Benefit of Tightly Coupled GPS/IRS for RNP Operations at Terrain Challenged Airports
James McDonald
2:30 PM on 2008-04-25
209 Akerman Hall
Benefit of Tightly Coupled GPS/IRS for RNP Operations at Terrain Challenged Airports Abstract RNP procedures are particularly beneficial for airports that are surrounded by high mountains. Unfortunately, such procedures using unaugmented GPS receivers are occasionally unavailable because the mountains mask low elevation satellites to the extent that GPS receivers can't provide adequate integrity for the procedure. This presentation demonstrates how the Honeywell IRS/GPS Hybrid (HIGH) dramatically improves availability for low RNP operations at terrain challenged airports. The presentation focuses on RNP approach/departure availability for four of the most terrain challenged airports currently using RNP operations: Linzhi, Tibet; Queenstown, New Zealand; Aspen, Colorado; and Quito, Ecuador. Analysis was performed via simulations which implement a high fidelity terrain database which provides masking information for all points along a trajectory. Data was studied for terrain masking under the nominal state of the current GPS almanac along with an impact analysis on availability when satellites become unavailable during planned/unplanned outages. Field test results are presented that corroborate the analysis. Both simulation and field test results show that by tightly integrating GPS and IRS data, the HIGH algorithm outperforms the GPS receiver under nominal conditions and is also significantly more robust to poor satellite geometry.