Analysis Supporting FAA Decisions Made During the Development of TSO C-129

James P. Fernow and Young C. Lee

Abstract:	During 1992 members of the FAA Navigation Satellite Operational Implementation Team (SOIT) developed Technical Standard Order (TSO) C-129, which describes capabilities of GPS avionics to be used as a supplemental means of navigation for en route through nonprecision approach phases of flight. During the writing of TSO C-129, the SOIT requested that certain analyses be done including the effect of certain types of altimeter aiding on receiver autonomous integrity monitoring (RAIM) availability and the risk of continuing flight in the event of an unpredicted loss of RAIM after an aircraft crosses the final approach fix (FAF) of a nonprecision approach. The results showed that altimeter aiding significantly improved RAIM availability and that the risk of continuing an approach in case of an unpredicted loss of RAIM under certain conditions was acceptable and appeared smaller than the risk associated with a missed approach. Operational and technical considerations including the results of these analyses led the SOIT to require certain capabilities of GPS avionics to be TSO’d under C-129. These include: altimeter aiding with GPS calibration; predicting the existence of the RAIM detection function at future times and locations; and for approach- capable avionics, accepting and using a local barometric pressure setting in RAIM; and delaying the display of a flag in case of an unpredicted loss of RAIM for up to 5 minutes after crossing the FAF under certain conditions.
Published in:	Proceedings of the 50th Annual Meeting of The Institute of Navigation (1994) June 6 - 8, 1994 Antlers Doubletree Hotel Colorado Springs, CO
Pages:	219 - 228
Cite this article:	Fernow, James P., Lee, Young C., "Analysis Supporting FAA Decisions Made During the Development of TSO C-129," Proceedings of the 50th Annual Meeting of The Institute of Navigation (1994), Colorado Springs, CO, June 1994, pp. 219-228.
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