I, WILLIAM BRUCE BYRON, Director of Aviation Safety, on behalf of CASA, make this instrument under regulation 21 of the Civil Aviation Regulations 1988.

[Signed Bruce Byron]

Bruce Byron
Director of Aviation Safety and
   Chief Executive Officer

17 December 2007

Civil Aviation Order 103.5 Instrument 2007

1 Name of instrument

 This instrument is the Civil Aviation Order 103.5 Instrument 2007.

2 Commencement

 This instrument commences on the day after it is registered.

3 New Civil Aviation Order 103.5

 Civil Aviation Order 103.5 is repealed and a new Civil Aviation Order 103.5 substituted as set out in Schedule 1.

Schedule 1 Civil Aviation Order 103.5

Equipment standards — aircraft equipment software

1 Application

 This Civil Aviation Order specifies design and control standards, under regulations 21, 30, 35 and 36 of the Civil Aviation Regulations 1988 for software contained in aircraft equipment and systems used in Australian registered aircraft.

2 Definitions

 Software, for this Civil Aviation Order, is software resident in aircraft equipment or systems and in use while installed in its operational environment. Software used to control built-in-test functions of equipment is included in this definition.

Note   Operator inputs and database information such as waypoint, DME, aerodrome locations and other such information are excluded from this definition.

3 Design requirements

 3.1Radio Technical Commission for Aeronautics (RTCA) document DO-178A titled, Software Considerations in Airborne Systems and Equipment Certification, provides acceptable guidance on software practices in support of initial certification and post-modification approval of aircraft equipment and system software. The guidance contained in DO-178A, or an equivalent procedure acceptable to the Director, is to be used for initial certification of aircraft equipment and system software.

 3.2Each aircraft equipment and system requiring software must be assigned a Criticality Category and a Software Level which must relate to the severity of the effect on aircraft safety of possible software errors within the equipment or system. Criticality categories and software levels must be assigned in accordance with the criteria defined in DO-178A and must be acceptable to the Director.

 3.3The extent of software configuration management, quality control and assurance must be appropriate to the system criticality category and software level and must be acceptable to the Director.

4 Control requirements

 4.1No change to software must be made for an aircraft system or equipment in the Critical or Essential categories unless:

(a) the change has been made using:

 (i) criteria specified in DO-178A; or

 (ii) equivalent procedures agreed by the Director; and

(b) the change is approved by one of the following:

 (i) the Certification Authority of the state of manufacture; or

 (ii) an authorised person who is authorised to approve changes to software for the specific aircraft equipment or system.

 4.2Software must be treated in the same manner as aircraft components for the purposes of certification, major defect investigation and aircraft component control procedures.

 4.3Modified software must be identified and controlled in accordance with an applicable software configuration management plan as outlined in DO-178A.