Utilizing RNAV avionics: testing lateral offset procedures

In recent years as demand for air traffic services has increased, the Federal Aviation Administration (FAA) has sought new ways to use airspace more efficiently while maintaining safety. A recent initiative, headed by Air Traffic RNP Division (ATP-500), wanted to explore the use of advanced area navigation (RNAV) avionics, specifically, the lateral offset (LO) feature of the flight management computer (FMC). With this capability, a pilot can, with a few simple button pushes, execute a maneuver whereby the aircraft turns off-course (either left or right) and flies to intercept a parallel path from the original route. The original route may later be rejoined. It was thought that this onboard capability might have some applications that would allow more expeditious flow of air traffic. Continental Airlines had expressed a desire to use the LO feature, and stepped forward s the lead operator to participate in testing the procedure. It was decided that a reasonable location for the testing would be a superhigh altitude sector somewhere in the western U.S., avoiding the congestion and heavy reliance on route structuring of the eastern and central U.S. The Albuquerque and Houston Air Route Traffic Control Centers (ARTCCs) were identified as good candidate for this. On 23 July and 4 November 2002 tests were conducted. This article describes potential applications and benefits of the LO procedure, discussing the onboard avionics pilot interface and some of the differences in the way various FMCs/aircraft may process LOs, and describes the actual testing of the procedure.