A Concept of CAT III GBAS Requirement Based on Real-Time Flight Technical Error Estimation

Naoki Fujii

Abstract:	This paper proposes a CAT III GBAS requirement concept using a real-time Flight Technical Error (FTE) estimation technique. A concept using the real-time FTE estimation technique is already applied to the Required Navigation Performance (RNP) operation with Flight Management System (FMS). FMS calculates the RNP value, the Actual Navigation Performance (ANP) value and the real-time estimated FTE value. ANP is defined as the estimation of the accuracy performance calculated by FMS, which is like a Protection Level of GNSS. This RNP function is easily applicable to GBAS CAT-II/III operation, because GBAS receiver has a capability of real-time FTE estimation. To discuss the merits of this concept compared with the statistical FTE method, the relationship of statistical FTE and Alert Limit (AL) of TSE has to be discussed. The Vertical Alert Limit (VAL) of TSE of CAT-III GBAS is determined by the touchdown box criteria and ILS of Standards and Recommended Practices (SARPs) of International Civil Aviation Organization (ICAO) under very simplified assumptions. I assume that the flare maneuver begins above the height of threshold (16.5m) and so on. Thus the VAL of TSE comes to 12.2 m for the landing short case and 20.0 m for the landing long case at the runway threshold, the VAL of TSE calculated in this way shows a large asymmetry for landing short and for landing long. The concept using the real-time FTE estimation technique is more effective for such a case than for adopting the statistical FTE. Firstly this paper describes the concept using the real-time FTE estimation technique, secondly its applications to GBAS, thirdly the relationship of statistical FTE and VAL of NSE using touchdown box concept, fourthly to determine the VAL of TSE using flare maneuver based on ICAO ILS SARPs, and finally, it describes the determination method of ANP of GBAS.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	453 - 460
Cite this article:	Fujii, Naoki, "A Concept of CAT III GBAS Requirement Based on Real-Time Flight Technical Error Estimation," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 453-460.
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