Draft AC 139.C-06 v1.0 - Skid resistance of aerodrome pavements and Draft AC 139.C-07 v1.0 - Strength rating of aerodrome pavements (Part 139 consequential ACs)

Closed 10 Sep 2020

Opened 12 Aug 2020

Feedback updated 9 Feb 2021

We asked

The revised Part 139 Manual of Standards (MOS) was made on 05 September 2019. In support of the new rules CASA committed to provide additional guidance material in the form of 'advisory circulars' (AC) to assist aerodrome operators in design, operation, and maintenance of certified aerodromes.

AC 139.C-06 'Skid resistance of aerodrome pavements' and AC 139.C-07 'Strength rating of aerodrome pavements' were subsequently drafted to explain regulatory or standard requirements associated with runway pavements, as well as to provide context for the legislation and its application. It should be noted that the content of an AC is intended to provide good practice and guidance and is not mandatory. CASA acknowledges, in some instances, there may be alternative methods that provide for an acceptable means of compliance, and as such, it is the aerodrome operator's responsibility for determining the best way in which they will meet their regulatory responsibilities.

Between 12 August and 10 September 2020 aerodrome operators, aerodrome consultants and internal CASA personnel, were invited to review the proposed guidance and provide comment on the suitability of the material in support of the revised MOS.

The consultation has closed, and a summary of feedback is provided below. CASA would like to thank industry for providing this feedback.

You said

A total of nine submissions were received— six from consultants and three from aerodrome operators.

Eight respondents consented to their comments being made public, one requested their submission to remain confidential.

Summary of feedback

In addition to recommended changes that were largely editorial in nature, a number of important matters were raised that required further consideration and clarification, these included:

  • requirement to meet surface texture or surface friction characteristics
  • terminology (consistency and definitions) as well as inclusion of references to support content
  • functionality of aircraft tyres in water dispersal
  • phenomenon of aquaplaning
  • surface testing means, locations, frequencies, and the principle of 'averaging'
  • expected timeframes for adopting a new pavement classification system
  • inclusion of information to support assessment of the bearing strength of unrated pavements
  • inclusion of risk-based considerations for pavement concessions.

We did

All comments provided by industry have been carefully considered and where appropriate, incorporated into each AC.

AC 139.C-06 was amended, based on apparent differences in interpretation, to make clear the requirement for surface texture or surface friction testing. Runway grooving is not an acceptable means of compliance in its own right, as they are prone to deterioration over time and even closing up. Grooved runways must meet friction requirements and sealed runways that are not grooved must meet either the minimum standards for surface friction or surface texture.

Sand patch testing has been clarified as the only approved method for measuring surface friction. Should an aerodrome operator seek to utilise an alternate method, CASA approval will be required. The principles associated with establishing an average surface texture depth were further explained. While one test per location is agreed, 'average' refers to within a test location and not across them. The intent is that given the criticality of these areas low texture wheel paths cannot be 'fixed' by averaging with high texture runway edges. Additional guidance was also provided with regard to performing continuous friction measuring equipment (CFME) surveys.

Regarding the life expectancy of sealed pavements, no airport should be planning its maintenance based on 15 years. CASA recommends aerodrome operators should, in addition to complying with the minimum legislative requirements, make their own assessments for the need to conduct additional measured assessments based on the type of aircraft movements and frequency of operations at their aerodrome.

While there was reported confusion by interchangeability of terms skid resistance and friction, it is important to understand that skid resistance equals surface texture and friction, working in combination. Each of the terms are clearly defined in the definitions table and the terms are used very specifically to indicate different issues.

Contrary to feedback received, aircraft tyres do have a tread pattern. Although limited, the circumferential grooves assist in providing escape paths for water.

The phenomenon of aquaplaning was expanded to include explanations on dynamic hydroplaning, reverted rubber, and viscous hydroplaning, as requested, and as a means to assist understanding issues that may require resolution.

To address the question of accuracy, it has been demonstrated that for a dense grade mix, the size of the large stones has very little effect on the macrotexture. This is because the gaps between the larger stones are still filled by the finer particles. Therefore, the resulting texture is almost always 0.4-0.6 mm.

Given the small number of block paving surfaces and, in the absence of full-length concrete runway surfaces in Australia, specific comments on these surfaces were not considered warranted. CASA will consider their inclusion in future revisions.

Additional references were added throughout the document as requested. Aggregate quality assurance was considered beyond the scope of this document, and preparing NOTAMs is addressed in other guidance material.

AC 139.C-07 is about pavement strength rating and is not intended to educate designers. Amendments were made to make clear that the new strength rating system (ACR-PCR) has not yet been adopted by Australia. A target date for implementation (November 2024), has been advised, and CASA will provide ongoing industry education and support well in advance of the transition.

Content was included to support use of APSDS (Airport Pavement Structural Design System) software (commercially developed in Australia) which provides another methodology for the design and construction of aerodrome pavements.

K-values for pavement design are 'indicative' values which come from published literature which has now been referenced.

Equivalence factors relative to the thickness of types of pavement materials have also been referenced as requested, and an example as to how equivalence is applied has been included.

Content from the now redundant AC (139-25(0)) - Strength Rating of Aerodrome Pavements, has been incorporated based on the request for guidance on assessment of bearing strength of unrated pavements.

Further explanation, including an example and referencing, has been provided to explain normalised values with respect to flexible and rigid pavement thicknesses.

Additional guidance has also been included in support of a risk-based decision-making process when considering a pavement concession.

To avoid the potential for erroneous information, ACN values are not included in CASA guidance, this information should be obtained from the airline or aircraft manufacturer as appropriate.

AC 139.C-06 and AC 139.C-07 will be published concurrently with this summary of consultation.

CASA will monitor the effectiveness of the new Part 139 of CASR and the MOS with a view for further revision based on industry feedback and safety outcomes. A post-implementation review is planned to occur after the end of the transition period of 13 November 2022.

Published responses

View submitted responses where consent has been given to publish the response.

Overview

Civil Aviation Safety Amendment (Part 139) Regulations 2019 was made on 21 February 2019.

Effective 13 August 2020, the Part 139 of CASR amendment:

    • establishes a single certification framework for regulated aerodromes (certified)
    • mandates that an aerodrome must be certified based on the publication of a terminal instrument flight procedure
    • sets out the standards for the construction, maintenance and operation of certified aerodromes
    • defines the requirements for aerodrome radiocommunication services at all aerodromes
    • requires the identification of hazards, on aerodromes and within the prescribed airspace. 

The revised Part 139 (Aerodromes) Manual of Standards (Part 139 MOS) was published on 6 September 2019 and will also come into effect on 13 August 2020, replacing the Part 139 Manual of Standards – Aerodromes (version 1.14).

Aerodrome pavements are critical to the safe, efficient and economic operation of the aerodrome. To ensure that hazards to aircraft are minimised they must be constructed and maintained in a suitable condition for the particular demands of the intended aircraft operations.

Advisory Circulars

Advisory Circulars (ACs) will be progressively published and circulated to industry to provide guidance in understanding the new rules.

Through this consultation process CASA invites you to review and provide comment on the following:

  • Draft AC 139.C-06 v1.0 - Skid resistance of aerodrome pavements
  • Draft AC 139.C-07 v1.0 - Strength rating of aerodrome pavements  

Please note, each AC has its own page in this consultation.

Why we are consulting

CASA recognises the valuable contribution that community and industry consultation makes to the regulatory development process. For this reason, we are seeking feedback on whether the draft ACs provide adequate guidance on:

  • skid resistance requirements of aerodrome pavements
  • bearing strength and rating of aerodrome pavements

A copy of each draft AC is provided below and on the survey page for each AC.

Please read the guidance documents before providing your feedback.

Comments should be submitted through the online response form.

Information about how we consult and how to make a confidential submission is available on the CASA website.

To be notified of any future consultations, you can subscribe to our consultation and rulemaking mailing list.

File uploads

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Using an iPad

If you are using an iPad to complete the survey you will be asked to 'download the relevant PDF'. Depending on the software you have on your iPad you may need to download the free viewer to review the single document PDF files. Where a file is a 'multi-file or portfolio PDF you will need to source the Adobe free view - available from iTunes. 

What happens next

At the end of the consultation period, we will review each submission received through the online response form. All submissions will be publicly available on the CASA website, unless you request your submission remain confidential. We will also publish a Summary of Consultation which summarises the feedback received, outlines any intended changes and our plans for the ACs.

Audiences

  • Certified aerodrome owner/operator
  • Registered aerodrome owner/operator
  • CASA aerodrome inspectorate
  • Aerodrome industry consultants
  • Aircraft owner/operator

Interests

  • Operational standards