A METHOD OF SEPARATION ASSURANCE
FOR INSTRUMENT FLIGHT PROCEDURES
AT NON-RADAR AIRPORTS
 
Sheila R. Conway
Langley Research Center
National Aeronautics and Space Administration
Hampton, VA
 
Maria Consiglio
ICASE
Universities Space Research Association
Hampton, VA
 

Abstract
A method to provide automated air traffic separation assurance services during approach to or departure from a non-radar, non-towered airport environment is described.  The method is constrained by provision of these services without radical changes or ambitious investments in current ground-based technologies. The proposed procedures are designed to grant access to a large number of airfields that currently have no or very limited access under Instrument Flight Rules (IFR), thus increasing mobility with minimal infrastructure investment.  This paper primarily addresses a low-cost option for airport and instrument approach infrastructure, but is designed to be an architecture from which a more efficient, albeit more complex, system may be developed.  
A functional description of the capabilities in the current NAS infrastructure is provided. Automated terminal operations and procedures are introduced. Rules of engagement and the operations are defined.  Results of preliminary simulation testing are presented.  Finally, application of the method to more terminal-like operations, and major research areas, including necessary piloted studies, are discussed.
1 Introduction

In the past few years the limitations of the existing air transport system have become obvious.  Frequent flight delays and cancellations, with all the attendant stress and disruption, are now a familiar part of air travel in the United States.  Many of these difficulties result from the dominant hub-and-spoke model that requires concentration of a large percentage of air traffic at a few airports.  Despite the implementation of improved air traffic management tools and construction of new runways, it has become clear that significant increases in overall air traffic will soon make demands on these airports that simply cannot be satisfied by increasing capacity.1 Moreover, the current focus on capacity problems at hub airports has tended to obscure another fundamental deficiency in the hub-and-spoke system:  the need to change planes.  No one traveling from Milwaukee to Shreveport really wants to drag their carry-on luggage through the terminal at O’Hare; they do so because there is no direct flight available at reasonable cost.  Finally, though most people live in large metropolitan areas serviced by large international airports, there are also many people who would find travel to a small or metro-satellite airport more appealing.  Unfortunately at these smaller airports, viable, cost competitive air transportation is not available.
Because increasing capacity alone does not appear to provide a long-term solution to the problem of delays or satisfy the demand for more direct flights, another line of research has emerged which is aimed at increasing the “mobility” of the system, meaning its ability to accommodate larger numbers of on-demand, point-to-point IFR operations between smaller airports.  This approach complements efforts to increase capacity by promoting more evenly distributed air traffic and reducing congestion at large hub airports.  A number of technologies show promise in increasing mobility:  The use of Automatic Dependent Surveillance-Broadcast (ADS-B) data for surveillance, though still in its infancy, is being proven in the Bethel region of Alaska where ADS-B targets are being used by ATC in conjunction with radar returns to provide separation services2.  The availability of ADS-B data also under-lies development of self-separation tools such as Cockpit Display of Traffic Information (CDTI) and airborne Conflict Detection and Resolution (CD&R) functions that are fundamental to most distributed traffic management proposals.   Methods of augmenting GPS such as Wide Area Augmentation System (WAAS) promise to provide approach capability at airports currently lacking ground-based approach facilities.  Finally, development of aircraft technologies such as small, fuel-efficient turbofan engines, advances in aerodynamics, anti-icing methods, and avionics has resulted in a new generation of small aircraft with seat-mile costs approaching that of transport-category aircraft.
　
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