Required Navigation Performance Flight Management Systems (FMS) RNP is a navigation system that provides a specified level  of accuracy defined by a lateral area of confined airspace in  which an RNP-certified aircraft operates. The continuing  growth of aviation places increasing demands on airspace  capacity and emphasizes the need for the best use of the  available airspace. These factors, along with the accuracy of  modern aviation navigation systems and the requirement for  increased operational efficiency in terms of direct routings  and track-keeping accuracy, have resulted in the concept  of required navigation performance—a statement of the  navigation performance accuracy necessary for operation  within a defined airspace. RNP can include both performance  and functional requirements and is indicated by the RNP type.  These standards are intended for designers, manufacturers,  and installers of avionics equipment, as well as service  providers and users of these systems for global operations.  The minimum aviation system performance specification  (MASPS) provides guidance for the development of airspace  and operational procedures needed to obtain the benefits of  improved navigation capability.  [Figure 9-41] The RNP type defines the total system error (TSE) that  is allowed in lateral and longitudinal dimensions within  a particular airspace. The TSE, which takes account of  navigation system errors (NSE), computation errors, display  errors and flight technical errors (FTE), must not exceed the  specified RNP value for 95 percent of the flight time on any  part of any single flight. RNP combines the accuracy standards  laid out in the ICAO Manual (Doc 9613) with specific accuracy  requirements, as well as functional and performance standards,  for the RNAV system to realize a system that can meet future  air traffic management requirements. The functional criteria  for RNP address the need for the flightpaths of participating  aircraft to be both predictable and repeatable to the declared  levels of accuracy. More information on RNP is contained in  subsequent chapters. The term RNP is also applied as a descriptor for airspace,  routes, and procedures (including departures, arrivals,  and IAPs). The descriptor can apply to a unique approach  procedure or to a large region of airspace. RNP applies to  navigation performance within a designated airspace and  includes the capability of both the available infrastructure  (navigation aids) and the aircraft. RNP type is used to specify navigation requirements for the  airspace. The following are ICAO RNP Types: RNP-1.0,  RNP-4.0, RNP-5.0, and RNP-10.0. The required performance  is obtained through a combination of aircraft capability and  the level of service provided by the corresponding navigation  infrastructure. From a broad perspective: Aircraft Capability + Level of Service = Access In this context, aircraft capability refers to the airworthiness  certification and operational approval elements (including  avionics, maintenance, database, human factors, pilot  procedures, training, and other issues). The level of service  element refers to the NAS infrastructure, including published  routes, signal-in-space performance and availability, and air  traffic management. When considered collectively, these  elements result in providing access. Access provides the  desired benefit (airspace, procedures, routes of flight, etc.). RNP levels are actual distances from the centerline of the  flightpath, which must be maintained for aircraft and obstacle  separation. Although additional FAA-recognized RNP  levels may be used for specific operations, the United States  currently supports three standard RNP levels: RNP 0.3 represents a distance of 0.3 NM either side of a  specified flightpath centerline. The specific performance that  is required on the final approach segment of an instrument  approach is an example of this RNP level. At the present  time, a 0.3 RNP level is the lowest level used in normal  RNAV operations. Specific airlines, using special procedures,  are approved to use RNP levels lower than RNP 0.3, but  those levels are used only in accordance with their approved  operations specifications (OpsSpecs). For aircraft equipment to  qualify for a specific RNP type, it must maintain navigational  accuracy at least 95 percent of the total flight time. A flight management system (FMS) is not a navigation  system in itself. Rather, it is a system that automates the  tasks of managing the onboard navigation systems. FMS may  perform other onboard management tasks, but this discussion  is limited to its navigation function. FMS is an interface between flight crews and flightdeck  systems. FMS can be thought of as a computer with a large  database of airport and NAVAID locations and associated  data, aircraft performance data, airways, intersections,  DPs, and STARs. FMS also has the ability to accept and  store numerous user-defined WPs, flight routes consisting  of departures, WPs, arrivals, approaches, alternates, etc.  FMS can quickly define a desired route from the aircraft’s  current position to any point in the world, perform flight  plan computations, and display the total picture of the flight  route to the crew. 9-44 • RNP 0.3 – Approach • RNP 1.0 – Departure, Terminal • RNP 2.0 – En route