Integrity Lessons from the WAAS Integrity Performance Panel (WIPP)

T. Walter, P. Enge, B. DeCleene

Abstract:	The Wide Area Augmentation System (WAAS) is unlike any previous navigation system fielded by the FAA. Historically the FAA has implemented relatively simple and distributed systems. Each only affects a small portion of the airspace and each is maintained independently of the others. WAAS, in contrast, is a complex and centralized, system that provides guidance to the whole airspace. Consequently, the certification for WAAS must proceed very cautiously. WAAS is being pursued because its potential benefits are significant. It will provide guidance throughout the national airspace. It will enable approaches with vertical guidance to every runway end in the United States without requiring local navigational aids. It will enable advanced procedures such as curved approaches and departures. Eventually it will allow greater capacity through smaller separation standards. These and other benefits motivate the effort to create and certify this new type of system. Although the analysis becomes much more difficult, the system must maintain the same or higher level of safety than the existing infrastructure. Another difference with WAAS is that it is inherently a non-stationary system. It relies on satellites that are constantly in motion and that may change their characteristics. Additionally, the propagation of the satellite signals varies with local conditions. Thus, the system has differing properties over time and space. However, the system requirements apply to each individual approach. In particular, the integrity requirement, that the confidence bound fails to contain the true error in fewer than one in ten million approaches, must apply to all users under all foreseeable operational conditions. To ensure that the integrity requirement would be met, the FAA formed the WAAS Integrity Performance Panel (WIPP). The role of the WIPP is to independently assess the safety of WAAS and to recommend system improvements. To accomplish these tasks, the WIPP had to determine how to interpret the integrity requirement for WAAS, develop algorithms to meet this requirement, and ultimately validate them.
Published in:	Proceedings of the 2003 National Technical Meeting of The Institute of Navigation January 22 - 24, 2003 Disneyland Paradise Pier Hotel Anaheim, CA
Pages:	183 - 194
Cite this article:	Walter, T., Enge, P., DeCleene, B., "Integrity Lessons from the WAAS Integrity Performance Panel (WIPP)," Proceedings of the 2003 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2003, pp. 183-194.
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