Proposed amendment to Part 172 Manual of Standards - Provision for visual surveillance systems for aerodrome control services (CD 2203AS)

We sought industry feedback over the period 26 September – 24 October 2022 on proposed changes to air traffic services (ATS) facility and equipment standards. This was detailed in Chapter 3 of the Part 172 Manual of Standards (MOS).

The proposed changes included:

• enabling use of electro-optical technology (known as visual surveillance system (VSS)) in the provision of aerodrome control services
• addressing a gap in the control tower sight line requirements for situations at an aerodrome with an existing aerodrome control facility where a new runway is commissioned, or an existing runway is modified
• removing standards from the Part 172 MOS that replicate standards already specified by the International Civil Aviation Organization (ICAO).

About this consultation
This consultation occurred to address outcomes of a post implementation review (PIR) of the regulations and standards that apply to ATS providers. The PIR revealed that the existing regulatory arrangements for facilities and equipment were at the same time restrictive and inadequate for dealing with new installations at aerodromes. There was also considerable and unnecessary replication with equivalent ICAO standards and recommended practices.

We received 6 responses. One from an ATS provider, 2 from air traffic controllers, 2 from pilots, and 1 from a CASA staff member. Four respondents consented to having their comments published and 2 requested their submissions be kept confidential.

Summary of feedback
Four respondents agreed with the proposal to enable the use of VSS; however, 2 of those responses sought or recommended changes to certain requirements or the wording of the standards.

Two respondents disagreed with the VSS proposal with 1 saying the existing standards are not restrictive and that more regulatory standards are not required. The other respondent submitted a detailed statement challenging the concept of indirect human observation for ATS and the apparent contradiction between this concept and ATS provider assurances that controllers will always be locally based and highlighting the vulnerability of the interconnecting data links.

Three respondents agreed with the proposal to extend the performance requirements for newer control towers to apply to new or modified runways. One of those respondents said there were several aerodromes potentially impacted by the performance requirement and that it would take time to develop and implement a solution. The respondent requested a 24-month horizon for implementation.

One response was 'Undecided/Not my area of expertise' about the proposed performance requirements and 1 respondent did not provide an answer to the question. On the other hand, 1 respondent did not agree with the proposal saying it may be difficult to construct a new runway so that it cost-effectively meets the proposed movement from an existing control tower.

Four respondents agreed with the proposal to delete standards in the Part 172 MOS that replicate existing ICAO standards. One response was 'Undecided/Not my area of expertise' and 1 respondent did not provide an answer to the question.

Three respondents agreed with the proposal to extend the range of ICAO standards that would apply for the purposes of Division 172.C.3 of the Civil Aviation Safety Regulations 1998 (Standards for facilities and equipment). One response was 'Undecided/Not my area of expertise' and 1 respondent did not provide an answer to the question. On the other hand, 1 respondent did not agree with the proposal explaining that there may be insufficient equipment screen space to display all the data that would need to be supplied to an aerodrome control service unit, and that:

 "…there may be a disconnect between Met provider and ATS provider obligations with the increased reliance on ICAO recommendations and requirements".

In 'additional comments' to the consultation, 1 respondent said removing people by the introduction of remote ATS operations would degrade local situational awareness and local knowledge. Another respondent said that applying the detailed visibility in 3.03 (1) and (2) to existing control towers would likely result in retrospective non-compliance for established control towers and that this would necessitate a transition period to allow remedial action. The respondent also made the following comments or requests:

• The draft paragraph 3.03 (c) (visibility of service roads) is broader in scope than the existing requirement and is not required by ICAO Annex 11.
  • The respondent suggested the requirement should apply to service roads that are within 150m of a runway strip - that is subparagraph (b) but not the more generic (a) - manoeuvring area.
• Confirmation that VSS can be used for applying standards within the broad scope of the ICAO Procedures for Air Navigation Services - Air Traffic Management (ICAO Doc 4444) (beyond Chapter 7).
• The signal lamp requirement should cater for situations where the control tower unit is remote from the aerodrome.
• Control towers should not be required to display information about space weather.
• Tower controllers should always have visibility of the local airborne operations, whether nor not the tower has dedicated airspace.
• ATC units should not have to monitor area navigation systems or the backup navigation network.

Next steps
We appreciate all the comments provided by the respondents to this consultation.

Regarding the comment of 1 respondent that the term control tower does not imply a physical building, we have advice that the standards in Chapter 3 of the Part 172 MOS can be interpreted as requiring a physical structure. The existence of different understanding on the matter is evidence of a need to give clear interpretation and thus overcome the potential for future argument. Accordingly, we intend to proceed with providing this interpretation.

Concerning the comment about retrospective impact of the proposed standards on existing control towers, we are of the view that section 3.03 is less onerous than existing standards rather than a new or additional obligation. The existing standard in subparagraph 3.1.2.2 (b) of the Part 172 MOS requires control towers to have 'unobstructed views', whereas the new standard narrows that requirement to focus on the certain parts of an aerodrome and surrounding airspace known to be critical for the provision of aerodrome control services. It removes any implication that additional views beyond critical areas are required. Accordingly, we intend to proceed with the proposal.

We acknowledge that the wording in subparagraph 3.03 (1)(c) exceeds the existing service road visibility standard. However, we do not believe the issue would be resolved by making the requirement apply only to service roads within 150 m of the edges of runway strips (as proposed by the respondent). A runway strip extends laterally to a distance of up to 150 m from the runway centreline, so applying the requirement to the edge of a strip potentially requires visibility of service roads as far as 300 m from the runway centreline. This is more than the current requirement. To resolve the matter, we intend to make subparagraph 3.03 (1)(c) apply for services roads within 150 m of a runway itself and not its associated runway strip. The combination of this requirement and the new requirement for visibility of runway strips (subparagraph 3.03 (1)(b)) would provide ATC with sufficient and equivalent visibility of activities occurring in the vicinity of runways—both on service roads and off those roads.

We also accept the respondent's recommendation about subparagraph 3.03(1)(e) - Visibility of surrounding airspace - and will amend the relevant clause to generally require visibility of flight operations on or in the vicinity of the aerodrome.

We confirm that VSS is useable to relevantly apply any standard within the broad scope of ICAO Doc 4444. This is implied through the broad scope of tower functions in section 7.1 of ICAO Doc 4444, for example: paragraph 7.1.1.1, which says,

 'Aerodrome control towers shall issue information and clearances to aircraft under their control to achieve a safe, orderly and expeditious flow of air traffic … with the object of preventing collision(s) between: a) aircraft …'. 'Preventing collisions'

Preventing collisions logically includes the application of separation minima and procedures, which are specified in other chapters of ICAO Doc 4444.

Regarding the comments about signal lamp requirements, displaying space weather and monitoring area navigation systems, we will amend the signal lamp requirement to accommodate remote siting of the control tower. We note the request to exclude 'space weather' from the requirement in subparagraph 3.06 (1) (c) - 'other significant weather information' of the draft instrument, but we do not agree it is necessary or appropriate to specifically exclude the information. On the one hand, the provision does not imply a specific requirement for space weather information. On the other hand, space weather information may be useful to ATS and airspace users for service provision and operation. For example, planning for a likely GNSS outage due to solar conditions. We consider that the requirement is sufficiently generic to cover a multitude of situations and types of weather information. We are also of the view that ATC has a definite need to monitor the status of navigation systems (despite the recommendation of the respondent). The proposal was for ATC to be able to monitor those navigation aids being used for control purposes and not every navigation aid in an area. We believe it is important for ATC to be aware whether a navigation aid is usable for control purposes and, therefore we, will retain the requirement as proposed.

We acknowledge the request from a respondent for a 24-month timeframe for implementing the sighting performance standards and are aware of the aerodromes potentially impacted. Accordingly, we will amend the sighting performance standards to include the requested implementation timeframe.

In relation to the respondent's concerns about remote provision of aerodrome control services or the use of VSS, we disagree that overseas experience is not translatable to the Australian situation. Remote provision of services does not automatically imply vast distances between sensors and controllers. ATS using VSS can be implemented in several ways, including:

• On-site: A conventional control tower with VSS equipment to cover blind spots.
• On-site: A control room at ground level at the aerodrome with sensor equipment installed around the aerodrome.
• Locally: A control room/display system at one aerodrome with sensor equipment at another aerodrome in close proximity. For example, situations like Hobart and Cambridge.
• Regionally: A control room/display system display at one aerodrome with sensor equipment at a different aerodrome in the near region. For example, situations like Gold Coast and Ballina.
• Between locations far apart: As described by the respondent.

Several of these examples are directly comparable with existing overseas configurations. We are aware that initial installations of VSS technology are likely to involve on-site configurations. We acknowledge that no system is invulnerable to interruption or interference. However, procedures and systems can address or overcome any potential disruption. As with any other system or process, we require an ATS provider to apply its safety management system to ensure it can safely provide air traffic services for the provision of remote services using VSS. Accordingly, we intend to proceed with VSS provisions within the Part 172 MOS.

In conclusion, we intend to proceed with changes consulted on in CD 2203AS, but with changes as discussed in this summary. We anticipate making the MOS amendments in the third quarter of 2023.