Explanatory Statement
Civil Aviation Safety Regulations 1998
Part 139 Manual of Standards Amendment Instrument 2025 (No. 1)
Purpose
The Part 139 (Aerodromes) Manual of Standards 2019 (the MOS) sets out the standards for the construction, maintenance and operation of certified aerodromes, and for the radiocommunications facilities required at aerodromes.
The Part 139 Manual of Standards Amendment Instrument 2025 (No. 1) (the MOS amendment) amends the MOS to incorporate the International Civil Aviation Organization’s new Aircraft Classification Rating (ACR)/Pavement Classification Rating (PCR) system (the ACR-PCR system).
The ACR-PCR system is a new international system for evaluating and reporting the bearing strengths of aerodrome surfaces or pavements (runways, taxiways, etc.) that supersedes and replaces the existing aircraft classification number/pavement classification number method of assessing such strengths(the ACN-PCN method).
Aerodrome operators are provided with a transitional period for this change. They may transition to the ACR-PCR system immediately on the 12 June 2025 commencement of the MOS amendment, or they may remain with the ACN-PCN system up until the end of 26 November 2025, beyond which point they must adopt the ACR-PCR system and report the ACR-PCR values or have their relevant aerodrome pavement published as unrated.
The 12 June 2025 instrument commencement date, and the 27 November 2025 transitional cut-off date, are pivotal because they are the Aeronautical Information, Regulation and Control (AIRAC) trigger dates for the publication of pavement values in the Aeronautical Information Publication En Route Supplement Australia (AIP ERSA).
If the aerodrome operator fails to submit the PCR value by 27 November 2025 and its pavement is published as unrated, they may correct this at a later date by means of a permanent NOTAM or through the Airservices Australia Aeronautical Data Originator (ADO) portal.
Legislation — CASR
Under regulation 139.005 of the Civil Aviation Safety Regulations 1998 (CASR), CASA may issue a Manual of Standards for Part 139 of CASR that prescribes matters required or permitted by that Part to be prescribed, or necessary or convenient for carrying out or giving effect to Part 139 regulations.
Legislation — Acts Interpretation Act 1901
Under subsection 33 (3) of the Acts Interpretation Act 1901, where an Act confers a power to make, grant or issue any instrument of a legislative or administrative character (like a MOS), the power shall be construed as including a power exercisable in the like manner and subject to the like conditions (if any) to repeal, rescind, revoke, amend, or vary any such instrument.
General safety obligation
Consistently with section 3A of the Civil Aviation Act 1988 (the Act), the main object of a MOS or its amendment is to maintain, enhance and promote the safety of relevant civil aviation, with particular emphasis on preventing aviation accidents and incidents.
To this end, under subsection 9A (1) of the Act, in exercising its powers and performing its functions, CASA must regard the safety of air navigation as the most important consideration.
Background
The ACN-PCN pavement rating method was based on empirical methods of calculating pavement strength originally developed in the late 1930s and early 1940s.
However, the ACN-PCN method is inconsistent with modern pavement design and is being replaced by the ACR-PCR methodology which better allows consistency and alignment between pavement design and pavement rating systems. (See also below under Sector risk, economic and cost impact.)
In December 2018, the International Civil Aviation Organization (ICAO) State Letter (SL) 18/103 proposed amendments to Chicago Convention Annex 14, Volume 1 (Aerodromes — Aerodrome Design and Operations), for the transition from the ACN-PCN pavement rating method to the new ACR-PCR system.
In April 2020, ICAO SL 20/35 informed States that Amendment 15 to Annex 14, Volume 1 had been adopted. This amendment included the changes substituting ACR-PCR for ACN-PCN.
ICAO set the applicability date of the ACR-PCR changes as 28 November 2024. CASA temporarily deferred the change by the submission of a difference to Annex 14, Volume 1. This short-term difference would enable certified aerodromes to transition to the new ACR-PCR system with their amended pavement strength rating values published in the AIP ERSA commencing on 12 June 2025 and being completed on 27 November 2025. A transitional arrangement has been included within Part 139 Manual of Standards Amendment Instrument 2025 (No. 1).
For those aerodrome operators not transitioning, or who choose not to submit their PCR values by the required submission cut-off date of 7 August 2025, the AIP ERSA would, on 27 November 2025, publish their pavements as unrated.
However, they may correct this at a later date by means of a permanent NOTAM or through the Airservices Australia ADO portal.
Details of the MOS amendment
Details of the MOS amendment are set out in Appendix 1. The following is an overview.
Under amendments 1, 2, 3 and 4, definitions of ACN and PCN, and ACR and PCR are inserted, ACR and PCR for the first time, and ACN and PCN as they were before the commencement date but adjusted to accommodate the transition to the ACR-PCR system on 27 November 2025.
Under amendment 5, ACN-PCN and ACR-PCR information to be included in aerodrome manuals is modified to reflect the transitional arrangements.
Consequential on amendment 5, under amendment 6, for the ACR-PCR system, details are prescribed in a new subsection 5.04 (1A), for determining the bearing strength of a pavement intended for aircraft with different maximum take-off weights (MTOWs).
Amendment 7 references section 6.10, under which a runway must be capable of bearing the weights and aircraft movement frequencies of the types of aeroplanes the runway is nominated to serve. A Note refers to paragraph 5.04 (1) (e) which has been amended by amendment 5. Under amendment 7, this Note is consequentially modified to insert mention of ACR and PCR in addition to ACN and PCN, in order to reflect the transitional arrangements.
Legislation Act 2003 (the LA)
Under paragraph 10 (1) (d) of the LA, an instrument that amends a legislative instrument is itself a legislative instrument. The Part 139 MOS is a legislative instrument. Therefore, the MOS amendment is a legislative instrument and subject to registration, and tabling and disallowance in the Parliament, under sections 15G, and 38 and 42, of the LA.
Sunsetting
The MOS amendment relates to aviation safety and, therefore, Part 4 of Chapter 3 of the LA (the sunsetting provisions) does not apply to the instrument (as per item 15 of the table in section 12 of the Legislation (Exemptions and Other Matters) Regulation 2015: “An instrument relating to aviation safety made under the Civil Aviation Act 1988, the Civil Aviation Regulations 1988 or the Civil Aviation Safety Regulations 1998”). The MOS deals with aviation safety matters that, once identified, require a risk response or treatment plan that is intended to have enduring operation and it would not be appropriate for it to be subject to sunsetting. The same principle applies to any amending instrument.
It is likely that further MOS amendments will be made in the foreseeable future and these, while not subject to sunsetting, will be subject to tabling and disallowance in the Parliament in the normal way. CASA would also be responsive to any major concerns expressed by the Parliament about the propriety of the MOS or MOS amendments. Hence, the scope for ongoing parliamentary scrutiny of the Part 139 MOS is not materially reduced.
Incorporation by reference
Under subsection 98 (5D) of the Act, a MOS may apply, adopt or incorporate any matter contained in any instrument or other writing. A non-legislative instrument may be incorporated into a legislative instrument made under the Act, in the terms as that non-legislative instrument exists or as it is in force at a particular time or from time to time (including a non-legislative instrument that does not exist when the legislative instrument is made).
References to provisions of legislation or other legislative instruments are taken to be as they are in force from time to time by virtue of paragraph 13 (1) (c) of the LA. CASR and MOSs are freely available online on the Federal Register of Legislation.
Under subsection 14 (1) of the LA, a legislative instrument may incorporate provisions from another legislative instrument as in force at a particular time, or as in force from time to time.
Under paragraph 15J (2) (c) of the LA, the Explanatory Statement must contain a description of the incorporated documents and indicate how they may be obtained.
Under amendments 3, 4 and 6, the Notes to the definitions mention the guidance document CASA Advisory Circular (AC) 139.C-07: Strength rating of aerodrome pavements (AC 139.C-07), as existing from time to time. This CASA document is freely available on the CASA website.
Under amendment 5, the Note mentions the guidance document ICAO Aerodrome Design Manual (Doc 9157, Part 3), as in force or existing from time to time. This document is a proprietary commercial publication of ICAO available for purchase from the ICAO Store. CASA’s subscription copy may be consulted under appropriate arrangement with CASA.
Under amendment 6, effectively from 27 November 2025, the bearing strength of a pavement intended for aircraft of different MTOWs must be determined and reported using the ACR-PCR method contained in AC 139.C‑07, as in force from time to time. This CASA document is freely available on the CASA website.
Although this is a non-legislative document, a CASA legislative instrument like the MOS amendment, may incorporate such a document, as in force or existing from time to time, by virtue of subsection 98 (5D) of the Act.
Consultation
Under regulation 11.280 of CASR, if CASA intends to issue a MOS, it must, in effect, engage in public consultation on the draft MOS for at least 28 days. This requirement also applies to an instrument that amends a MOS.
Before formal consultation commenced, CASA engaged with certified aerodrome operators both individually through mailouts and personal contact with CASA aerodrome inspectors, and collectively through the National Runway Safety Group (the NRSG) and the Australian Airports Association,
Formal public consultation occurred through publication of the proposed MOS amendments on the CASA website for public comment from 26 March 2025 to 24 April 2025.
Replies were supportive and offered CASA in response the opportunity to revise some drafting in the MOS amendment to clarify the details of the transitional arrangements that would allow aerodrome operators sufficient time to comply with the new arrangements.
Office of Impact Analysis (OIA)
An Impact Analysis (IA) is not required because the instrument is covered by a standing agreement between CASA and OIA under which an IA is not required for amendments to MOSs (OIA id: 14507).
Sector risk, economic and cost impact
Subsection 9A (1) of the Act states that, in exercising its powers and performing its functions, CASA must regard the safety of air navigation as the most important consideration. Subsection 9A (3) of the Act states that, subject to subsection (1), in developing and promulgating aviation safety standards under paragraph 9 (1) (c), CASA must:
(a) consider the economic and cost impact on individuals, businesses and the community of the standards; and
(b) take into account the differing risks associated with different industry sectors.
The cost impact of a standard refers to the direct cost (in the sense of price or expense) which a standard would cause individuals, businesses, and the community to incur. The economic impact of a standard refers to the impact a standard would have on the production, distribution, and use of wealth across the economy, at the level of the individual, relevant businesses in the aviation sector, and the community more broadly. The economic impact of a standard could also include the general financial impact of that standard on different industry sectors.
The new ACR-PCR system enables an optimised usage of aerodrome pavements in terms of allowable aircraft weights and frequencies, both currently and for future pavements without excessive conservatism.
For aircraft operators, subject to any local restrictions, the new rating system will lead to fewer pavement-induced weight restrictions.
For aerodrome operators, it will provide a consistent damage-reduction approach that will:
- optimise the use of aerodrome pavements
- better assess the impact of overload operations
- improve pavement structural life predictions
- ensure new and replacement pavements are designed consistent with contemporary international arrangements.
For aircraft manufacturers, the new rating system will allow them to optimise landing gear geometry (both leg geometry and overall geometry) of their future products.
These benefits all translate to lower costs and overheads for the operators and manufacturers involved without compromising aviation safety.
Environmental impact
Under subsection 9A (2) of the Act, while regarding the safety of air navigation as the most important consideration, CASA must exercise its powers and perform its functions in a manner that ensures that, as far as practicable, the environment is protected from the effects and associated effects of the operation and use of aircraft.
It is not anticipated there will be any negative environmental impacts as a result of the MOS amendment as compared to the baseline that existed in February 2019 before the Part 139 MOS was made.
Statement of Compatibility with Human Rights
The Statement of Compatibility with Human Rights at Appendix 1 has been prepared in accordance with Part 3 of the Human Rights (Parliamentary Scrutiny) Act 2011.
The MOS amendment is compatible with human rights and to the extent that it may engage certain rights it does so in a way that promotes those rights.
Commencement and making
The MOS amendment commences on 12 June 2025.
The instrument has been made by the Director of Aviation Safety, on behalf of CASA, in accordance with subsection 73 (2) of the Act.
Appendix 1
Detailed explanation of:
Part 139 Manual of Standards Amendment Instrument 2025 (No. 1)
1 Name of instrument
This section names the instrument.
2 Commencement
Under this section, the instrument commences on 12 June 2025.
3 Amendment of the Part 139 (Aerodromes) Manual of Standards 2019
Under this section, Schedule 1 amends the Part 139 (Aerodromes) Manual of Standards 2019.
Schedule 1 Amendments
[1] Subsection 3.01 (2), definition of aircraft classification number (ACN)
Under this amendment, the definition of aircraft classification number (ACN), as in force immediately before the 12 June 2025 commencement of the MOS amendment, is preserved until the end of 26 November 2025, and ACN may be reported by aerodrome operators until then.
[2] Subsection 3.01 (2), after the definition of aircraft classification number (ACN)
Under this amendment, the new concept of aircraft classification rating (ACR) is introduced, meaning the number that expresses the relative effect of an aircraft on a pavement for the specified standard subgrade strength of the pavement. ACR-PCR may be reported by aerodrome operators on and from the 12 June 2025 commencement of the MOS amendment if they so choose, but these values must be reported on and after 27 November 2025, or the relevant pavement will be published in the AIP ERSA as unrated
[3] Subsection 3.01 (2), definition of pavement classification number (PCN)
Under this amendment, the definition of pavement classification number (PCN), as in force immediately before the 12 June 2025 commencement of the MOS amendment, is preserved until the end of 26 November 2025, and ACN-PCN may be reported by aerodrome operators until then. A Note references guidance available, as existing from time to time and freely available on the CASA website.
[4] Subsection 3.01 (2), after the definition of pavement classification number (PCN)
Under this amendment, the new concept of pavement classification rating (PCR) is introduced, meaning the number that expresses the bearing strength of a pavement for unrestricted operations. ACR-PCR may be reported by aerodrome operators on and from the 12 June 2025 commencement of the MOS amendment if they so choose, but must be reported on and after 27 November 2025, or the relevant pavement will be published in the AIP ERSA as unrated. A Note references guidance available, as existing from time to time and freely available on the CASA website.
[5] Paragraph 5.04 (1) (e)
Under this amendment, subject to the timing considerations explained in amendments 1 to 4, aerodrome manuals must include the strength rating of the runway pavement calculated using the ACN-PCN or, on commencement if the operator has so chosen, and for all operators not later than 27 November 2025, the ACR-PCR rating system, as applicable.
A Note explains that aerodrome operators have a transition period until the end of 26 November 2025, to adopt the ACR-PCR rating system and report the PCR value. If the PCR value is not reported for the 27 November 2025 date, being the Aeronautical Information, Regulation and Control (AIRAC) date, the relevant pavement will be published in the AIP ERSA as “unrated”.
A second Note adds that guidance on assessing and reporting PCRs is contained in the ICAO Aerodrome Design Manual (Doc 9157, Part 3), as in force or existing from time to time.
[6] After subsection 5.04 (1)
Under this amendment, for paragraph (1) (e) (as amended by amendment 5):
- the bearing strength of a pavement intended for aircraft with an MTOW greater than 5 700 kg must be determined and reported using the ACR‑PCR method contained in AC 139.C-07, as in force from time to time; and
- the bearing strength of a pavement intended for aircraft with an MTOW equal to or less than 5 700 kg may be determined and reported using the ACR-PCR method contained in AC 139.C-07, as in force from time to time.
A Note adds that for an aerodrome operator, determining and reporting the bearing strength of a pavement intended for smaller aircraft is optional, but where it is done it must be done using the ACR-PCR method contained in AC 139.C-07.
[7] Section 6.10, the Note
This amendment is to the Note, and is designed to add mention of ACR-PCR consequentially on amendment 5.
Appendix 2
Statement of Compatibility with Human Rights
Prepared in accordance with Part 3 of the
Human Rights (Parliamentary Scrutiny) Act 2011
Part 139 Manual of Standards Amendment Instrument 2025 (No. 1)
The legislative instruments are compatible with the human rights and freedoms recognised or declared in the international instruments listed in section 3 of the Human Rights (Parliamentary Scrutiny) Act 2011.
Overview of the legislative instruments
The Part 139 (Aerodromes) Manual of Standards 2019 (the MOS) sets out the standards for the construction, maintenance and operation of certified aerodromes, and for the radiocommunications facilities required at aerodromes.
The Part 139 Manual of Standards Amendment Instrument 2025 (No. 1) (the MOS amendment) amends the MOS to incorporate the International Civil Aviation Organization’s new Aircraft Classification Rating (ACR)/Pavement Classification Rating (PCR) system (the ACR-PCR system).
The ACR/PCR system is a new international system for evaluating and reporting the bearing strengths of aerodrome surfaces (runways, taxiways, etc.) that supersedes and replaces the existing aircraft classification number/pavement classification number pavement rating system (the ACN-PCN method).
Aerodrome operators are provided with a transitional period for this change. They may transition to the ACR-PCR system immediately on the 12 June 2025 commencement of the MOS amendment, or they may remain with the ACN-PCN system up until the end of 26 November 2025, beyond which point they must adopt the ACR-PCR system and report the ACR-PCR values or have their relevant aerodrome pavement published as unrated.
The 12 June 2025 instrument commencement date, and the 27 November 2025 transitional cut-off date, are pivotal because they are the Aeronautical Information, Regulation and Control (AIRAC) trigger dates for the publication of pavement values in the Aeronautical Information Publication En Route Supplement Australia.
If the aerodrome operator fails to submit the PCR value by 27 November 2025 and its pavement is published as unrated, they may correct this at a later date by means of a permanent NOTAM or through the Airservices Australia Aeronautical Data Originator portal.
Human rights implications
The MOS amendment engages with the following human rights and freedoms recognised or declared in the international instruments listed in section 3 of the Human Rights (Parliamentary Scrutiny) Act 2011:
- the right to life under Article 6 of the International Covenant on Civil and Political Rights
- the right to safe and healthy working conditions under Article 7 of the International Covenant on Economic, Social and Cultural Rights.
Right to life and the right to safety at work
This engagement is in the context of CASA’s statutory purpose which includes safety relevantly in the air and on the ground. The aim of CASA and its regulatory framework is to uphold aviation safety by regulating the conduct of individuals and organisations involved in civil aviation operations, including operations at aerodromes. It is, therefore, a threshold requirement for all CASA legislative instruments that they preserve, promote and enhance aviation safety.
In the case of the MOS amendment, the new ACR-PCR system is expected to improve the overall safety of aerodrome pavements by more accurately assessing their bearing strength and operating life for the aeroplanes using them. This is expected to translate into better safety outcomes for aircraft, their crews, their passengers, and the personnel directly or indirectly using the pavements.
Human rights implications
The MOS amendment is compatible with human rights, and to the extent that it may engage certain rights, it does so in a way that promotes the right to life and the right to safety at work.
Conclusion
This legislative instrument is compatible with human rights.
Civil Aviation Safety Authority