EUROCAE ED 75

Description / Abstract: The International Civil Aviation Organization (ICAO) recognized a need for dramatic improvements to the existing air navigation system. The ICAO Special Committee of Future Air Navigation Systems (FANS) developed a new concept expressed in terms of communication, navigation, surveillance and air traffic management (CNS/ATM). It was intended to be an evolutionary means of achieving improvements in the global air navigation system. To obtain the benefits of the CNS/ATM concept, aircraft need to achieve accurate, repeatable and predictable navigation performance. This is referred to as Required Navigation Performance (RNP).

The FANS concept evolved further into specific ATM modernization programs in the United States, Europe and other countries. All of these programs relied on both RNAV and RNP to enable the operational improvements needed for improved capacity, efficiency, safety, environment and global interoperability. However, the implementations led to differences in the operational applications, aircraft requirements and associated authorizations, causing confusion in the aviation community e.g. the designation of RNP 10 which through its own terms could be seen as RNAV 10.

The ICAO Performance Based Navigation (PBN) Study Group (SG) was formed after increasing misunderstanding, confusion and feedback resulted from States implementing RNAV and RNP operations in ways that differed from the original applications. The differences were significant in terms of the operational assumptions, mitigation of operational issues, management and assurance of the aircraft capabilities, etc., that could impede global interoperability and safety. The PBN SG's primary task was to create information to clarify RNAV and RNP, provide guidance to aid implementation, and harmonize and better specify area navigation and RNP, all in the development of the ICAO PBN Manual. The navigation specifications and other material in the manual are the result of the PBN SG efforts.

This document contains Minimum Aviation System Performance Standards (MASPS) for area navigation systems operating in an RNP environment. These standards are intended for designers, manufacturers, and installers of avionics equipment, service providers and users of these systems for world-wide operations. The MASPS provides guidance to aid in the development of airspace and operational procedures needed to obtain the benefits of improved navigation capability.

The requirements of this MASPS are intended to be consistent with the definitions of RNP developed by the ICAO PBN SG. The MASPS uses the term RNP RNAV for the aircraft system because it encompasses a more complete set of technical standards, definitions, considerations and requirements than is contained in any one of the individual specifications in the ICAO Manual. The MASPS represents a single, comprehensive collection of features and capabilities that can be applied in total or as a feature set tailored to specific needs e.g. as in a single PBN navigation specification, but where the features all follow the common standard established by this MASPS. In addition, barometric vertical navigation (VNAV) requirements are defined for aircraft that provide this optional capability to ensure accurate and predictable vertical paths. The VNAV requirements in this document are consistent with instrument approach procedures with vertical guidance (APV). Due to the wide disparity of climb performance of different aircraft types, this MASPS only addresses vertical path definition requirements for level flight and descent.

The MASPS contains requirements for optional functions for runway position monitoring, estimated time of arrival (ETA), and Time Of Arrival Control (TOAC). The runway position monitoring requirements apply if such a capability is included in a system developed to the MASPS. The ETA and TOAC requirements and guidance were derived from material provided by EUROCAE WG-13 and is based upon projects in the European SESAR program.

Compliance with these standards is one means of ensuring that the system and each subsystem will perform its intended function(s) satisfactorily under conditions normally encountered in aeronautical operations. The MASPS, when invoked by regulatory authorities, are expected to provide the benefits of the listed applications in section 1.3.

Section 1.0 of this document describes minimum navigation performance functions, operational goals, and applications needed to operate in RNP airspace. It also includes the assumptions made within the MASPS for defining the airborne requirements.

RNP airspace may be considered to apply to an area, route, procedure or operation using a particular RNP. The functions are described for position estimation, path definition and steering, and user interface.

Section 2.0 describes the minimum system performance requirements.

Section 3.0 describes minimum performance standards for each subsystem/function that is a required element of minimum system performance.

Section 4.0 describes an acceptable method for demonstrating system performance compliance and subsystem performance to meet the minimum standards in Section 2.0.

The appendices in the MASPS include a glossary of terms and acronyms (A), an example of system compliance analysis (B), navigation system requirements and infrastructure characteristics (C) and an example of holding pattern entries (E). Appendix F provides CNS-ATM System Considerations. Appendix G provides a table to identify where RNP RNAV, VNAV and Time of Arrival requirements exist. Appendix H is additional information supporting the recommendation for temperature compensation. Appendix I is additional guidance on the application of a MASPS RNP RNAV system in operations where the lateral navigation accuracy is less than 0.3 NM. Appendix J provides an example of a system compliance analysis for Time Of Arrival Control. Appendix K is a cross reference matrix for requirements correlation between ED-75D and RTCA DO-236C Change 1.