Flight Tests of the Microwave Landing System Multimode Digital Processor.

Abstract : Flight tests were performed in order to evaluate four digital airborne processing techniques. Four techniques used for processing Microwave Landing System (MLS) time reference scanning beam (TRSB) signals are: (1) dwell-gate processing (DGP), (2) single-edge processing (SEP), (3) dual-edge processing (DEP), and (4) splitgate processing (SPGT). These techniques were flight tested under standard partial orbits, glide slopes, and aircraft shadowing. Overall, the SPGT and DGP techniques resulted in about the same errors. The SEP data were noisier than the DGP but usually had about the same bias. The DEP technique was always inferior to the DGP. Aircraft shadowing errors were excessive for all techniques and should be avoided by operating procedures when an aircraft nears the touchdown region. It is recommended that the DEP algorithm be changed for improved noise performance and flight tests be performed using all four processing techniques in a specular multipath environment and under conditions using two azimuth antennas having different beam widths (these tests were not performed because of equipment nonavailability during flight testing). (Author)