Autolanding a 737 Using GPS Integrity Beacons

This paper describes how differential GPS (DGPS) and miniature, low-cost Integrity Beacon pseudolites were used to carry out 110 successful automatic landings of a United Airlines Boeing 737 aircraft. These autopilot-in-the-loop flight tests using GPS Integrity Beacons (low-power, ground-based marker beacon pseudolites placed under the approach path) furnished evidence that GPS can provide the full performance necessary to meet the stringent specifications of Category III. The built-in geometrical redundancy provided by Integrity Beacon ranging is coupled with centimeter-level accuracy to provide the system integrity. This integrity—calculated to be better than one part in a billion probability of missed detection—is achieved independently from ground-based monitors using receiver autonomous integrity monitoring (RAIM).