Availability performance comparisons of combined Loran-C/GPS and standalone GPS approach navigation systems

Operational air navigation systems not only must provide adequate position estimates, but they also must be available to the user when needed, and able to warn the user in a timely manner when the system becomes unusable. The paper addresses the availability of a combination Loran-C and GPS radionavigation system during nonprecision approach (NPA). Also, GPS by itself cannot meet the sole means integrity requirements for NPA. Simulation models were developed to quantify statistically the availability of the Loran-C/GPS system and to compare it with GPS alone. The results presented in the paper show that the combination Loran-C/GPS navigation system enhances the availability of either standalone system by at least a factor of ten. Loran-C also enhances the integrity of GPS. Loran-C can use the same approach geometry and cockpit display instruments now allowed for GPS