Civil Aviation Order 103.20 Instrument 2007

Cockpit voice recorder system. The Instrument defines this as including flight deck mounted equipment (control unit, monitor display, microphones, area microphone, preamplifiers) and a crash protected recorder. The system must be approved as a whole, but the technical specifications focus predominantly on the recorder’s performance and the installation’s recording architecture.

Four channel recording. The core requirement is simultaneous recording on at least four separate channels. Each channel is assigned specific audio sources: channel 1 from the first pilot station; channel 2 from the second pilot station; channel 3 from a flight deck mounted area microphone; channel 4 from third and fourth crew member stations, or from other flight deck stations with audio selection and transmit facilities, or from the passenger address system microphones if those stations are not required. The separation ensures that investigators can later distinguish which crew member spoke and what ambient sounds occurred.

Hot microphone. For most microphones (excluding hand held types with an ON/OFF switch), all sounds received must be recorded regardless of the position of the Radio Transmission/Intercommunication Selector switch. This is labelled “hot” in the industry. The requirement is designed to capture spontaneous speech and non verbal sounds that might be missed if the microphone were only active when transmitting. The wiring must produce side tone only when radio transmission or intercommunication is selected, and must avoid unwanted coupling between microphone and headset circuits.

Area microphone. A separate microphone mounted centrally forward of a vertical plane through the pilots’ normal sitting positions, designed to pick up general cockpit sounds and crew speech. Its location must account for the presence and signal strength of flight deck loudspeakers to avoid obliterating other signals. The goal is to capture ambient noise and conversation not directed at a specific headset, which can be critical in accident analysis.

Technical Standard Order C84. The recorder hardware must comply with FAA TSO C84 or a later amendment. This standard covers crash survivability, fire resistance, underwater locator beacons, recording duration, and data integrity. The Instrument does not reproduce these specifications but incorporates them by reference, meaning that compliance depends on the current version of the TSO adopted by CASA approval.

First of type flight test. Before an aircraft/recorder system combination receives approval, the operator must conduct a flight test covering taxiing, takeoff, cruise, approach, landing, and for helicopters hover and auto rotation. The test must follow a prescribed script with specific announcements, microphone selections, and system activations (e.g., stall warning stick shaker, overspeed warning, navigation aid selection). The recorded tape is sent to the ATSB for analysis, which will confirm adequate quality on all channels. The ATSB retains the original tape as a reference for that aircraft type/recorder combination.

30 minute recording limit. The Instrument notes that the CVR tape duration is limited to 30 minutes. During the flight test the circuit breaker must be tripped between phases to preserve tape for each segment. This reflects older tape based technology; the Instrument does not mandate a minimum recording duration in section 3, but the flight test procedure assumes 30 minutes. Modern solid state CVRs typically record two hours, but the Instrument’s test procedure would still apply if such a unit is installed.

Erasure facility. The flight deck must have a means to erase the record after the aircraft stops on the ground. The installation must be designed to prevent in flight erasure and to minimise inadvertent erasure during crash impact. The automatic stop feature must simultaneously stop the recorder and prevent erasure within 10 minutes after crash impact.

The Instrument directly affects several groups. Aircraft operators are the principal duty holders. Any operator of an Australian aircraft that requires a CVR under CAO 20.18 must ensure that the installed system meets these standards. This includes airlines, charter operators, air taxi services, and private operators of aircraft that carry passengers or are used in certain commercial operations. The compliance cost falls on them: they must purchase approved recorders, pay for installation and wiring, and for new combinations arrange and fund the flight test and ATSB analysis. The Instrument does not differentiate by operator size, so a small operator with a single aircraft shoulders a proportionately heavier compliance burden than a large airline.

Maintenance and installation organisations must design and carry out the installation to the precise specifications. This includes wiring the four channels with the correct assignment, ensuring hot microphone configuration, mounting the area microphone in the optimal position, connecting the recorder to the most reliable electrical bus, and installing the automatic crash stop mechanism. The requirement for the recorder to be located as far aft as possible can conflict with other installation needs (e.g., cargo or baggage compartments) and may require structural modifications. Maintenance organisations must also incorporate the pre flight monitoring check into flight deck procedures.

Flight crew are affected in two ways. First, they must include a CVR operational check as part of the pre flight procedure (section 3.4(b)). Second, during the first of type flight test, crew must perform the detailed script and announcements. The Instrument also affects crew privacy: recordings made during the flight test may be released to the operator’s engineering organisation and the ATSB, and the consent of crew is assumed unless they give written restrictions. This creates a privacy risk for crew, especially if recordings capture conversation beyond the test script.

Manufacturers and designers of CVRs and aircraft must ensure that the recorder meets TSO C84 (or later) and that the overall system design, including microphones, preamplifiers, and wiring, can achieve the four channel separation and hot microphone performance. The Instrument does not prescribe approval procedures for the system as a whole, but the flight test requirement means that each new combination must be individually approved by the Director through the ATSB analysis report.

The Australian Transport Safety Bureau is given a central role in the flight test regime. It must perform the replay and analysis, ensure privacy of recordings, issue a report, and retain the original tape as a reference. This creates a resource obligation on the ATSB, which must allocate skilled personnel and equipment to process these tests. The Instrument does not specify a service standard or cost recovery mechanism, so the time and cost of obtaining a report is uncertain for operators.

CASA is the rule maker and approval authority. The Director must approve the type of recorder (section 2.3). CASA also retains enforcement power: since the Instrument is made under the Civil Aviation Regulations 1988, non compliance can lead to enforcement action, potentially including suspension or revocation of the aircraft’s certificate of airworthiness.

Duty to use an approved recorder. The CVR must be of a type approved by the Director and comply with TSO C84 or later amendment (section 2.3). This means an operator cannot simply install any recorder that meets generic performance standards; it must be one that CASA has specifically approved. The approval process is not described in the Instrument, but it presumably involves submission of technical data by the manufacturer.

Duty to install to the prescribed channel architecture. Section 3.1 sets out exactly which audio sources go to which channel, with fallback rules if fourth crew stations are not required. The installer must ensure that each channel receives only its designated sources, and that the wiring avoids unwanted coupling and side tone issues. The hot microphone requirement (section 3.1(b)) means that for most microphones the recording must be continuous regardless of switch position, with side tone only when transmitting or in intercom.

Duty to locate and power the recorder correctly. The recorder must be powered from the bus that provides maximum reliability without jeopardising essential or emergency loads (section 3.4(a)). It must be installed as far aft as possible to minimise crash and fire damage (section 3.5). The note cautions about engines, baggage, cargo and structural collapse, but these are not legally binding as they appear in a note. However, the duty to minimise probability of damage is binding, so a location that violated this principle would be non compliant.

Duty to install crash stop and erasure prevention. Section 3.4(c) requires an automatic means to stop the recorder and prevent erasure within 10 minutes after crash impact. Section 3.6 requires an erasure facility on the flight deck for ground use, but the installation must prevent in flight erasure and minimise inadvertent erasure during crash impact. The interplay between these two duties means the erasure button must be disabled or overridden by the crash stop mechanism. Designers must ensure that a crash does not mechanically or electrically trigger the erase function.

Duty to conduct flight test for first of type. For the first installation of a new aircraft/recorder combination, the operator must conduct the flight test in Appendix I and have the recording analysed by the ATSB (Appendix I section 3). This duty arises before CASA gives approval for that combination. The cost and logistical effort of arranging the test, providing a test schedule, and sending the tape to the ATSB rests with the operator. The Instrument does not specify a timeline for the ATSB to produce the report, creating uncertainty.

Duty to respect crew privacy. The Instrument grants flight crew the right to give written instructions stating restrictions on release of recordings (Appendix I section 1.6). If no such instructions are given, the crew is assumed to consent to release to the operator’s engineering organisation and the ATSB. This right is limited: it does not apply to recordings made during normal operations (only during the flight test), and it does not prevent the ATSB from using the recording for analysis. Crew who wish to restrict release must actively provide written instructions before the test.

Right to obtain a report from the ATSB. The applicant (operator) is entitled to a report from the ATSB confirming that all input channels were identified and noting any other observations (Appendix I section 3.3). The report is likely essential for obtaining CASA approval of the installation.

The Instrument itself does not contain penalty provisions. It is made under subregulation 21A(1) of the Civil Aviation Regulations 1988 (CAR 1988). Accordingly, failure to comply with any requirement of the Instrument is a breach of the CAR 1988. Regulation 21A of CAR 1988 is a general power to make orders, and breaching an order is an offence under regulation 269 of CAR 1988, which specifies a penalty of 50 penalty units for a natural person and 250 penalty units for a body corporate. However, the exact penalty may be subject to amendment and cross referencing to the Civil Aviation Act 1988, which provides for civil penalty provisions and infringement notices.

In practice, CASA can take enforcement action if an aircraft operates with a CVR that does not meet these standards. The most immediate practical enforcement action is likely to be the refusal or suspension of the aircraft’s certificate of airworthiness. Since the CVR requirement flows from CAO 20.18, which mandates installation of a CVR in specified aircraft, non compliance with the equipment and installation standards under this Instrument means the aircraft does not have a compliant CVR, and therefore does not meet its certificate of airworthiness requirements. CASA could also issue a direction to ground the aircraft, impose a civil penalty, or initiate criminal prosecution if the breach is deliberate or reckless.

The enforcement risk is concentrated on operators and maintenance organisations. The hot microphone and channel assignment requirements are particularly subject to interpretation, and an inspector may discover during a ramp check or post accident inspection that wiring does not meet the precise specifications. The note about hand held microphones (exempt from hot microphone) could create a misconception that other microphones are also exempt.

The Instrument’s role in accident investigation adds an indirect enforcement dimension. The ATSB, when replaying recordings under Appendix I, will detect any installation deficiencies. While the ATSB is not an enforcement body, its findings could be referred to CASA. Moreover, if a recording fails to capture necessary audio in an accident, the operator faces significant reputational and legal liability beyond the regulatory penalty.

Civil Aviation Order 20.18. This is the primary requirement that drives the application of the Instrument. Section 1.1 states that the Instrument applies to CVRs installed in compliance with CAO 20.18. An operator first checks if CAO 20.18 requires a CVR for the aircraft; if so, the CVR must meet these standards. The Instrument does not supplement or override CAO 20.18 but rather fills in the technical details.

Civil Aviation Regulations 1988. As noted, the Instrument is made under subregulation 21A(1) of CAR 1988. Any breach is a breach of the CAR 1988. Additionally, the flight test requirement and approval of recorder types may interact with other CAR provisions on aircraft modifications and continuing airworthiness (Part 4A and 4B). The installation of a CVR is likely a modification that requires an approval under regulation 35A or 35B of CAR 1988.

Civil Aviation Act 1988. The Act provides the overarching enforcement framework, including civil penalties (Part IVB) and infringement notices (Part IVC). It also gives CASA the power to issue airworthiness directives and directions. If a particular CVR model or installation method is found to be non compliant, CASA could issue an airworthiness directive mandating corrective action.

Transport Safety Investigation Act 2003. The Instrument gives the ATSB a specific role under Appendix I in analysing flight test recordings and retaining reference tapes. The ATSB operates under this Act, which includes provisions for protecting the privacy of recordings and limiting their use for administrative or enforcement actions. The Instrument’s procedure assumes the ATSB will ensure privacy, consistent with section 23 of the Transport Safety Investigation Act, which prohibits disclosure of certain information. However, the Instrument allows release to the operator’s engineering organisation, which may not be permitted under the Act without consent. This creates a potential conflict if the ATSB’s broader statutory obligations prevent release.

Privacy Act 1988. The recording of flight crew conversations during the flight test raises privacy considerations. The Instrument assumes consent unless crew give written restrictions. This may not be sufficient to comply with the Australian Privacy Principles if the operator is an agency or organisation subject to the Privacy Act. Crew members could argue that their consent was not freely given because participation in the test is a condition of employment. Operators carrying out flight tests should obtain explicit written consent from crew members.

FAA Technical Standard Order C84. This is an external standard incorporated by reference. Changes to TSO C84 (e.g., a later amendment) are automatically adopted by the Instrument (section 2.3). Operators and manufacturers must keep track of FAA amendments to TSO C84 to ensure their equipment remains approved. If CASA later requires a different TSO, it would need to amend this Instrument.

Other Civil Aviation Orders. The Instrument does not reference CAO 103.21 (flight data recorders) or CAO 103.22 (combination recorders). However, if an aircraft is required to have both a CVR and a flight data recorder, and if a combination recorder is used, the CVR portion must still comply with this Instrument. The interaction with other CAOs on recorder maintenance and data download is not addressed here.

The Instrument was made on 17 December 2007 by William Bruce Byron as Director of Aviation Safety and CEO of CASA. It commenced on the day after it was registered on the Federal Register of Legislative Instruments. Its core effect was to repeal the previous Civil Aviation Order 103.20 and substitute a new version set out in Schedule 1. The text of the earlier CAO 103.20 is not reproduced, so we cannot compare the changes. However, the Instrument notes that it applies to aircraft receiving initial Australian Certificate of Airworthiness after 1 January 1985. That date was likely carried over from the previous order, meaning the Instrument did not change the scope of aircraft affected.

No further amendments to this Instrument are recorded in the text provided. The Instrument has been in force for over 15 years. Given the age of the underlying technology (30 minute tape, TSO C84), it is likely that the Instrument has been amended or superseded since 2007. However, based solely on the source, there is no amendment history. Practitioners should check the current version of CAO 103.20 on the Federal Register of Legislation.

The Instrument is a standalone legislative instrument made under regulation 21A of CAR 1988, not an Act of Parliament. As such, it can be amended by CASA without parliamentary approval, subject to the Legislative Instruments Act 2003 (now the Legislation Act 2003). The 2007 version replaced the earlier order completely, showing that CASA can make substantial changes through this mechanism.

The source contains no references to any litigation. The Instrument sets technical standards for equipment; challenges to such standards are rare because they are prescriptive and typically uncontroversial in court. However, litigation could arise in three scenarios.

First, a dispute between an operator and CASA over whether an installation meets the requirements, particularly the hot microphone configuration, channel assignment, or area microphone location. The operator might seek judicial review of CASA’s refusal to approve an installation, or CASA might take enforcement action that the operator defends. The Instrument’s language is mostly objective, but there is some subjectivity (e.g., “the gain should be adjusted such that… the microphone signal exceeds the level of the headset side tone signal from other sources on a high percentage of occasions” - section 3.1(b)(iii)). That standard could be contested.

Second, a privacy claim by flight crew over the release of recordings under the Instrument’s flight test procedure. Section 1.6 of Appendix I assumes consent unless the crew gives written restrictions. A crew member might argue that this does not comply with the Privacy Act or that the consent was coerced. If the ATSB releases the tape to the operator’s engineering organisation, the crew might sue for breach of privacy. The Instrument would likely not override the Privacy Act, so such a claim could succeed.

Third, liability arising from an accident where the CVR failed to record or recorded inadequately due to non compliance with the Instrument. Relatives of victims might argue that the operator’s breach of the Instrument caused a failure to capture crucial evidence, prejudicing the investigation and the ability to determine the cause. This would be a novel claim in tort, as the purpose of the Instrument is safety, and a breach might be evidence of negligence. However, no such case has been identified.

Absent any published decisions, the litigation history is effectively nil. Practitioners should be aware that the Instrument’s vaguer requirements could become the subject of litigation if CASA takes a strict enforcement stance or if privacy rights are violated.

The 30 minute recording limit. The Instrument’s flight test procedure assumes a 30 minute tape. Modern solid state CVRs commonly record at least two hours. However, the Instrument’s design requirements do not mandate a minimum recording duration. If an operator installs a modern CVR that records longer, they must still show that the system meets the channel assignment and quality standards. The flight test procedure (Appendix I) must be adapted (section 1.4: “may need to be adapted to suit the particular installation being tested”). This flexibility is a gotcha because the operator cannot simply follow the Appendix I script verbatim; they must consider the recording duration and adjust the test accordingly. Failure to do so may result in an incomplete demonstration.

The hot microphone exemption for hand held microphones. The note to paragraph 3.1 states that paragraph 3.1(b) (hot wiring) does not apply to hand held microphones with an ON/OFF switch. Operators and installers might incorrectly assume that other hand held microphones without an ON/OFF switch, or microphone types not listed, also qualify for the exemption. They do not. The exemption is narrow and applies only to hand held microphones that incorporate a switch that physically breaks the microphone circuit. All other microphones, including boom microphones, oxygen mask microphones, and area microphones, must be hot wired.

Side tone specification. Section 3.1(b)(i) requires that side tone is produced only when Radio Transmission or Intercommunication is selected. This prevents the crew from hearing their own voice through the headset when not actually transmitting or using intercom. However, the side tone is produced from the microphone signal, and the wiring must ensure that the side tone path is not inadvertently active at other times. A poorly designed installation could cause side tone to be heard during announcements or other audio events, potentially distracting the crew.

Automatic stop within 10 minutes of crash impact. The requirement (section 3.4(c)) is deceptively simple. The automatic means could be a G switch or impact sensor that triggers the stop. The design must also prevent any erasure feature from functioning after activation. This means the erasure button on the flight deck must be disabled by the crash stop. If the erasure function is electrical, the crash stop may need to physically break a circuit. The 10 minute window must be guaranteed, and the system must survive the crash to achieve this.

Crew privacy assumption. The Instrument states that the agreement of flight crew is assumed unless instructions are given in writing (Appendix I section 1.6). This places the burden on the crew to opt out. Many crew members may not be aware of this, or may not know they can restrict release. The operator should inform crew before the flight test and obtain explicit consent, regardless of the Instrument’s assumption, to avoid later disputes.

Noise intelligibility standard. The quality of recording must be “as high as practicable” (section 3.3). This is a relative standard, not an absolute one. It could be argued that if better technology exists, the operator should use it to achieve higher quality. However, the Instrument does not require a specific signal to noise ratio or intelligibility score. The flight test is the only place where quality is objectively assessed, and that assessment is performed by the ATSB. An operator who passes the flight test may later face a dispute about quality in an accident investigation if the recording is found inadequate.

Documentation requirements for flight test. The tape must be sent to the ATSB accompanied by a copy of the test schedule, the manufacturer and model of the CVR, and the position of the area microphone (Appendix I section 3.1). If any of these are missing, the ATSB may refuse to perform the analysis or may produce an inconclusive report. The operator must also state any restrictions from flight crew. Failure to provide this documentation could delay approval and require a second flight test.

Approval of recorder type. The Instrument requires the CVR to be of a type approved by the Director (section 2.3). It does not specify that an approval must be obtained for each specific model or that the approval must be in writing. An operator might assume that any recorder meeting TSO C84 is automatically approved. However, the Director must specifically approve the type; this approval may involve a CASA design certificate or a letter of approval. Operators should confirm with CASA that their chosen recorder is approved.

Step 1: Determine applicability. Confirm that the aircraft is required to carry a CVR under CAO 20.18. Only then does the Instrument apply. The aircraft must also have received its initial Australian Certificate of Airworthiness after 1 January 1985 (section 1.2). If the aircraft is older, the earlier CAO 103.20 may apply, depending on any transitional provisions not shown in this Instrument.

Step 2: Select an approved recorder. Choose a CVR that meets FAA TSO C84 or a later amendment, and that is of a type approved by CASA’s Director. Obtain evidence of approval, such as a CASA design acceptance. Ensure the recorder includes a crash protected container coloured bright orange or bright yellow with reflective tape (section 2.4). Also ensure it has an automatic stop and erasure prevention feature that triggers within 10 minutes of crash impact.

Step 3: Design the installation. The installation must provide four separate channels with the source assignments listed in section 3.1(a). For each channel, route the appropriate microphone and audio signals. Ensure that for the microphones listed in 3.1(a)(i), (ii), (iv) and (v) (excluding hand held microphones with a switch), the wiring is hot: all sounds are recorded regardless of the Radio Transmission/Intercommunication selector position. Adjust impedances and signal levels to avoid unwanted coupling. Set gain so that microphone signals exceed headset side tone on a high percentage of occasions. The area microphone must be positioned centrally forward of a vertical plane through the pilots’ normal sitting positions, considering loudspeaker locations and signal strength to avoid obliteration (note to section 3.2).

Power the recorder from the bus providing maximum reliability without endangering essential or emergency loads (section 3.4(a)). Fit a means for the crew to monitor proper operation as part of the pre flight procedure (section 3.4(b)). Install the recorder as far aft as possible to minimise crash and fire damage, with maintenance access reasonable (section 3.5). Install a flight deck erasure facility that cannot be used in flight and is designed to minimise inadvertent activation during a crash (section 3.6). The automatic stop must simultaneously stop the recorder and prevent erasure.

Step 4: Conduct a flight test (if first of type). If this is the first installation of the specific aircraft/recorder combination, you must organise a flight test per Appendix I. Prepare a test schedule. Inform flight crew of the test and obtain written consent or note any restrictions. Perform the test script, including engine start, takeoff, cruise, helicopter specific maneuvers, and landing. Trip the CVR circuit breaker between phases to stay within 30 minutes of tape (or adapt if using a longer duration recorder). Do not erase after landing; pull the circuit breaker.

Send the tape or recording to the ATSB with a copy of the test schedule, manufacturer and model of the CVR, and area microphone position. The ATSB will analyse and provide a report confirming channel identification and adequate quality. The original tape will be retained by the ATSB.

Step 5: Obtain installation approval. The flight test report is likely required for CASA to approve the installation. Even if the combination has been previously approved in another aircraft, the Instrument does not waive the flight test requirement. However, the Instrument only requires the flight test for “first of type aircraft/recorder system combination” (Appendix I section 1.1). If the combination has been previously approved in another Australian aircraft, the operator may not need to repeat the flight test. Confirm with CASA.

Step 6: Maintain ongoing compliance. Incorporate the CVR check into the pre flight procedure (section 3.4(b)). Ensure that maintenance personnel do not alter the hot microphone wiring or channel assignments without re approval. Keep records of the approved recorder type, installation details, and flight test report. If the CVR is replaced with a different model, the combination may become a new first of type, requiring another flight test. Monitor FAA updates to TSO C84, as a later amendment may require a new approval if the recorder’s TSO is superseded.