RNP 10 ➔ 4 RNP 0.3 ➔ 0.1 RNP 5 ➔ 1 RNP 12 ➔ 4 RNP 4 RNP 4 RNP 10 ➔ 4 FLIGHT OPERATIONS JEFF AIMAR RNP 10 ➔ 4 ASSOCIATE TECHNICAL FELLOW AIR TRAFFIC MANAGEMENT SERVICES BOEING COMMERCIAL AIRPLANES GROUP AERO 26 REQUIRED NAVIGATION PERFORMANCE FOR IMPROVED FLIGHT OPERATIONS AND EFFICIENT USE OF AIRSPACE equired navigation per- beacons. See “Traditional and Area INDUSTRY EXPANSION OF Technical Commission for Aeronautics formance (RNP) extends Navigation” on p. 34.) 2 ICAO RNP (RTCA) and the European Organisation for 2 x RNP R the capabilities of modern ICAO defined RNP as “a statement of While the ICAO definition of RNP Civil Aviation Equipment (EUROCAE)— airplane navigation systems by the navigation performance accuracy adequately specified 95 percent accuracy expanded the definition of RNP to include providing real-time estimates of necessary for operation within a performance, it did not quantify other a new lateral containment limit and defined airspace.” This navigation navigation uncertainty, assurance common navigation parameters normally minimum navigation system capabilities. performance accuracy is quantified of performance through its con- used by industry during equipment design These additional requirements are with two values: a distance in nautical tainment concepts, and features and certification. It also lacked a way to documented in the “Minimum Aviation miles (known as the RNP type) and RNP that ensure the repeatability and System Performance Standards (MASPS): a probability level. For example, an statistically specify potential rare excur- predictability of airplane naviga- Required Navigation Performance for airplane is qualified to operate on an sions from the desired path. Two aviation tion. This precise characterization Area Navigation,” issued by the RTCA. RNP 10 airway if it has demonstrated standards organizations—the U.S. Radio of airplane performance is key to that the capability and performance designing more efficient airspace of the airplane navigation system will ICAO RNP 10 EXAMPLE routes and procedures. result in the airplane’s being within 1 FIGURE Before introducing RNP operations 10 nmi of the indicated position RNP RNP into their fleets, operators should on the navigation system at least 95 percent of the flying time (fig. 1). understand the following: RNP The most powerful feature of the ICAO 1. RNP as initially conceived RNP concept is the specification of a Actual airplane location within 10 nmi RNP by the International Civil minimum performance requirement with- 10 nmi Aviation Organization (ICAO). of navigation system out equipment mandates. This is a major position at least 2. Industry expansion of improvement over the previous method Desired 95% of flight time ICAO RNP. of deriving airspace design based on path traditional discrete navigation systems (airway) 3. RNP capabilities on Boeing or on a broad population of airplane 2 x RNP airplanes. navigation systems with widely varying 10 nmi 4. Assessment of RNP capabilities. performance. However, other factors besides navigation performance (such as 5. Operational approvals. 10 nmi 10 nmi intervention capability, traffic density, RNP The aviation industry projects that increasing demands and route structure) must be considered on airspace will result in more air travel delays and in determining the route separation related costs, unless the traditional system of airplane RNP AS INITIALLY CONCEIVED reduction possible with ICAO RNP (fig. 2). 1 BY THE INTERNATIONAL CIVIL navigation, monitoring, and control is changed. In AVIATION ORGANIZATION 2 ICAO RNP AIRSPACE BUFFER REDUCTION RNP leads to reduced buffers for route spacing and response, a new tool, called required navigation per- In 1983, the ICAO formed the FIGURE increased traffic capacity in the same airspace. formance (RNP), is being developed that will be a key Future Air Navigation System (FANS) Navigation performance Committee to develop a broad strategy POPP 10 nmi element in reducing en route airplane separation and, that included new methods for airplane as a result, increase airspace capacity. This tool communication, navigation, and sur- Pre-RNP RNP defines the navigation accuracy an airplane must have veillance, and air traffic management PLMN (CNS/ATM) (see “Operator Benefits of to operate within a defined airspace. Ensured naviga- FANS” in Aero no. 2, April 1998). The navigation element of CNS/ATM centers 60 to 100 nmi tion performance and standardized functionality of Mitigates navigation errors, on the concept of RNP. RNP provides Mitigates navigation errors, RNP allow new procedures to be designed for airports 5 x RNP, 6 x RNP route structure, traffic for the specification of airspace based navigation performance, route (50 to 60 nmi) density, surveillance, ATC, where infrastructure or terrain makes it difficult or on demonstrated levels of navigation structure, traffic density, sur- communication performance and certain functional veillance, ATC, communication impossible to use some runways. RNP also allows for capabilities, rather than a required set improvements to procedures that are demanding on of navigation sensors or equipment. flight crews. Boeing has been a leader in developing Area navigation (RNAV) functionality is a key element of the RNP concept. PWVG national and international technical standards for (Area navigation systems define RNP capability, which now is available on all Boeing waypoints by latitude and longitude Legend: coordinates and allow for navigation PLWX airplanes in production and in service. on any desired flight path rather than Desired path RNP 95% threshold one defined by ground-based radio AERO AERO 28 29 Lateral containment limit. The new repeatable paths over the ground lower landing minimums, and reduced containment limit specifies an addi- 3 RNP RNAV CONTAINMENT for a given airway or procedure. Also workload, all of which contribute to 5 RNP SYSTEM SCHEMATIC tional requirement on navigation FIGURE specified in the MASPS was a real-time improved safety margins. FIGURE system uncertainty beyond the ICAO display of the estimated navigation Containment limit: 99.999% concept of 95 percent accuracy system accuracy (called “estimated RNP CAPABILITIES ON performance. The lateral (cross-track) position uncertainty” [EPU] or “actual 3 BOEING AIRPLANES dimension of this containment limit navigation performance” [ANP] on RNP RNAV functionality is available is twice the size of the RNP value and Boeing commercial airplanes). With on all Boeing commercial airplanes in RNP: 95% 2 x RNP centered on the airplane’s defined path an explicit display of EPU/ANP, the production and can be retrofitted on (fig. 3). The navigation system must flight crew can monitor trends while Boeing models delivered without ensure that the airplane remain within the navigation system automatically RNP capability. this containment region 99.999 percent checks current performance against The MASPS established all signifi- of the flight time. This outer linear Defined path required performance (i.e., the RNP cant aspects of navigation system containment region will be used to Desired path necessary for the operation). The assess the safe separation of airplanes system alerts the flight crew when performance, assurance, capability, and and obstacle clearance when develop- performance is inadequate for the functionality that must be considered ing routes, areas, and procedures. current operation. for RNP-based operations. Because many current systems will not meet RNP This industry-expanded specification Minimum navigation system every MASPS requirement, any system of RNP is called RNP RNAV to differen- capabilities. In addition to specifying deviations from the MASPS can be tiate it from the incomplete specifi- requirements for continuity and avail- mitigated through limitations or cation of RNP defined by ICAO. RNP operational procedures. This will allow ability of required positioning accuracy, Containment limit the MASPS specified capabilities to RNAV will be an aid in both separa- as many airplanes as possible to be ensure consistency of flight paths tion and collision risk assessments qualified during the transition to RNP ■ operations. The Boeing RNP RNAV and operations across the fleet. For RNP RNAV is referenced to the for proposed routes and procedures. example, the types of flight plan legs airplane defined path This will reduce route separation and designs have addressed all the key func- improve obstacle clearance limits tional and performance requirements that could make up RNP route seg- ■ ICAO RNP is referenced to the beyond those provided by ICAO RNP of the RNP MASPS. Further MASPS- ments were limited and standardized airspace desired path to ensure that all similarly equipped (fig. 4). Benefits include increased compliant changes to Boeing designs airplanes fly consistent and airspace capacity and efficiency, most likely will be warranted by operations and the evolution of RNP. Questions concerning MASPS compliance RNP 4 RNAV EXAMPLE for specific models should be directed 4 to Boeing Field Service representatives. FIGURE RNP RNAV is a tool to facilitate further optimization appropriate area on the crew alerting certification and limitations approved (reduction) in airspace buffers. Boeing RNP functionality includes message display. Other airplanes by the FAA and other regulatory flight crew interface through a flight (such as the 737 and MD-80) display authorities. The AFMs for Boeing management control display unit 4 nmi 8 nmi the message on the