Maintenance/retirement intervals – proposed under Part 43

Learn more about maintenance/retirement intervals under the proposed general aviation maintenance regulations (Part 43 of the Civil Aviation Safety Regulations 1998 (CASR)) and the Part 43 Manual of Standards.

Who should read this?

  • Registered operators of aircraft to which Part 43 of CASR will apply
  • CAR30 organisations
  • Part 145 approved maintenance organisations
  • Licensed aircraft maintenance engineers

Manufacturer’s instructions for continuing airworthiness (ICAs)

As part of the type certification process, an aircraft manufacturer is required to prepare instructions for continuing airworthiness which set out, among other things, maintenance intervals. Manufacturer’s maintenance instructions (usually the maintenance manual) are set out in the manufacturers ICAs.

Maintenance intervals are divided into manufacturer-recommended maintenance intervals and national aviation authority (NAA)-mandated maintenance intervals, described as Airworthiness Limitations (AWL).

Recommended maintenance actions and frequencies

The recommended maintenance actions and frequencies are required to be provided by the manufacturer in the manufacturer’s ICAs which are accepted by the certifying NAA.

Recommended intervals are required to address inspection intervals for the aircraft and its engines, propellers and components. The manufacturer’s ICAs will also set out recommended overhaul intervals where applicable.

Registered operators (ROs) should familiarise themselves with the manufacturer’ recommendations. However compliance is not mandatory unless an operator is required to, or elects to, use an inspection schedule or inspection program that adopts the aircraft manufacturer’s recommended inspect schedule set out in the ICAs.

Methods, techniques and practices to be used for maintenance

For information regarding the use of manufacturer’s ICAs for maintenance see the information sheet ‘Use of manufacturer’s ICAs’ .

Airworthiness limitations

AWLs set out mandatory retirement times for components and/or mandatory inspections. These mandatory maintenance actions and inspections are approved by the certifying authority and may not be changed unless the changes are also approved by the certifying authority. They are required to be separately identified in an aircraft’s ICAs as mandatory items and accompanied by a statement that they are approved by the certifying NAA.

A reference to an overhaul in the AWLs of the ICAs would make it mandatory. However, overhauls are typically not listed in the AWLs because an overhaul process is a maintenance function, not an AWL.

ROs are responsible for ensuring that AWLs relevant to their aircraft have been complied with at any time the aircraft is to be flown and should familiarise themselves with the AWLs for that aircraft.

The Part 43 Manual of Standards (MOS) requires that any person who performs an inspection or carries out other maintenance specified in an “Airworthiness Limitations” section of the manufacturer’s maintenance instructions issued by the manufacturer of an aircraft must perform the inspection, or carry out the maintenance, in accordance with the section.

The Part 43 MOS also requires that the registered operator must not permit the aircraft to be flown if a maintenance action specified in an Airworthiness Limitations section of the manufacturer’s maintenance instructions has not been completed as required.

Most small simple aircraft, particularly those certified before the 1980s, typically do not have an airworthiness limitations section in their maintenance manuals, however the RO should check the aircraft’s type certificate data sheet – the type certificates and associated data sheets for American manufactured aircraft are available on the Federal Aviation Administration (FAA) website.

From time to time, the certifying NAA for an aircraft may approve a change to the AWLs. For Part 43 aircraft, such changes are not retrospective; they have effect for aircraft manufactured after the date of issue, or sometimes may be specified as affecting aircraft starting with a serial number. Aircraft manufactured before an approved change is made to the AWLs are not affected by the change unless the certifying NAA issues a direction requiring operators to comply with the changes.

Service Bulletins, Service Letters and Service Instructions

On occasion, manufacturers issue service bulletins and may sometimes use phrases such as: “Mandatory Service Bulletin”; “Piper/Cessna/Cirrus considers mandatory” or “FAA approved” however these documents have no legal standing unless:

  • the certifying authority has raised an AD that requires compliance with the same matters
  • the RO is using a maintenance or inspection schedule that requires compliance with the same matters.

Service bulletins are not considered to be ‘manufacturer’s maintenance instructions’ under the Part 43 MOS.

If a manufacturer issues a service bulletin, however described, which recommends a change to a maintenance interval, or an amended instruction for accomplishing a maintenance action, the operator should consider whether the amended information, though not mandatory, may be beneficial to the safety of their type of operations.

Airworthiness Directives

The certifying NAA for an aircraft may decide to make a retirement life or maintenance interval mandatory. When an AD is raised for an aircraft by its certifying NAA, it is binding on affected aircraft in Australia. It should be noted that while changes to an aircraft’s AWLs may not be made retrospective, an AD can expand an amended AWL to include all models of an aircraft, specific models or specific serial numbers.

Type certificate data sheets

Notes in type certificate data sheets (TCDS) define the design of the aircraft and how that design meets its certification basis, not how it is maintained. Some manufacturers include maintenance requirements in a TCDS; however, such information is not mandatory and is not a recognised purpose of a TCDS. Information not specifically referencing the design and configuration of an aircraft, such as information in the form of ongoing maintenance requirements, is inappropriate and not binding on the owner/operator.

FAA Order 8110.121, Type Certificate Data Sheet (TCDS) Notes, explains the intent and design of TCDS notes in greater detail, including descriptions of appropriate content.


The content above has been prepared by CASA for information purposes only and is not the law. It reflects what is proposed to be included in Part 43 of CASR and its associated Manual of Standards which may change at any time and without notice.

When Part 43 is made you should familiarise yourself with its terms. This information is not a substitute for reading the legislation.

CASA accepts no liability for damages or liability of any kind resulting from its use.

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