reduces the number of aircraft that canland at an airport over a period of time. Havingaircraft equipped with advanced cockpit tools thatcan utilize Airborne Separation Assistance System(ASAS) clearances like 'merge-behind-then-follow'could increase system performance by minimizingin-trail spacing buffers. Providing air trafficcontrollers with Decision Support Tools (DSTs) thataccommodate such a strategy could further improvesystem performance. In August 2004, NASA AmesResearch Center conducted a simulation of ASASoperations. Analyses of the simulation data suggestthat airborne spacing and merging operations areacceptable to controllers and reduce excess spacingbetween aircraft.