Safety Study of Closely Spaced Parallel Operations Utilizing Paired Approach

The paired approach (PA) concept is one that leverages the real-time navigation and communication capabilities of the Federal Aviation Administration's (FAA) NextGen Automatic Dependent Surveillance-Broadcast (ADS-B) equipage initiative to increase airport capacity by performing simultaneous dependent approaches to parallel runways with centerlines spaced at least 700 feet (ft), but less than 2,500 ft apart. Two primary hazards associated with a PA are collision risk and wake encounter risk. This paper analyzes collision risk in the event of a course deviation by the lead aircraft to determine the closest in-trail distances deemed acceptable for the operation. These distances are referred to as collision safety limits (CSL). Experimental methods employed utilized fast-time simulations to assess collision risk. Additionally, new methods for the development and analysis of the fast-time simulations were applied. Results indicate major factors contributing to the CSL include the difference in speed between the lead and trailing aircraft, runway centerline spacing (RCLS), and the type of runway approach alignment (i.e., straight-in or offset). Reduction in CSL in-trail distances is achieved for PA operations with smaller RCLS, straight-in approaches, or where the lead aircraft is flying faster than the trailing aircraft (referred to as aircraft pair speed expansion).