Annex D: Additional Technical Considerations and Interpretations

1. General

1.1 This annex identifies additional technical considerations and criteria provided by the TAA to supplement those found in the various TCCA, FAA and EASA advisory materials. Not all of these considerations may be applicable to a specific design approval.

2. Rationale and Guidance

2.1 ADS-B Out

2.1.1 Continuity

2.1.1.1 The EASA continuity (loss of function) requirement for ADS-B Out functionality is defined in CS-ACNS Issue 4 (advisory reference 3.2.2.g) Section – “AMC1 ACNS.D.ADSB.105 Continuity”, as 2x10^-4 /flight hour.

2.1.1.2 The FAA requirement for continuity considers the loss of function of an ADS-B Out system to be a Minor failure condition, which equates to a continuity of 10^-3/flight hour (advisory reference 3.2.2.m, Para 3.b.).

2.1.1.3 Therefore, the TAA’s recommended ADS-B Out functionality continuity requirement is dependent on whether operations will be conducted within the USA or Europe. For aircraft where the Statement of Operating Intent (SOI) clearly indicates that operations will only ever occur within the USA, a continuity requirement of 10^-3/flight hour is applicable. For aircraft where the SOI indicates operations will also occur in Europe, a continuity requirement of 2x10^-4/flight hour is applicable. Either requirement can normally be achieved by a single ADS-B Out system.

Note: Although technical airworthiness criteria for continuity could be met with a single ADS-B Out system, the operational community will have to consider whether a single system is sufficient to support their dispatch reliability requirements.

2.1.2 Antenna Diversity

2.1.2.1 FAA AC 20-165B (advisory reference 3.2.2.k) allows a single bottom-mounted antenna, under certain conditions, for ADS-B Out. The EU CS-ACNS (advisory reference 3.2.2.g) section – “CS ACNS.D.ADSB.040” specifies which aircraft must implement antenna diversity for ADS-B Out or Mode S. TCCA has mandated the use of space-based ADS-B which is implemented through a partnership with Aireon on the Iridium satellites constellation. Although antenna diversity is not a formal TCCA requirement, it is likely that antenna diversity will be required for most installations.

2.1.2.2 Having antenna diversity on an aircraft improves the ability of the ground-based system to continue tracking the aircraft, especially during aircraft maneuvers. Antenna diversity becomes a necessity for operations in airspace monitored by a space-based ADS-B Out system. Therefore, it is recommended that Applicants implement an ADS-B Out design that includes antenna diversity.

2.1.3 Position Source

2.1.3.1 The civil regulations for ADS-B Out require that the position source meet strict performance requirements. FAA AC 20-165B (advisory reference 3.2.2.k), para 3.3 recommends a method by which this can be accomplished.

2.1.4 Flight Test

2.1.4.1The FAA-based ADS-B Out system utilizes a ground-based surveillance infrastructure. The Canadian ADS-B Out infrastructure utilizes a space-based surveillance infrastructure. Since the two are fundamentally different, it is required that, during the flight test program, the ADS-B Out performance be verified with both ground and space infrastructure, if a fleet intends to operate in Canada and the U.S. This can be accomplished by obtaining both a FAA Public ADS-B Performance Report (PAPR) and a NAV CANADA Detailed ADS-B Performance Report (DAPR), as identified below.

2.1.4.2 FAA AC 20-165B provides guidance for the installation and airworthiness approval of ADS-B Out systems in aircraft, including the flight test requirements. The flight test is expected to generate a PAPR. The Public ADS-B Performance Report User’s Guide can be found at https://adsbperformance.faa.gov/PAPRUsersGuide.pdf. The User’s Guide describes the parameters collected and reported in the PAPR, which is generated by the FAA upon request. 

2.1.4.3 A NAV CANADA DAPR is available upon request as identified in TCCA AC 500-029 Issue 2.

2.1.4.4 CS-ACNS Issue 4 (advisory reference 3.2.2.g) does not mandate a flight test for the European airspace.

2.1.5 Position Source and Transponder Previously Approved Pairing

2.1.5.1 Pairing of position source and transponder from an FAA previously approved implementation can be found on the FAA website.

2.1.5.2 Using previously approved pairing data can make compliance substantiation simpler. Should there be any deviations from the previously approved pairing, the Applicant must analyze and account for those deviations.

2.1.6 Latency

2.1.6.1 There is a time requirement between the actual position reading and the publishing of the position. This is called latency. If the installation has already been approved under 2.1.5.1 and the installation is the same, the latency requirement is considered satisfied. If a latency calculation must be performed, the calculation shall be as described in Appendix C of FAA AC 20-165B.

2.1.7 Master Minimum Equipment List (MMEL)

2.1.7.1 If an aircraft has a MEL or a MMEL, the installation of the surveillance system may impact it. The MEL or MMEL must be reviewed during the design change process and any required amendments must be submitted to TAA and OAA for approval.

2.1.8 Aircraft certification with ADS-B out before TCCA AC 500-029 Issue 2

2.1.8.1 TCCA AC 500-029 Issue 2 (advisory reference 3.2.2.o) paragraph 4.1 General Notes item (7) states that:

2.1.8.2 As such, fleets already certified with documented compliance against both FAA and EASA identified means of compliance may amend their AFM surveillance capability statement per Annex H to document their eligibility to conduct ADS-B Out operations in Canada.

2.2 ADS-B In

2.2.1 There is currently no airspace where ADS-B In equipage is mandated. Its purpose is to provide more situational awareness to the operators. If integrated with existing ACAS/TCAS or Traffic Avoidance System (TAS) displays, the Applicant will need to show that the ACAS/TCAS/TAS installation has not been compromised through an appropriate system safety assessment.

2.2.2 FAA AC 20-172B (advisory reference 3.2.2.l) provides guidance for the initial installation and airworthiness approval of ADS-B In equipment in aircraft for each of the applications chosen.

2.3 Military IFF Mode 5

2.3.1 Mode 1, 2 and 3 are implicitly included in Mode 5 Level 1 or Level 2 systems and, therefore, included in the discussion herein. Mode 4 was decommissioned in June 2020.

2.3.2 The IFF Mode 5 functionality is considered by the TAA as miscellaneous non-required equipment (see advisory reference 3.2.2.f). However, IFF Mode 5 capable Line Replaceable Units (LRUs) often contain Mode A/C, Mode S and ADS-B Out capabilities. Therefore:

1. the civil functionalities integrated within the IFF must be approved in accordance with the civil criteria contained in this TAA advisory; and
2. IFF equipment and installations which meet the requirements of AIMS 03‑1000B Amdt 1 (advisory reference 3.2.2.b) or STANAG 4193 Edition 3 (advisory reference 3.2.2.c) include non-interference testing against civil functionalities. Those test results can be used to substantiate the non-interference requirements defined in TAA Advisory 2006-04 (advisory reference 3.2.2.f).

Note: AIMS 03-1000B Amdt 1 applies to IFF Mode 5 and the civil surveillance requirements. It includes the requirements from STANAG 4193. Since it is expected that Canadian military fleets will be operating in U.S. airspace and using U.S. crypto keys, it is recommended that AIMS 03-1000B Amdt 1 be used.

2.3.3 In order to use National Security Agency (NSA) cryptography (crypto) keys and operate IFF equipment in U.S. airspace, a “Letter of Certification” from the DoD AIMS is required (DSCA Policy 11-40). The DoD AIMS certification is comprised of the transponder certification and the platform certification. It includes qualification of the military and civil surveillance functionalities. The system must meet AIMS 03‑1000A Amdt 1 or STANAG 4193 Edition 3. DoD AIMS will provide the Applicant with a Letter of Certification stating the exact configuration that the certification was performed against. The Letter of Certification is not an airworthiness certification, but rather a “Fit for Use” confirmation that the transponder and the platform provides the intended military functionality.

Note: DoD AIMS certification requirements are not a replacement certification standard for Mode A, C, S and ADS-B requirements. However, the Applicant is encouraged to leverage required AIMS testing artifacts (ground test report, flight test report, etc.) to demonstrate compliance with the aircraft certification basis when possible and arranged with the Finding Authority. Mode S and ADS-B are covered in the AIMS Certification and Operational Requirements AIMS 03‑1000B Amdt 1 or STANAG 4193 Edition 3, only to the extent that military requirements may differ from the requirements of non-government documents. Furthermore, the DoD AIMS Letter of Certification does not cover certification items such as System Safety, Structural, Load Analysis, Human factors, etc.

2.3.4 The military IFF capability includes classified requirements. These classified requirements do not impact the technical airworthiness certification of military or civil surveillance systems, but will require qualification by DoD AIMS.

Note: If the Applicant intends to have one civil surveillance system and one military IFF system, not integrated within one LRU, it is recommended that they discuss it with DTAES 6 before committing to the design.

2.3.5 Position Source

2.3.5.1 Military IFF Mode 5 Level 2 requires a GPS source with P(Y) or M code capability.

3. Other Considerations

3.1 Aircraft Level System Safety Considerations

3.1.1 The content of this TAA advisory is primarily directed at the installation and certification aspects of surveillance systems. These systems might be installed as a stand-alone item, or installed as part of a more substantial avionics upgrade program. The avionics upgrade will likely also include changes to civil communication and/or navigation capabilities. Prior avionic upgrade program experience has identified the lack of clear guidance surrounding required probability failure levels. This has resulted in numerous discussions with respect to the required probability failure levels that would be appropriate to Communication, Navigation and Surveillance Systems (CNS), that are intended to be used to fulfill civil Air Traffic Management (ATM) functions.

3.1.2 Canadian Forces Technical Order A-GA-005-000/AG-001 – The Department of National Defence/Canadian Armed Forces Airworthiness Program, 2020 (regulatory reference 3.2.1.c), Part 2 – Airworthiness Requirements, Section 1, identifies the following Airworthiness Safety Criteria applicable to the DND/CAF:

1. the DND responsibility to operate all DND-Registered Aircraft with due regard for the safety of other air traffic. This requires DND aircraft to be equipped and certified to meet the CNS/ATM performance requirements; and
2. the Baseline Safety Criteria applicable to various classes of DND aircraft which allows for relaxation of the required quantitative probability of failure criteria for certain classes of aircraft.

3.1.3 For CNS/ATM capabilities, the TAA expects that civil standards will be used. Therefore, the relaxation of the quantitative failure criteria for Military Aircraft General (Fixed-Wing Transport Aircraft and Helicopters) and Military Fighter and Trainer Aircraft (Ejection Seat Equipped) identified in Figure 2-1-1 (regulatory reference 3.2.1.c) is not considered appropriate for equipment and installations providing civil CNS/ATM capabilities.

3.2 ICAO 24-Bit Aircraft Address Codes

3.2.1 If ICAO 24-bit aircraft address codes have not already been assigned to a RCAF fleet, the WSM or PMO can contact DAR 3 as the DND OPI for such codes.

3.3 Radio Licensing and Interrogator Use Agreements

3.3.1 Any RCAF radio equipment, such as IFF transponders and interrogators, must be licensed by Assistant Deputy Minister (ADM) Information Management (IM)/Director General Information Management Operations (DGIMO)/DND Frequency Spectrum Management (DFSM) as complying with the Canadian Radio Communications Act.

3.3.2 The Applicant should direct frequency spectrum management enquiries to ADM(IM) DFSM. DFSM policy, direction and contact information can be found internally, within DND, at: http://admim-smagi.mil.ca/en/it-services/radio-spectrum-space/spectrum.page.

3.3.3 ADM(IM)/DFSM publishes policy, standards for spectrum management and instructions for obtaining spectrum supportability, licencing and frequency assignments for DND/CAF radio-frequency emitters in CFTO B-GT-D35-001/AG-000 (advisory reference 3.2.2.n). This publication is also referred to as DNDP35, and is available internally, within DND, at: http://admim-smagi.mil.ca/en/it-services/radio-spectrum-space/spectrum-management/dndp-35.page.

3.4 IFF Mode 5 National Origin Code and Platform Identification Number

3.4.1 IFF Mode 5 requires a National Origin (NO) code and a Platform Identification Number (PIN). DAR 3 is the OPI for the NO codes and PINs.

3.4.2 The NATO National Origin codes effective 2019 are listed in (advisory reference 3.2.2.a).

3.4.3 Since the allocated NO codes and PINs can change over time, it is, recommended that the WSM/PMO contact DAR 3 to obtain the current NO codes and PINs.