Analysis of Coast Times upon Loss of GPS Signals for Integrated GPS/Inertial Systems

In aircraft navigation, the complementary characteristics of a Global Positioning System and an Inertial Referencing System can be integrated such that a coasting capability can exist for the aircraft, even if GPS signals are lost. This paper presents an analysis of coast times for a tightly-coupled GPS/IRS and a loosely-coupled GPS/IRS using high quality inertial sensors. The objective is to determine if they can meet the Federal Aviation Administration (FAA's) requirements for three coasting scenarios which are thought to provide potentially significant operational benefits. A variety of conditions regarding flight profile and user-to-satellite geometry, as well as previously established assumptions, are given consideration in the analysis. Results from the analysis reveal that the tightly-coupled integration is able to meet the requirements for two of the three coasting scenarios, but the loosely-coupled integration is not able to meet any of the three scenarios.