Annex D: Additional Technical Considerations

1. General

1.1 This annex identifies additional technical considerations and criteria provided by the TAA to supplement those selected from AC 20 138D (reference 3.2.2.a). Not all of these considerations may be applicable to a specific design approval.

2. Rationale and Guidance

2.1 The following additional technical considerations apply to the certification of a PBN design:

1. Containment. If the PBN capability is being added to an existing avionics design, the Design Assessment Report developed in Step 4 should review the prior certification records for the design, including:
   1. existing exemptions and deviations;
   2. service history;
   3. operating procedures; and
   4. existing Flight Manual/Aircraft Operating Instructions (FM/AOI) limitations and capability statements.
2. Unique Designs. The aircraft may have navigation capabilities for which there are no navigation performance criteria in AC 20-138D, such as inertial coasting. As a minimum, the performance of these navigation capabilities must be substantiated and addressed by the containment continuity and containment integrity analysis, or limitations applied when appropriate.
3. Baro VNAV to High-Elevation Aerodromes. Baro VNAV capability statements that are based on the criteria of AC 20-138B or AC 20-129 (reference 3.2.2.j) must have an AFM limitation prohibiting Baro VNAV Approach procedures to airfields above 6,000 feet MSL. This is consistent with EASA Safety Information Bulletin (SIB) 2014 04, ‘RNP Approach with Baro-VNAV’ (reference 3.2.2.i). The EASA SIB accepts certification to FAA AC 20-129 for European operational approval up to a field elevation of 6,000 feet MSL. Section 7 of EASA Certification Memo (CM) AS 002 Issue: 02, dated 28 March 2014 (reference 3.2.2.k), discusses the matter in detail and suggests operational mitigations.
4. Inoperative Equipment. The effect of inoperative equipment on the PBN capability must be assessed and, if necessary, addressed by the FM/AOI limitations, or the Master Minimum Equipment List (MMEL).
5. Aircraft-based Augmentation. AC 20-138D, paragraph 15-6 b identifies the requirement for a performance limitation in the AFM when equipment uses an aircraft-based augmentation system, such as Receiver Autonomous Integrity Monitoring (RAIM) (e.g., TSO C129a and C196 GNSS equipment). The limitation is to have other navigation equipment available, which is appropriate to the operation, including selecting an alternate airport. In addition, this FM limitation must address the current expectations of AIP Canada (ICAO) ENR 4.3 and RCAF Flight Operations Manual.
6. Pre-Flight RAIM Prediction Software. When required for the intended operations, RAIM prediction software and user manual used to predict GPS RAIM and Fault Detection and Exclusion (FDE) coverage for the route to be flown must be assessed and identified in the FM/AOI. Criteria are provided in AC 20-138D 5-2.3.
7. Adverse Effects of Mission Equipment or Stores. The effect of military equipment on the PBN capability must be assessed, or equipment operation restricted. Consideration should be given to external stores, display of tactical data and formats, intercom modes and transmitter operation.
8. Magnetic Variation (MagVar) Data. AC 20-138D, Change 2, paragraph 12-9.b specifies that any operating limitations must be identified and documented for installed avionics systems associated with the application of magnetic variation data (e.g., operations using magnetic heading references may only be valid between 82° north latitude and 82° south latitude) to ensure that accurate magnetic heading references are presented and used in the aircraft. Continuing airworthiness requirements should be defined to identify the need to update the magnetic variation database and, if applicable, conversion algorithms or hardware, when periodic updates become available. This requirement should also define the maintenance procedures necessary to update the on-board magnetic variation database for installed avionics systems.