Estimated Time Of Arrival (ETA) performance system comparative evaluation

As the United States (U.S.) moves toward the various phases of Next Generation Air Transportation System (NextGen), there will be more emphasis on control of aircraft using time as well as the traditional speed control. With this in mind, Radio Technical Commission for Aeronautics (RTCA) was directed by Federal Aviation Administration (FAA) in 2012 to revisit the Minimum Aviation System Performance Standards (MASPS): Required Navigation Performance (RNP) for Area Navigation (RNAV), DO-236B [1], to update the requirements for RNP RNAV systems based on lessons learned from implementing Performance Based Navigation (PBN). The committee was also asked to consider a forward look/refinement of the time-based requirements for systems. The RNP RNAV system performance standard DO-236C [2] Change 1 [3] amended existing standards from DO-236B by expanding the minimum requirement for system computed Estimated Time of Arrival (ETA) in a Flight Management System (FMS). The new minimum functional requirement is that the ETA must be available for each fix in a flight plan; the previous minimum only required ETA at the “go to” fix. In an important addition, DO-236C Change 1 sets a minimum performance requirement on ETAs at all planned (future) fixes in the onboard flight profile. Thus the standard has been expanded both in the functional and the performance requirements for ETA in an RNP RNAV system.