GM1 ACNS.C.PBN.101 Applicability

ED Decision 2019/011/R

Subpart C of CS-ACNS provides certification criteria for performance-based navigation. EASA has considered the current and future aircraft equipment and has assumed that most, if not all, aircraft are equipped with one or more GNSS receivers. Subpart C, therefore, considers GNSS equipped aircraft and focuses on compliance with RNP navigation specifications. Compliance with Subsection 2, however, also assures compliance with the RNAV 10, RNAV 5, RNAV 2, and RNAV 1 navigation specifications.

Where the term ‘Required’ is used in Table 1, it refers to compliance with the navigation specification.

It should be noted that for multi-sensor RNP systems, loss of RNP capability does not imply loss of RNAV capability if an inertial or DME navigation source(s) is(are) still operable.

It should be noted that this Subpart does not address communication and surveillance considerations that are, in some cases, related to the implementation of a navigation specification (e.g. controller-pilot data link communications (CPDLC) and automatic dependent surveillance — contract (ADS-C) for RNP 4) within a particular airspace.

The ICAO PBN Manual (Doc 9613) contains 11 navigation specifications, each of them addressing specific operations by flight phase:

(a)     RNAV 10, historically referred to as RNP 10, is applied for oceanic and remote continental navigation operations;

(b)     RNAV 5, RNAV 2 and RNAV 1 are applied for continental en-route and terminal navigation operations;

(c)      RNP 4 and RNP 2 and A-RNP are applied for oceanic and remote continental navigation operations;

(d)     RNP 2 and A-RNP are applied for continental en-route navigation operations;

(e)     RNP 1 and A-RNP are applied for terminal navigation operations;

(f)      A-RNP, RNP APCH, and RNP AR APCH are applied for initial, intermediate, final, and missed approach navigation operations, and may include requirements for vertical navigation (VNAV);

(g)     RNP 0.3 was specifically written to facilitate (low-level) en-route operations with rotorcraft.

Subpart C on performance-based navigation contains basic and supplemental certification criteria. The basic criteria must always be complied with, regardless of the navigation specification, and ensure compliance with the navigational requirements of the RNAV 10, RNAV 5, RNAV 2, RNAV 1, RNP 2, RNP 1 and RNP 0.3 criteria.

Some navigation specifications require compliance with supplemental criteria, e.g. compliance with Subsection 10 for parallel offsets for RNP 4.

The criteria for navigation specifications that include approach, i.e. A-RNP, RNP APCH and RNP AR, are more specific. Subsection 3 (‘LNAV in final approach’) and Subsection 5 (‘VNAV in final approach’) apply to these operations. In addition, both RNP AR and A-RNP have their own specific criteria that need to be met, as described in Subsection 6 for RNP AR and Subsection 7 for A-RNP.

Subsection 4 addresses vertical navigation (VNAV) outside the final approach part of the flight. It contains criteria for compliance with altitude constraints considered in Commission Implementing Regulation (EU) 2018/1048.

In addition to the criteria for RNP APCH approaches, Subsection 5 also contains optional requirements for advisory VNAV, which apply to the final approach segment (FAS) only.

Subsections 8, 9, and 10 contain criteria for specific functions. These functions (radius to fix, fixed radius transition, and parallel offset) are required for some applications and are optional for some others.

In some instances, the CS requirements deviate from the ICAO navigation specification, for example by requiring VNAV for RNP APCH. This is based on recent certification experience, the fact that CS-ACNS is a forward-looking document that is based on the latest ICAO and industry standards, and it is also a consequence of the way Section 1 has been structured. Where applicants intent to strictly apply the criteria of the ICAO navigation specification, they are invited to consult EASA (e.g. an applicant applying for RNP APCH without VNAV down to LNAV minima or LP minima only).

Applicants intending to apply strictly for RNAV navigation specifications predicated on conventional ground navigation aids, i.e. non-GNSS-based navigation, are also invited to consult EASA.

Example application of Table 1:

Question: An applicant wishes to apply for certification of an aircraft for RNP APCH. Which subsections of Subpart C should the applicant demonstrate compliance with?

Answer: Subsections 1 and 2, and the supplemental and the more stringent criteria provided in Subsections 3 and 5 for lateral and vertical navigation, respectively. The applicant may need to also demonstrate compliance with Subsection 8, which is optional, as the RF functionality could be used in the initial and intermediate approach segments, and in the final phase of the missed approach.

Additionally, Appendix C to Subpart C provides guidance material for the installation of equipment constituting the aircraft’s RNP system and for testing the aircraft’s RNP system.

[Issue: CS-ACNS/2]