5.1 Surveillance systems contribute to aircraft safe separation and support the provision of safe and effective air traffic control services. Aircraft avoidance systems provide warnings and alerts to aircrew of impending hazards associated with proximity to other air traffic or terrain.
5.2 While Defence aircraft without surveillance and avoidance systems would not normally be precluded from operations in civil airspace, sub-optimal routes and timings may be imposed. Therefore, fitment of surveillance and avoidance systems in Defence aircraft is, ultimately, a capability and safety decision for the capability manager.
5.3 When operating in civil airspace, Defence aircraft may present a hazard to civil aircraft if the Defence aircraft does not provide the same surveillance and avoidance systems capabilities as those required by civil NAAs for civil aircraft operations. The civil NAA standards for surveillance and avoidance systems usually provide an appropriate benchmark for surveillance and avoidance systems performance and ensure appropriate interoperability with civil aircraft in civil airspace. Military Airworthiness Codes may not prescribe standards for surveillance and avoidance systems, and civil Codes may prescribe different standards for similar operations in civil airspace. Finally, where Defence operations only present a hazard to the Defence aircraft (rather than a third party risk to other airspace users), and/or where the concept of operations for the Defence aircraft differs from that in civil aircraft (for example Terrain Awareness and Warning Systems (TAWS)), applying the civil standards to Defence aircraft may not be useful or warranted. Consequently, the Authority prescribes airworthiness design requirements for Defence aircraft surveillance and avoidance systems.
5.4 This Chapter prescribes Authority supplementation to the aircraft surveillance and avoidance systems elements of recognised civil and military Airworthiness Codes. Importantly, the airworthiness design requirements in this chapter are not suitable for application in isolation from an Airworthiness Code. The Authority’s requirements for the application of recognised Airworthiness Codes are defined in Section 1 of the DASDRM.
5.5 This section presents the Authority prescribed airworthiness design requirements for Defence aircraft surveillance systems.
5.6 ATC transponders provide responses to interrogations from ground based secondary surveillance radar, to support aircraft safe separation and may be used by other aircraft to support traffic collision avoidance. ATC transponder equipment is mandated for all civil aircraft operating in certain classes of civil airspace. Some civil NAAs are mandating retrospective fitment of ATC transponder equipment with functionality that exceeds the ‘basic’ aircraft identification and altitude data traditionally provided by ATC transponders (eg CASA requires all aircraft operating in Australian airspace to be fitted with a Mode S transponder in specified locations and classes of airspace).
5.7 Design Requirement (Essential). Where a Defence aircraft requires unimpeded access to civil airspace in which the fitment and operation of an ATC transponder is mandated for civil aircraft, the Defence aircraft transponder must satisfy the requirements prescribed by the relevant civil NAA, as follows:
for operations in Australian airspace, CASR Part 91 Manual of Standards
for operations in US airspace, FAA FAR 91.215, ATC transponder and altitude reporting equipment and use
for operations in European airspace, EASA Certification Specifications and Acceptable Means of Compliance for Airborne Communications, Navigation and Surveillance (CS-ACNS) Book 1 Subpart D Section 1, 2 or 3 as applicable.
5.8 While lack of an ATC transponder may not preclude access to civil airspace, such access may be severely limited since the transponder affords air traffic controllers the situational awareness necessary to provide separation advice and control to airspace users, and provides other airspace users with traffic collision avoidance advice and commands in congested airspace. An ATC transponder that does not comply with the associated civil airworthiness design requirements may not provide the required performance or functionality to support air traffic control services and traffic collision avoidance, and may therefore pose a hazard to other airspace users.
5.9 Automatic Dependent Surveillance – Broadcast (ADS-B) provides ‘radar-like’ air traffic information to support civil aviation operations in Australia, the United States and Europe. ADS-B provides transmission and reception of broadcast messages, which detail an aircraft’s position (latitude and longitude), altitude, velocity, aircraft identification and other parameters. Civil NAAs have implemented a program of prescribing ADS-B fitment to civil aircraft operating in specified classes of airspace. For example, CASA has mandated ADS-B compliance for all civil aircraft operating under Instrument Flight Rules or above FL 290 in Australian airspace.
5.10 Design Requirement (Essential). Where a Defence aircraft requires unimpeded access to ADS-B designated airspace, the equipment must satisfy the requirements prescribed by the relevant civil NAA, as follows:
for operations in Australian airspace, CASA AC 21-45v2.2 Airworthiness Approval of Airborne Automatic Dependent Surveillance Broadcast Equipment
for operations in US airspace, FAA AC 20-165B Airworthiness Approval of ADS-B Out Systems, for a 1090 MHz Extended Squitter system
for operations in European airspace, EASA Certification Specifications and Acceptable Means of Compliance for Airborne Communications, Navigation and Surveillance (CS-ACNS) Book 1 Subpart D Section 4 – 1090 MHz Extended Squitter ADS-B.
5.11 ADS-B equipment fitted to Defence aircraft must satisfy the ADS-B design requirements prescribed by the relevant NAA for operations in designated ADS-B airspace. Non-compliance with these requirements could pose a hazard to other airspace users if the equipment fails to accurately report the Defence aircraft’s flight data, or incorrectly receives and / or interprets other aircraft data.
NOTE
The minimum data messages required for US and European ADS-B operations may not be achieved by ADS-B equipment that complies with the CASA requirements. While ADS B equipment compliant with CASA’s airworthiness requirements may be technically capable of broadcasting all FAA and EASA mandatory data messages, the equipment may not be configured to do so, since some of the mandatory system status messages are not required by CASA. Therefore, where Defence aircraft ADS-B operations in US or European airspace are required, the minimum broadcast capabilities of Defence equipment must be verified to comply with the relevant FAA and / or EASA requirements.
5.12 Continuing airworthiness requirement. ATC transponder serviceability testing should be conducted at least every two years, per the requirements detailed in FAA Part 43 Appendix F.
5.13 ATC transponder systems require periodic testing to confirm that the system continues to generate data that meets the civil benchmark standards and can be safely used by air traffic controllers to manage associated airspace.
5.14 This section presents the Authority prescribed airworthiness design requirements for Defence aircraft avoidance systems.
5.15 The Traffic Alert and Collision Avoidance System (TCAS) monitors the traffic situation around an aircraft and provides information on the approximate bearing and altitude of other aircraft, generates collision warnings to the pilot that another aircraft is in near vicinity (Traffic Advisories (TA)) and provides suggested avoidance actions (Resolution Advisories (RA)). While civil NAAs prescribe fitment of TCAS in large passenger carrying aircraft operating in certain classes of airspace and operations, there is no consistent application of a TCAS mandate. The lack of TCAS on Defence aircraft does not preclude or limit access to civil airspace. Nevertheless, TCAS provides a safety benefit that may be warranted for Defence aircraft operations in civil airspace (or for unique military operations where aircraft are in close proximity) and a determination should be sought from the capability manager regarding the requirement for TCAS.
5.16 Only TCAS II Version 7.0/7.1 systems comply with ICAO TCAS II requirements. Where civil NAAs do prescribe TCAS fitment, the TCAS II Version 7.0/7.1 requirements are levied. Therefore, the Authority has adopted the associated civil airworthiness design requirements as the benchmark for Defence aircraft TCAS.
5.17 Design Requirement (Essential). Where TCAS is fitted in a Defence aircraft, the equipment must comply with the requirements prescribed in FAA AC 20-151C Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) Versions 7.0 & 7.1 and Associated Mode S Transponders.
5.18 TCAS equipped aircraft conduct coordinated responses to potential conflicts to avoid mid-air collisions. A Defence aircraft fitted with a non-compliant TCAS may respond to a RA generated by another TCAS equipped aircraft in an uncoordinated manner, which may lead to mid-air collision. Consequently, where TCAS capability is confirmed to be required for Defence aircraft operations, the TCAS system must comply with the civil requirements to ensure compatibility with other airspace users.
5.19 Terrain Awareness and Warning Systems (TAWS), also known as Ground Proximity Warning Systems, provide aircrew with both aural and visual alerts to reduce controlled flight into terrain (CFIT). Civil NAAs have prescribed TAWS fitment for certain types of aircraft and operations. While some NAAs require aircraft to have TAWS, unlike other systems described in this Chapter, the lack of TAWS capability does not pose any third party risk. The decision to fit TAWS is therefore a capability decision based on the additional safety benefit provided during Defence aircraft operations.
5.20 Design Requirement (Essential). Authority advice must be sought to define airworthiness design requirements for TAWS fitted to Defence aircraft.
5.21 Circa 2021, military NAAs have not prescribed airworthiness design requirements for TAWS. Further, military aircraft often require TAWS functions and performance to provide terrain avoidance advice and commands in a ‘tactical’ environment that is not normally associated with civil operations.
5.22 Given the lack of military TAWS standards, the Authority has not established design requirements based on a specific civil or military standard and, instead, has adopted an approach of establishing design requirements on a case by case basis. Nevertheless, noting that the civil standards for TAWS support safe civil aircraft operations in close proximity to terrain, the civil TAWS requirements provide an appropriate safety benchmark. Consequently, TAWS compliance with the following civil requirements is likely to ensure safe TAWS operation in Defence aircraft provided that the CRE remains substantially similar to that for which the TAWS was originally certified:
FAA AC 25-23 Airworthiness Criteria for the Installation Approval of a Terrain Awareness and Warning System (TAWS) for Part 25 Airplanes,
FAA AC 23-18 Installation of Terrain Awareness and Warning System (TAWS) Approved for Part 23 Airplanes,
EASA CS-ACNS Book 1 Subpart E Section 1 – Terrain Awareness and Warning System (TAWS), or
FAA TSO-C194/EASA ETSO-C194 Helicopter Terrain Awareness and Warning System (HTAWS).
5.23 When prescribing design requirements for TAWS, the Authority will adopt a systems approach. TAWS rely on the integrity of: the terrain data, the aircraft navigation systems that establish where the aircraft is in relation to terrain obstacles, and the TAWS processing hardware and algorithms. The civil standards identified above utilise this ‘systems’ approach to prescribing TAWS requirements; however, they may not cater for the intended TAWS operational use in a Defence aircraft. Failure to install TAWS equipment and associated data that satisfies appropriate performance and design assurance requirements could contribute to CFIT. Consequently, the Authority will confirm airworthiness design requirements for TAWS in Defence aircraft on a case-by-case basis to ensure that appropriate TAWS requirements are defined for the proposed aircraft operations.
5.24 This section presents design requirements that are not prescribed by the Authority, but identify particular capability and interoperability design considerations for establishing requirements for Defence aircraft surveillance systems.
5.25 IFF systems ensure that Defence aircraft in national and international operations are not identified by other coalition assets as ‘hostile’. IFF systems that are not compliant with a design standard prescribed by coalition partners may prevent Defence aircraft from being correctly identified during operations. Where an IFF system is necessary to satisfy capability requirements, Defence requires Mark XIIA IFF systems to be fitted to Defence aircraft.
5.26 Capability Requirement. IFF systems fitted to Defence aircraft should be certified to the US DoD AIMS (Air Traffic Control Radio Beacon System, Identification Friend or Foe, Mark XII/XIIA System) 03-1000B Amendment 2.
5.27 Mark XIIA IFF systems provide the performance, security and encryption capacity required for interoperability with ADF European and US coalition partners. Per the Mode 5 IFF Capability Realisation Plan, only IFF MK XIIA systems that meet the requirements in the current version of the US DoD AIMS standards are acceptable for Defence aircraft IFF operations, including Mode 5 Level 1 and Level 2 operations.
5.28 Further guidance on implementing the surveillance and avoidance systems requirements prescribed in this chapter can be provided by the chapter sponsor.