LAAS Ground Equipment Availability

Warren Hundley and Mitch Sams

Abstract:	Availability is not a parameter that has been specified in the past for ILS/MLS ground systems. However, it is an important element of the Required Navigation Performance (RNP) for any landing system. It will be specified for the LAAS SIS (Signal-in-Space) and it will have an impact on the LAAS ground equipment architecture and design. Contributions to unavailability of the LAAS SIS come from both the space segment and the ground segment. In analyzing the availability potential of various GPS augmentations for LAAS, nearly all the emphasis in the past [l-7] has been placed on the space segment performance as related to the availability of a specific vertical accuracy, availability of fault detecting, availability of continuity, etc. However, other than its contribution to vertical accuracy, little attention has been paid to the ground segment’s total impact on availability, particularly with reference to ground system reliability. This may have been acceptable for SCAT-l, which specifies an availability of 0.98% for the ground segment, but it is not valid for LAAS with SIS availability requirements between 0.999 and 0.99999 as defined by the LAAS ORD (Operational Requirements Document [8]. This paper analyzes the four major contributors to unavailability from the ground segment: I. Alarm rate during normal operation 2. Latent design defects 3. Data link propagation corruption 4. System failures a) Equipment b) Service - airport environment Each contributor is considered from the point of view of how it has been treated in the past (ILSMLS) designs and how it impacts the future LAAS requirement and design. Special emphasis is placed on Item 4, which is traditionally where in- depth analysis on ILS/MLS products has been conducted in the past. The relationship of system failures on continuity of function risk, as well as on availability, is also treated. In summary some observations are made on what makes sense for availability requirements for the LAAS ground equipment for various applications and recommendations are offered concerning the ground equipment architecture necessary to satisfy those requirements.
Published in:	Proceedings of the 1997 National Technical Meeting of The Institute of Navigation January 14 - 16, 1997 Loews Santa Monica Hotel Santa Monica, CA
Pages:	463 - 473
Cite this article:	Hundley, Warren, Sams, Mitch, "LAAS Ground Equipment Availability," Proceedings of the 1997 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1997, pp. 463-473.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In