Evaluating eLORAN as a backup for surveillance and navigation: A comparative cost analysis

Over the past five years, there have been multiple studies related to backing up the Global Positioning System (GPS). The studies have mostly focused on technical and operational issues and often assumed a performance requirement that eliminated conventional ground-based navigation aids as a solution. This paper is focused on Enhanced Long Range Navigation System (eLORAN) as a backup for cooperative surveillance and area navigation (but not precision approach) and it is directed at the business case. The authors examined a scenario where conventional ground-based navigation aids are the backup for GPS and where a limited set of secondary radars is a backup for Automatic Dependent Surveillance-Broadcast (ADS-B). This scenario was compared with a case where eLORAN is a backup for GPS, both for navigation and ADS-B positioning, and no ground-based navigation aids or secondary radars exist, with the exception of some Instrument Landing Systems (ILSs) at major airports. Several versions of the eLORAN scenario were examined, varying the year in which eLORAN becomes the backup and when equipage begins in aircraft. In addition, sensitivity analyses were run by varying the costs of the ground-based systems and the avionics. The results indicate that strictly from a cost avoidance perspective, the savings of eliminating Secondary Surveillance Radars (SSRs), Very High Frequency Omni-directional Range (VORs), and Distance Measuring Equipment (DMEs) are smaller than the aggregate costs associated with maintaining eLORAN and the avionics costs to the users. This result is quite robust with respect to variations in the ground and avionics costs. However, if the requirement for a more robust backup than that provided by VORs, DME, and secondary radar can be made, then the case for eLORAN could be made on those grounds. Thus, the question of eLORAN as a backup rests with a better understanding of future requirements and not with cost avoidance.