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Project MS 11/18 - Review of Advisory Circulars & Development of CAAP relating to limited category and experimental aircraft

Topic code: 
Sport & Recreational Standards
Project status: 


This project is now closed.

15 Jan 2013

Project MS 11/18 - Review of Advisory Circulars & Development of CAAP relating to limited category and experimental aircraft

This project is now closed

Refer to the project closure notes for further information.

8 Jan 2013

CAAP 42ZC-2(0) - Maintenance of amateur built aircraft

This CAAP has been published.

15 Nov 2012

Draft CAAP 42ZC-2(0) - Maintenance of amateur built aircraft

Comments on this draft CAAP are to be forwarded to the Project Leader, Mick English by close of business 29 November 2012.

13 Jul 2012

Final AC 21-25(3) - Limited Category Aircraft Permit Index

The final AC has been published.

8 Jun 2012

Draft AC 21-25(3) - Limited category aircraft permit index

Comments on this draft AC are to be forwarded to the Project Leader, Mick English (mick.english@casa.gov.au) by close of business 22 June 2012.

4 Jul 2011

Project MS 11/18 - Review of Advisory Circulars & Development of CAAP relating to limited category and experimental aircraft

Project approved.

Closure notes

Project closed 15 January 2013.

CAAP 42ZC-2(0) - Maintenance of amateur-built aircraft has been finalised

The proposed Advisory Circular regarding flight over populous areas has been converted to a Delegate's procedure.

Advisory Circular 21-25(3) Limited Category Aircraft Permit Index has been finalised.

Future Publications:

  • Advisory Circular 132-1(0) - Limited Category Aircraft Operation will be released as part of advisory material to CASR PART 132 - Limited Category Aircraft (currently under development).
  • Minor amendments to Advisory Circulars 21-4 and 21-5 will be released as part of the advisory material to CASR PART 132.

Review of Advisory Circulars relating to limited category and experimental aircraft:

  1. Develop CAAP 42ZC-2(0) - Amateur built Experimental aircraft-Clarification of maintenance requirements,
  2. Development of a procedure for delegates - Amateur built Experimental aircraft ,flight over built up areas-new procedures and limitations
  3. Limited category aircraft- Introduce updated Permit Index system
  4. Housekeeping changes to AC 21.4(2) and AC 21.5(0)


Amateur built experimental aircraft

Maintenance requirements:

The regulations and associated advisory materials that cover maintenance of amateur built experimental aircraft do not specify in clear terms which classes of person may carry out maintenance on experimental aircraft or what extra maintenance requirements are applicable in relation to amateur built experimental aircraft operating:

  • by night;
  • in IFR; or
  • in other than Glass G airspace

Maintenance is mentioned in Advisory Circular 21.4(2) however the information is cursory in nature and contains inaccuracies (For example, the AC states incorrectly that owner-builders are authorised under CAR 42ZC (6) to carry out maintenance of their aircraft. In fact CAR 42ZC (6) is the head of power under which CASA authorises owner builder maintenance by use of a legislative instrument. Further, that instrument does not confer maintenance rights on an owner-builder unless and until certain conditions are met).

In January 2011, CASA introduced a requirement for owner builder maintainers to undertake a course of training in the regulatory aspects of maintenance and inspection techniques. The new training requirements focus on inspection techniques and maintenance regulatory requirements, based on the assumption that during the course of a normally lengthy construction project the major portion builder has acquired the aircraft systems knowledge and hand skills required to maintain that aircraft. What remains to be addressed in this AC is a means of ensuring that the person has actually constructed the major part of the aircraft.

Flight over built up areas

CAR 262AP and CAO 95.55 state that amateur built experimental aircraft must not fly over built up areas unless authorised by CASA or a CAR 262AP(5) authorised person to do so.

There currently is not a published set of CASA requirements, procedures and limitations for approval of amateur built experimental aircraft for flight over built up areas and due to concerns about the unstructured manner in which some of these approvals have been granted in the past, CASA has decided to withdraw the delegated powers from appointed persons.

Limited category aircraft

AC 21.25(2) prescribes the procedure by which a Permit Index number (P.I.) is allocated to an aircraft. The AC incorporates a table which has pre-allocated a permit Index number to 30 aircraft types, of which only 10 have been approved by an MRB. The remainder of aircraft in the table appear to have been arbitrarily assigned a P.I. number without following the prescribed process, and the resulting Permit Index numbers in some examples are different from the number that would be arrived at for the same aircraft if the instructions and the flow chart in the body of the AC are followed.

The existing Permit Index procedures take into account:

  • Stall speed;
  • Design philosophy;
  • Number of engines; and
  • Maintenance standards.

The AC assessment procedure does not contemplate the maintenance state of individual aircraft and thereby allows potential for a poorly restored, poorly maintained or inappropriately modified aircraft to be assigned a P.I. of 0 when a P.I. of 1, 2 or 3 may be more appropriate.

The AC is silent on matters of glide capability, fuel tank capacity, external tankage and pyrotechnics such as explosive bolts, ejection seats etc which could significantly raise the hazard levels in the event of an accident.

Project Objective

This project has 4 major objectives:

1. Maintenance requirements

The first objective is to draw all the requirements relating to maintenance of amateur built experimental aircraft together in a new Advisory Circular, AC21.xx - MAINTENANCE OF AMATEUR BUILT AIRCRAFT.

In conjunction with the new AC it will be necessary to amend existing ACs 21.4 (2) and 21.10 (1) to remove advice that is either inaccurate or has been made redundant by the new circulars. This project also aims to incorporate in the maintenance AC, a requirement for an Authorised Person to be involved in the project from start to finish and at a sufficient level of involvement to be able to satisfy him/herself that the builder has constructed the major part of the aircraft and acquired thereby, the necessary knowledge and hand skills. The tightening up of the major portion requirement in conjunction with the newly introduced training requirements will ensure that persons who maintain their aircraft will possess sufficient competencies to maintain the aircraft as a minimum, at the standards to which it was constructed.

2. Flight over built up areas

The second project objective is to introduce a set of parameters and procedures for the assessment of applications by operators of amateur built experimental aircraft for approval under CAR 262 AP(5) to fly over built up areas. It is proposed to achieve this by publishing a new advisory circular, AC21.xx - AMATEUR BUILT EXPERIMENTAL AND CERTAIN ULTRA LIGHT AIRCRAFT- FLIGHTS OVER BUILT UP AREAS.

The procedures are intended to thoroughly address CASA concerns by specifying in detail, the assessment criteria to be applied to the type of aircraft, engine, PSRU (where applicable) and propeller. A standardised set of eligibility parameters and assessment criteria and procedures will address CASA concerns about the currently unstructured and in some cases arbitrary granting of CAR 262 AP (5) approvals.

3. Limited Category Aircraft Permit Index

The third project objective is to amend AC 21.25(2) by deleting the table at attachment 3 and introducing extra risk assessment protocols.

The amended AC will introduce a range of extra parameters to be considered when assessing both the level of risk of failure in flight and the potential damage to persons and property in the event of an accident arising out of a failure.

The outcome will be a more comprehensive risk assessment and mitigation process that will take into account factors such as engine type, fuel type & capacity, operational and maintenance history, dangerous goods on board, glide ratio, engine out capabilities, etc.

Risk Management Standard: The review of the AC will take into account the recognised international risk management standard ISO31000:2009 and will also consider applicable elements of AS/NZS 4801 OH&S, AS/NZS 4804 OH & S, and AS/NZS 4360 Risk management.

4. Housekeeping - Passenger warning requirements

Passenger warning requirements for experimental aircraft as described in AC 21.4(2) and limited category aircraft as described in AC 21.5(0) do not conform to the requirements set out in the relevant legislation. (CAR 262 AM and CAR 262 AP). These anomalies will be rectified as part of this project.


This project was approved by Peter Boyd on 1 July 2011.

Project management

Project Leader: Mick English

Project Sponsors:

Greg Hood, Executive Manager CASA Operations

Jonathan Aleck - Associate Direction of Aviation Safety

Mark Taylor - Manager Delegations Management Branch

Standards Development Project Manager: Andrew Ward, Senior Standards Officer, Sport Aviation & Small Aeroplanes

Project Priority