Overview of the Safety Analysis of Loran for Aviation

The Loran Integrity Performance Panel (LORIPP) completed its 18 month study of the ability of Loran to meet aviation requirements for Required Navigation Performance 0.3 (RNP 0.3) in March 2004. The study examined Loran ability to meet on the RNP 0.3 requirements on integrity, availability, and continuity and provide a design for “enhanced Loran” which would allow Loran to reasonably provide RNP 0.3. This is the first time Loran integrity has been examined in the depth required for aviation. The integrity requirement in turns affects availability and continuity since it sets the acceptable levels of parameters used for determining availability and continuity. The paper presents and details the major results on integrity, availability and continuity of the analysis for RNP 0.3. The integrity analysis is the first step to the overall requirements analysis since it drives the performance levels and bounds that Loran must meet. The integrity fault diagram illustrates how each hazard could affect integrity. It also provides for the calculation of the overall integrity by tallying the integrity allocations for each hazard. The bounds and parameters used to determine availability are established by the integrity allocation for each hazard. Using the bounds and performance parameters set by integrity, availability and continuity can be calculated. Since Loran performance can vary significantly from location to location, a coverage tool was developed to carry out these calculations throughout the coverage area. These results represent a statement of the availability and continuity of a Loran system that meets RNP 0.3 integrity requirements. The entire process is iterative. For example, unacceptable availability may lead to a refinement in procedures or allocation so that a lower bound may be achieved while still satisfying integrity.