Panel question submitted by James L. Farrell

James L. Farrell

Abstract:	This question involves the possibility of airline disasters traceable to an incorrect signal in space (SIS) from GPS. An errant SIS can occur roughly once per year; that is a nominal estimate, based on a limited number of years of operation with GPS. In the mid-1990s it was envisioned that augmentation systems would be available (and therefore provide needed integrity) before widespread usage of GPS for flight. Increasing usage before satisfaction of all augmentation performance requirements draws attention to Integrity Monitoring: Receiver Autonomous Integrity Monitoring (RAIM) is a sophisticated and highly developed technique for checking SIS validity operationally in real time. In order to ensure proper functioning of that "safety net" tests are conducted. Although FAA Technical Standard Orders (TSO) contain clear and specific requirements for integrity, the procedures for testing the performance of a GPS receiver are only partially standardized. Specifically, integrity tests on the final receiver product are left to the interpretation of the manufacturer. Unfortunately, most of those suppliers had little or no participation in RTCA activities where these sophisticated issues were addressed. Possibility of an unsophisticated design failing at a crucial time (i.e., with errant SIS) cannot be dismissed. Potential consequences inescapably include the presentation of misleading navigation information to several aviation users at the same time, resulting in one or more accidents. It is important to avoid any alarmist tone here; this is a highly unlikely occurrence. Although unlikely on any given day, however, many days translate into multiple chances; the industry cannot substantiate that this prospect is wildly implausible - - and, given the stakes, it needs to be wildly implausible; outlandishly remote. Standardized testing by eminently qualified experts at a site such as CIGTF could provide the necessary validation. Since the condition just identified is not now a reality, a question arises: Given the awareness of this situation by several individuals and organizations in the GPS community as well as the existence of documentatin providing an example of misinterpreted certification test procedures, what are the liability implications for FAA, for the airlines, for the airframe manufacturers, and for the equipment suppliers in the event of an accident?
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	1420 - 1420
Cite this article:	Farrell, James L., "Panel question submitted by James L. Farrell," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 1420-1420.
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