Safety Performance of Airborne Separation: Preliminary Baseline Testing

Abstract

The Safety Performance of Airborne Separation (SPAS) study is a suite of Monte Carlo simulation experiments designed to analyze and quantify safety behavior of airborne separation. This paper presents results of preliminary baseline testing. The preliminary baseline scenario is designed to be very challenging, consisting of randomized routes in generic high-density airspace in which all aircraft are constrained to the same flight level. Sustained traffic density is varied from approximately 3 to 15 aircraft per 10,000 square miles, approximating up to about 5 times today's traffic density in a typical sector. Research at high traffic densities and at multiple flight levels are planned within the next two years. Basic safety metrics for aircraft separation are collected and analyzed. During the progression of experiments, various errors, uncertainties, delays, and other variables potentially impacting system safety will be incrementally introduced to analyze the effect on safety of the individual factors as well as their interaction and collective effect. In this paper we report the results of the first experiment that addresses the preliminary baseline condition tested over a range of traffic densities. Early results at five times the typical traffic density in today's NAS indicate that, under the assumptions of this study, airborne separation can be safely performed. In addition, we report on initial observations from an exploration of four additional factors tested at a single traffic density: broadcast surveillance signal interference, extent of intent sharing, pilot delay, and wind prediction error. Nomenclature

Impact of Pilot Delay and Non-Responsiveness on the Safety Performance of Airborne Separation

“…Further analysis is required to identify the cause of the 2 resolution failures observed. As it was determined in earlier studies 2 , at traffic densities above 17 aircraft per 10,000 nmi 2 , the three resolution patterns used in computing strategic resolutions appear to provide insufficient maneuver flexibility in a few observed cases. It is hypothesized that the addition of maneuver patterns adds degrees of freedom and would provide the needed flexibility.…”

“…Results from that study indicated that within the experimental conditions and assumptions, safety was preserved with no losses of separation observed for traffic densities much higher than current levels. For the baseline SPAS test runs described in the aforementioned study 2 , ADS-B reception was perfect (i.e., all messages received at all ranges), full aircraft trajectory intent was shared, the pilot responded correctly to all traffic alerts with no delays, and wind predictions were accurate. Results showed that at five times the typical traffic density of today's NAS, utilizing only airborne strategic conflict detection and resolution logic with a 10-minute look-ahead time, safe separation of aircraft can be maintained under the assumptions and conditions of the test.…”

“…During the progression of experiments, various errors, uncertainties, delays, and other variables potentially impacting system safety will be incrementally introduced to analyze the effect on safety of the individual factors as well as their interaction and collective effect. Results from the baseline SPAS study 2 indicate that at five times the typical traffic density of today's National Airspace System (NAS) and under the assumptions of the study, airborne separation can be safely performed.…”

“…The baseline set of runs for the SPAS experiment, completed in the spring of 2007, included scenarios with no system uncertainties or prediction errors 2 . Results from that study indicated that within the experimental conditions and assumptions, safety was preserved with no losses of separation observed for traffic densities much higher than current levels.…”

Experimental Performance of a Genetic Algorithm for Airborne Strategic Conflict Resolution

“…Sustained traffic density was up to about 10 times the traffic density in a typical sector today. 4 This scenario included limited sources of uncertainty (primarily modeling simplifications in the predicted trajectories) and was intended to develop an initial understanding of the safety performance of airborne self-separation and to establish a baseline for comparison with later experiments that add other sources of uncertainty.…”