AC 20-186A

U.

S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Airworthiness and Operational Approval of Cockpit Voice Recorder Systems Date: 5/6/24 AC No: 20-186A Initiated by: AFS-300 Change:

This advisory circular (AC) provides guidance for gaining airworthiness approval for cockpit voice recorder (CVR) systems. Specifically, when followed in its entirety, it provides an acceptable means for complying with the airworthiness regulations contained in Title 14 of the Code of Federal Regulations (14 CFR) parts 23, 25, 27, 29, 91, 121, 125, 129, and 135 when installing CVR systems in airplanes and rotorcraft. As CVR systems and technology advance, applicants are encouraged to propose alternative methods to their responsible Aircraft Certification Service office to integrate new and novel safety enhancing CVR systems and functions into their aircraft. The responsible Aircraft Certification Service office will evaluate alternative methods consistent with the Federal Aviation Administration’s (FAA) safety continuum. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies. This AC is not mandatory and does not constitute a regulation.

H ugh Thomas for Lawrence Fields Executive Director, Flight Standards Service

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CONTENTS Paragraph Page

Chapter 1. Introduction1-1

1.1 Purpose of This Advisory Circular (AC)1-1

1.2 Audience1-1

1.3 Where You Can Find This AC1-1

1.4 What This AC Cancels1-1

1.5 How to Use This Document1-1

1.6 Definitions, Acronyms, and Related Documents1-3

1.7 AC Feedback Form1-3

Ch apter 2. Type Certification2-1

2.1 Purpose of This Chapter2-1

2.2 CVR Substantiating Data2-1

2.3 Intended Function2-2

2.4 Demonstrate Performance2-3

2.5 Equipment2-4

2.6 Combination CVR/FDR Systems2-4

2.7 DLR2-4

2.8 Weight and Balance (W&B)2-5

2.9 Electrical Load Analysis (ELA)2-5

2.10 Electrical Power Sources2-6

2.11 Circuit Protection Devices2-6

2.12 Preflight Monitoring2-6

2.13 Flight Manual Applicability2-6

2.14 ICAs as Part of Substantiating Data2-6

2.15 Removal and Replacement2-7

2.16 ULD Installation and Maintenance2-7

2.17 Installation Design2-8

2.18 Electrical Wiring Interconnection System (EWIS)2-8

Ch apter 3. Continued Airworthiness Requirements3-1

3.1 Purpose of This Chapter3-1

3.2 Continuous Airworthiness3-1

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3.3 Configuration Control3-3

3.4 ICA3-4

3.5 Storage3-4

Appendix A. D efinitions, Acronyms, And Related DocumentsA-1

Appendix B. Fl owchartsB-1

L ist of Figures

Figure B-1. Aircraft by Operating RulesB-1

Figure B-2. P art 91B-2

Figure B-3. Part 121B-3

Figure B-4. P art 121, 10–19 Passenger SeatsB-4

Figure B-5. Part 121, 20–30 Passenger SeatsB-5

Figure B-6. Part 125B-6

Figure B-7. Part 135B-7

1-1 CHAPTER 1. INTRODUCTION

1.1 Purpose of This Advisory Circular (AC).

1.1.1 A cockpit voice recorder (CVR) system records the aural environment of the cockpit and communications to, from, and between flight crewmembers and, in some cases, required data link messages to assist investigations of accidents and incidents. The objective is met by complying with the current requirements in Title 14 of the Code of Federal Regulations (14 CFR) parts 23, 25, 27, 29, 91, 121, 125, 129, and 135.

1.1.2 This AC provides guidance for compliance with applicable regulations for the airworthiness and operational approval for required CVR systems. Optional installations may use this guidance when installing a CVR system as a voluntary safety enhancement.

1.1.3 Applicants may propose alternate means. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies.

1.1.4 As CVR systems and technology advance, applicants are encouraged to propose alternative methods to their responsible Aircraft Certification Service office to integrate new and novel safety enhancing CVR systems and functions into their aircraft. The responsible Aircraft Certification Service office will evaluate alternative methods consistent with the Federal Aviation Administration’s (FAA) safety continuum.

1.2 Audience. The FAA is publishing this AC for aircraft manufacturers; CVR system manufacturers; aircraft operators; maintenance, repair, and overhaul (MRO) organizations; and Supplemental Type Certificate (STC) applicants.

1.3 Where You Can Find This AC. You can find this AC on the FAA’s website at https://www.faa.gov/regulations_policies/advisory_circulars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov.

1.4 What This AC Cancels. AC 20-186, Airworthiness and Operational Approval of Cockpit Voice Recorder Systems, dated July 22, 2016, is canceled.

1.5 How to Use This Document.

1.5.1 Sections of parts 23, 25, 27, 29, 91, 121, 125, 129, and 135 detail design substantiation and operational approval requirements directly applicable to the CVR system. See Appendix B, Flowcharts, to determine the applicable regulations for your aircraft and type of operation. Listed below are the specific 14 CFR sections addressed in this AC (however, there may be additional sections related to this subject matter that should be considered):

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1. Part 23:

• Section 23.1457, Cockpit Voice Recorders.

• Section 23.1529, Instructions for Continued Airworthiness.

• Section 23.2505, Function and Installation.

2. Part 25:

• Section 25.1301, Function and Installation.

• Section 25.1457, Cockpit Voice Recorders.

• Section 25.1529, Instructions for Continued Airworthiness.

3. Part 27:

• Section 27.1301, Function and Installation.

• Section 27.1457, Cockpit Voice Recorders.

• Section 27.1529, Instructions for Continued Airworthiness.

4. Part 29:

• Section 29.1301, Function and Installation.

• Section 29.1457, Cockpit Voice Recorders.

• Section 29.1529, Instructions for Continued Airworthiness.

5. Part 91:

• Section 91.609, Flight Data Recorders and Cockpit Voice Recorders.

• Section 91.1045, Additional Equipment Requirements.

6. Part 121, § 121.359, Cockpit Voice Recorders.

7. Part 125, § 125.227, Cockpit Voice Recorders.

8. Part 129, § 129.24, Cockpit Voice Recorders.

9. Part 135, § 135.151, Cockpit Voice Recorders.

1.5.2 In order to meet the CVR regulations in 14 CFR, equipment manufactured after December 19, 2013, must meet the minimum performance standards (MPS) qualification and documentation of EUROCAE Document (ED)-112A, Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems, as detailed in Technical Standard Order (TSO)-C123c, Cockpit Voice Recorder Equipment, and this AC.

1.5.3 The FAA is initiating the phasing out of magnetic tapes through both mandates and voluntary efforts to replace them with modern solid-state recorders. These new recorders not only enhance safety but also benefit the operator directly, as they avoid the high costs and technical problems of maintaining outdated recorders. Modern recorders do not require the hourly replacement of tapes and calendar weighing of thermal capsules.

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1.5.4 This AC is based on the technical standards referenced in EUROCAE ED-112A and the Code of Federal Regulations (CFR).

1.5.5 When using documents referenced in this AC, the applicant should use the most current version of the document cited.

1.5.6 The material in this AC does not alter or subvert any regulatory requirements.

1.5.7 This AC describes CVR system performance.

1.5.8 Appendix B provides a set of flowcharts to aid the reader in determining if a CVR is required to be installed.

1.6 Definitions, Acronyms, and Related Documents. Definitions, acronyms, and related documents can be found in Appendix A, Acronyms and Related Documents.

1.7 AC Feedback Form. For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.

2-1 CHAPTER 2. TYPE CERTIFICATION

2.1 Purpose of This Chapter. This chapter provides information for type certification of a CVR system. The applicant must obtain FAA approval to install or retrofit a CVR and components. The applicant may apply for a type certificate (TC), amended TC, Supplemental Type Certificate (STC), or other manner of approval, and the applicant must demonstrate compliance with the applicable regulations included in the type certification basis for the aircraft. The applicant may use Appendix B, Flowcharts, as an aid to determine CVR certification requirements based on the operating rules under which the applicant’s aircraft operates. An applicant must demonstrate compliance with the appropriate certification requirements.

2.2 CVR Substantiating Data. Technical Standard Order (TSO)-C123c, Cockpit Voice Recorder Equipment, describes a means to substantiate data needed to describe the CVR system. If TSO-C123c is not used, the applicant should provide a description that includes:

1. The make and model or part number of the CVR or combination CVR/flight data recorder (FDR);

2. A listing of each channel recorded and its duration;

3. A list of additional information recorded (image or data link);

4. Identification of power source or sources;

5. Description of independent power source;

6. Identification of components of the CVR system that meet TSO standards, including the TSO number and any authorized deviations from the TSO requirements;

7. Description of the bulk erasure function;

8. Method of compliance with any required underwater locating device (ULD) in accordance with §§ 23.1457(g)(3) and 25.1457(g)(3);

Note: Pursuant to International Civil Aviation Organization (ICAO) Annex 6, Operation of Aircraft, Appendix 8, Flight Records, Section 1, ULDs attached to CVRs are required to operate at 37.5 kilohertz (kHz). When flying in international airspace, operators should be familiar with ICAO Standards and Recommended Practices (SARPs).

9. Description of structural alterations associated with the installation;

10. A wiring diagram and system schematic that describes all dedicated wires and identifies all interfaces to other installed equipment and systems, including cockpit-mounted area microphones (CAM), summation amplifiers, and control unit;

11. Description of design for automatic switching to area microphone in the event of primary power source loss;

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12. Instructions that would enable an accident investigation authority to obtain or manufacture any special tools or interface equipment required for the retrieval of the recorded information;

13. Details of the procedures to be followed for retrieval of the recorded information from an undamaged recorder;

14. Details of the procedures to be followed for retrieval of the recorded information from any memory device used within the crash-protected memory module removed from a crash-damaged recorder;

15. Detailed information and/or tools necessary to permit data recovery from individual memory chips (or equivalent);

16. Any special procedures related to an aircraft storage program where the CVR/ULD remains installed in the aircraft during storage;

17. Instructions for continued airworthiness (ICA);

18. Physical location of the CVR installation;

Note: The installer must locate and mount CVRs to minimize the probability of container rupture from crash impact and subsequent fire damage to the recorder.

Where duplicate recording systems are installed, such as with two combination CVR/FDR systems, you may install the second system near the cockpit (refer to § 25.1459).

19. Description of the start and stop logic; and

20. Description of the means to synchronize the CVR recording with other flight recorder recordings (e.g., microphone keying).

2.3 Intended Function. The CVR system is an item of installed equipment that must be designed to perform its intended function, as required by § 23.2505, § 25.1301, § 27.1301, or § 29.1301.

2.3.1 Continuous Operation. The CVR system must operate continuously from the use of the checklist before the flight to completion of the flight to the final checklist at the end of flight as specified by § 91.609, § 121.359, § 125.227, § 129.24, or § 135.151.

2.3.2 Record Retention. The operator must retain recorded communication for at least 60 days or, if requested by the Administrator or the Board, for a longer period as required by § 91.609, § 121.359, § 125.227, § 129.24, or § 135.151.

2.3.3 Communication Sources. Pursuant to § 23.1457, § 25.1457, § 27.1457, or § 29.1457, the CVR must record the following communication sources:

1. Voice communications transmitted from or received in the airplane or rotorcraft by radio to include the pilot and second pilot boom, mask, or handheld microphone, headset, or speaker if installed.

2. Voice communications of flight crewmembers on the flight deck using a CAM.

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3. Voice communications of flight crewmembers on the flight deck using the airplane or rotorcraft interphone system.

4. Voice or audio signals identifying navigation or approach aids introduced into a headset or speaker.

5. Voice communications of flight crewmembers using the passenger loudspeaker system and if there is such a system, and if the fourth channel is available, each boom, mask, or handheld microphone, headset, or speaker used at the station for the third and fourth crewmembers; or if the stations are not required or if the signal at such a station is picked up by another channel, each microphone on the flight deck that is used with the passenger loudspeaker system, if its signals are not picked up by another channel.

6. Required data link communication (DLC) as the output signal from the communication unit that translates the signal to usable data when data link is installed.

2.3.3.1 Pursuant to § 23.1457 or § 25.1457, fixed-wing airplanes with CVR systems must record the following sources on separate dedicated channels:

• First pilot station audio;

• Second pilot station audio;

• CAM; and

• Passenger loudspeaker system and any third and fourth crewmember station’s audio.

2.3.3.2 Pursuant to § 27.1457 or § 29.1457, rotorcraft with CVR systems must record the following sources on separate dedicated channels:

• First pilot station audio;

• Second pilot station audio;

• CAM or the continually energized or voice-actuated lip microphone at the first and second pilot stations; and

• Third and fourth crewmember stations, if applicable, and/or each microphone on the flight deck used with the passenger loudspeaker system.

2.3.4 Aircraft Installed Performance. The applicant should install the CVR system in accordance with EUROCAE Document (ED)-112A, Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems, dated September 2013, Chapters 2-5 and I-6.

2.4 Demonstrate Performance. The applicant must demonstrate the CVR system performs as intended pursuant to § 23.2505, § 25.1301, § 27.1301, or § 29.1301. A means to demonstrate this can be found in EUROCAE ED-112A, Chapters 2-5 and I-6.

2-4 EUROCAE ED-112A, Annex I-A, Post Flight Evaluations of Recordings, can be used for postflight evaluation of the flight test recordings.

Note: Using the flight test data, confirm the CVR operates continuously from the use of the checklist before the flight, to the completion of the final checklist at the end of the flight, as required by § 91.609, § 121.359, § 125.227, § 129.24, or § 135.151.

2.5 Equipment. The applicant must present evidence that the equipment is properly manufactured. The following applicable FAA-approved TSOs describe one means of demonstrating manufacturing compliance:

• TSO-C121b, Underwater Locating Devices (Acoustic) (Self-Powered). A ULD manufactured under TSO-C121b, or later revision, is FAA-approved.

• TSO-C123c, Cockpit Voice Recorder Equipment. A CVR meeting the requirements of TSO-C123c, or later revision, is FAA-approved.

• TSO-C155b, Recorder Independent Power Supply (RIPS). If applicable, a RIPS manufactured under TSO-C155b, or later revision, is FAA-approved.

• TSO-C177a, Data Link Recorder Equipment. If applicable, data link recorder (DLR) equipment manufactured under TSO-C177a, or later revision, is FAA-approved.

2.6 Combination CVR/FDR Systems. Operators may install a combination CVR/FDR.

2.6.1 Airplane Requirements. On airplanes that require two separate recorders, a single combination CVR/FDR may not serve as both the required CVR and the required FDR.

An operator may use a combination FDR and CVR system for either the required FDR or CVR, and may install two combination FDR and CVR units in the airplane. The unit designated as the CVR must have an independent power source. Where duplicate recorders are installed, such as with two combination CVR/FDRs, one recorder should have the independent power source located as close as practicable to the CVR and be located near the cockpit. Refer to § 23.1457(d)(5).

2.6.2 Rotorcraft Requirements. On rotorcraft, one combination FDR and CVR unit may be installed to meet the requirement for an FDR and a CVR. Applicants must install the combination FDR and CVR unit such that no single electrical failure external to the recorder can disable both the CVR and the FDR functions.

2.7 DLR.

2.7.1 Compliance With 14 CFR. If a DLR is required to be installed pursuant to the operator’s appropriate operating rules, the DLR must comply with §§ 23.1457(a)(6), 25.1457(a)(6),

27.1457(a)(6), and 29.1457(a)(6). Refer to §§ 91.609(j), 121.359(k), 125.227(i), 129.24, and 135.151(h). In applying these regulations, aircraft are divided into two groups: those manufactured on or after the effective date of the rule and those manufactured before that date.

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2.7.1.1 T hose airplanes or rotorcraft manufactured on or after the effective date identified in the appropriate operating rule must record messages that use the approved message set when both of the following conditions are met:

• T he aircraft is required to have both a CVR and an FDR; and

• The aircraft has DLC equipment installed.

2.7.1.2 Those airplanes or rotorcraft manufactured before the effective date of the rule must record messages that use the approved message set when both of the following conditions are met:

• The aircraft is required to have both a CVR and an FDR; and

• No DLC equipment for the make, model, and series (M/M/S) of the aircraft was approved before the effective date of the rule.

2.7.2 Software Requirements. A DLR may be a standalone line replaceable unit (LRU), a function in a CVR, or combination CVR/FDR. If the CVR includes software, the software should be developed according to RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification, dated December 1, 1992, to at least the software level consistent with the failure condition classification defined in TSO-C123c.

While TSO-C123c requires compliance with RTCA/DO-178B, the FAA published AC 20-115D, Airborne Software Development Assurance Using EUROCAE ED-12() and RTCA DO-178(), on July 21, 2017, encouraging applicants to use RTCA/DO-178C, Software Considerations in Airborne Systems and Equipment Certification, dated December 13, 2011.

2.7.3 Recording Requirements. Data link recordings must be retrievable in a readable format that translates the signal into usable data. Data link recordings should include a date and time stamp to allow the data to be aligned with the CVR and FDR. Refer to § 23.1457, § 25.1457, § 27.1457, or § 29.1457, as applicable, for more information.

2.8 Weight and Balance (W&B). Installation or removal of equipment affects the aircraft W&B. Pursuant to 14 CFR part 43, § 43.5, “no person may approve for return to service any aircraft, airframe, aircraft engine, propeller, or appliance, that has undergone maintenance, preventive maintenance, rebuilding, or alteration unless the maintenance record entry required by § 43.9 or § 43.11, as appropriate, has been made.” If the installation results in changes to the W&B procedures in the flight manual, the operator should submit a flight manual supplement to the responsible Aircraft Certification Service office for approval and must adjust aircraft records to show such change.

2.9 Electrical Load Analysis (ELA). Installation or removal of equipment affects the electrical load to the aircraft power distribution system. A report must show the net change in the electrical load on each affected bus and how the change was computed. The net change to the load carrying capability of the essential bus must not result in interruption or otherwise adversely affect power distributed to other loads on that bus.

Refer to § 25.1351, § 27.1351, or § 29.1351, as applicable, for more information. For

2-6 par t 23 a irplanes certified before August 30, 2017, refer to § 23.1351. For part 23 airplanes certificated after August 30, 2017, refer to §§ 23.2325, 23.2500, 23.2525, and 23.2605.

2.10 Electrical Power Sources. The CVR must receive its operating electrical power from the bus that allows maximum reliability for the CVR system. The CVR should be added to an essential or emergency bus unless the electrical load does not allow it. Refer to § 23.1457, § 25.1457, § 27.1457, or § 29.1457, as applicable, for more information.

2.10.1 Connection to Power Source. The installer should connect the CVR and FDR to power buses that are separate and supplied by independent power sources. If the applicant cannot add the CVR system to the emergency or essential bus, the applicant should provide two separate and independent sources of electrical power for the CVR and FDR.

2.10.2 Power Sources. Separate aircraft power sources are required for installation of a single combination CVR/FDR system. If two combination units are installed and more than one electrical power input is available at each of the combination CVR/FDR units, then connection with a separate and independent electrical power bus is recommended.

2.10.3 Independent Power Source. Depending on the intended operation, see Appendix B for applicability. One CVR or combination CVR/FDR must have an independent power source that provides 10±1 minutes of electrical power to operate both the CVR and the CAM. If a RIPS is used to meet this requirement, then the RIPS must be located as close as practicable to the CVR.

2.11 Circuit Protection Devices. Circuit protection devices must handle anticipated loads for the CVR system. Refer to § 25.1357, § 27.1357, or § 29.1357, as applicable. For part 23 airplanes certificated before August 30, 2017, refer to § 23.1357. For part 23 airplanes certificated after August 30, 2017, refer to §§ 23.2500, 23.2505, 23.2510, and 23.2525.

The circuit breaker (CB) rating, location, and name of CB label should be identified in the ICA and Airplane Flight Manual (AFM) or Rotorcraft Flight Manual (RFM) and supplements.

2.12 Preflight Monitoring. The installation must have an aural or visual means to check the recorder for proper operation. Refer to § 23.1457, § 25.1457, § 27.1457, or § 29.1457, as applicable, for more information.

2.13 Flight Manual Applicability. The operator should review the AFM or RFM and supplements to determine whether they are compatible with the CVR system installation.

If TSO-123c is followed, the operator must provide an approved AFM or RFM Supplement to eliminate incompatibilities. Refer to TSO-C123c, paragraph 5a for more information.

2.14 ICAs as Part of Substantiating Data. The operator must provide ICAs as part of the substantiating data. Under the requirements of § 23.1529, § 25.1529, § 25.1729, § 27.1529, § 29.1529, or 14 CFR part 26, § 26.11 and the latest FAA-published ICA guidance, these instructions must be included as a minimum and be provided to the