Analysis of advanced Flight Management Systems (FMS), Flight Management Computer (FMC) field observations trials, Radius-to-Fix path terminators

The differences in performance of various manufacturers' flight management systems (FMSs) and their associated flight management computers (FMCs) have the potential for significant impact on the air traffic control system and as such need to be examined and reexamined. While area navigation (RNAV) and required navigation performance (RNP) procedures and routes are designed according to criteria contained in Federal Aviation Administration (FAA) orders, FMC manufacturers build their systems in accordance with Minimum Aviation System Performance Standards (MASPS) and Minimum Operational Performance Standards (MOPS) for area navigation systems, Technical Service Orders and Advisory Circulars. Despite the disconnect it is anticipated that the resulting performance of the aircraft FMC will meet the procedure design requirements identified in the FAA criteria. The goal is procedures where aircraft operations meet expectations for repeatability and predictability to levels of performance sufficient to support performance based operations in the National Airspace System (NAS). Sometimes, due to the nearly independent development of procedure design criteria and aircraft performance standards, the paths of various aircraft on the same procedure do not overlap and do not match the expectancy of the procedure designer. Studies referenced in this paper such as Assessment of Operational Differences Among Flight Management Systems, Analysis of Advanced Flight Management Systems (FMSs), Analysis of Advanced Flight Management Systems (FMSs), FMC Field Observations Trials, Lateral Path, and Analysis of Advanced Flight Management Systems (FMSs), FMC Field Observations Trials, Vertical Path have shown that these differences may result from any or all of the following: variations in FMC equipment installed on the aircraft; variations and errors in procedure coding in the FMC navigation database; variations in aircraft to FMC interface and associated aircraft performance capabilities; and variations in flight crew training and procedures. The basic FMCs built by the major manufacturers and installed as the core of the FMC/FMS combinations in various airframe platforms will perform differently and this paper attempts to quantify those differences. It focuses on standard performance-based public RNAV (RNP) instrument approach procedures with coded ARINC Navigation Systems Database Specification 424, Radius-to-Fix path terminators (RF), also labeled as RF leg types, and their variations in performance. Criteria currently allows the use of RF leg types only in RNP Special Aircraft and Aircrew Authorization Required (SAAAR) procedures. A Trial Plan was developed and controlled field observations trials were made using eleven test benches at seven major FMC manufacturers. The focus is on RF path terminators used in public procedures at Long Beach Daugherty Airport, California, and follows previous analysis of manufacturers' FMC lateral navigation (LNAV) path conformance described in Analysis of Advanced Flight Management Systems (FMSs), FMC Field Observations Trials, Lateral Path and analysis of vertical navigation (VNAV) path conformance described in Analysis of Advanced Flight Managements Systems (FMSs), FMC Field Observations Trials, Vertical Path. It is hoped that the results of this research will contribute to the eventual acceptance of RF usage in Basic RNP and RNAV criteria.