Test Results of an F/A-18 Automatic Carrier Landing Using Shipboard Relative GPS

Under the U.S. Department of Defense’s Joint Precision and Landing System (JPALS) program, the Navy is responsible for developing the shipboard component, termed Shipboard Relative GPS (SRGPS). As part of the SRGPS effort, a test bed was developed to demonstrate air traffic control, navigation, and landing capabilities in the carrier environment. During flight testing from January through April, 2001, the Navy conducted automatic landings to the USS Theodore Roosevelt (CVN-71) using an F/A-18A Hornet test aircraft. These tests represented several firsts in the history of GPS. In January 2001: • First ever GPS-based precision approach to a US Navy ship (first to any ship by a tactical aircraft), • First ever GPS-based automatic low approaches to any ship, • First ever 3-dimensional GPS guided approaches to any ship, and • First real time demonstration of GPS centimeter level relative accuracy during shipboard approaches. In April 2001: • First ever GPS-based automatic landings at sea. The airborne segment of the SRGPS combined the uplinked GPS data from the ship with data from the aircraft’s onboard GPS receiver to compute a highly accurate Relative Kinematic Carrier Phase Tracking (RKCPT) solution. The airborne SRGPS guidance and control processor blended the RKCPT position solution with data from the aircraft’s Inertial Navigation System (INS) and the shipboard’s Ship Motion Sensor (SMS) to compensate for deck motion and to compute glidepath deviations. The system then provided autopilot commands to the aircraft relative to the ship’s stabilized glidepath, allowing fully automatic precision approaches and landings. This paper will describe the overall SRGPS test effort. The paper will also give an overview of the test bed hardware, as well as results for navigation sensor error, flight technical error and total system error. The test and analysis results support the feasibility of the GPS based precision approach and landing system concept.