Ohio University/FAA Flight Test Demonstration Results of the Local Area Augmentation System (LAAS)

Local Area Augmentation System (LAAS) flight tests were conducted at the William J. Hughes Technical Center using an FAA-operated Boeing 727 aircraft. This demonstration represents the first full-scale testing of the proposed LAAS architecture and verifies the accuracy and integrity monitoring fimction of the FAARTCA LMS design. ‘fhe LAAS, as implemented for the tests, consists of three multipath-mitigating antenna systems, six narrow-correlator GPS C/A-code receivers, and supporting processors. Transmission to the aircraft of the LMS GPS differential corrections and integrity information is accomplished using the Very-High Frequency (VHF) navigation augmentation broadcast signal (NABS) – a time-division, multiple-access (TDMA) broadcast signal specifically designed for ground-to-air data communications using frequencies in the upper VHF Omni-Range (VOR) band. In the aircratl, the NABS-transmitted ditTerential corrections are combined with GPS data from two narrow-correlator C/A-code receivers to produce a redundant aircraft position. The aircraft position is derived from carrier-smoothed code measurements. The results of the flight tests demonstrate the feasibility of . key components of the LAAS architecture, including the multipath-lirniting antenna system, the implementation of the integrity equations, and the use of the VHF data broadcast. Data processed from 45 approaches results in differential GPS sensor accuracies of 0.46 meters (957.) vertical and 0.22 meters (950A)cross-track on a 3-degree glidepath at a height of 100 feet above the ground.