AC 20-184A Appendix E
• Method of Compliance for Pre-August 2016 SC 4. Appendix D, sections D.3.4, Method of Compliance for SCs 3 – 6 and D.3.6, Method of Compliance for SC 4, provide a method of compliance.
• Method of Compliance for Pre-August 2016 SC 5. Appendix D, sections D.3.4, Method of Compliance for SCs 3 – 6 a nd D.3.7, Method of Compliance for SC 5, provide a method of compliance.
• Method of Compliance for Pre-August 2016 SC 6. Appendix D, sections D.3.4, Method of Compliance for SCs 3 – 6 and D.3.8, Method of Compliance for SC 6, provide a method of compliance.
• Method of Compliance for Pre-August 2016 SC 7. Section D.3.3, Method of Compliance for SCs 1 and 2 demonstrates that rechargeable lithium batteries are designed to prevent overheating and overcharging. Section D.3.11, Method of Compliance for SC 9, provide additional applicable guidance.
• Method of Compliance for Pre-August 2016 SC 8. Appendix D, section D.3.10, Method of Compliance for SC 8, provides applicable guidance.
• Method of Compliance for Pre-August 2016 SC 9. SC 9 contains specific requirements related to ICAs that must be met. Section 25.1529 is another independent, applicable regulation. Section D.4.3, Section 25.1529 Instructions for Continued Airworthiness (ICA), applies to § 25.15 29.
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AC 20-184A Appendix F APPENDIX F. REGULATIONS AND METHOD OF COMPLIANCE FOR RECHARGEABLE
LITHIUM BATTERIES FOR ROTORCRAFT The method of compliance provided in this appendix is to establish an approach to show compliance for rechargeable lithium batteries and their installation on rotorcraft. This AC is also intended to ensure, as required by §§ 27.601, 29.601, 27.1309, 29.1309,
27.1353, and 29.1353, that the installation does not present a hazard to the rotorcraft and its occupants.
F.1 Regulatory Basis From Part 27 at Amendment 27-51 and Part 29 at Amendment
29-59.
F.1.1 Regulations codified at 14 CFR §§ 27.601 and 29.601 require that the design must not have features or details that experience has shown to be hazardous or unreliable.
F.1.2 Regulations codified at 14 CFR §§ 27.863 and 29.863 require a means of minimizing the probability of ignition of flammable fluids or vapors that might leak from flammable liquid sources and the resultant hazards in the event of ignition.
F.1.3 Regulations 27.1301 and 29.1301 require that each system is appropriate for its intended function and is labeled and installed according to its limitations and function.
F.1.4 Regulations 27.1309 and 29.1309 state that required systems must perform their intended function under any foreseeable operating conditions; systems must be designed to prevent hazards to the rotorcraft in the event of a probable malfunction or failure.
F.1.5 Regulations 27.1353 and 29.1353 require in part that energy storage systems must be designed and installed to maintain safe cell temperatures and pressures so that no explosive or toxic gases can accumulate in hazardous quantities, and that corrosive fluids or gases cannot damage surrounding structures or essential systems.
F.1.6 Regulations 27.1529 and 29.1529 require that the ICA be prepared.
F.2 Advisory Circulars.
• AC 27-1B, Certification of Normal Category Rotorcraft.
• AC 29-2C, Certification of Transport Category Rotorcraft.
F.3 Industry Document.
RTCA DO-311A, Minimum Operational Performance Standards for Rechargeable Lithium Batteries and Battery Systems.
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AC 20-184A Appendix F F.4 Part 27 and 29 Regulations.
The following regulations are identified as critical for safe installation of rechargeable lithium batteries. Each rechargeable lithium battery installation must show that the following are met:
F.4.1 Sections 27.1353(a) and 29.1353(a).
Energy storage systems must provide automatic protective features for any conditions that could prevent continued safe flight and landing.
F.4.2 Sections 27.1353(b) and 29.1353(b).
Energy storage systems must not emit any flammable, explosive, or toxic gases, smoke, or fluids that could accumulate in hazardous quantities within the rotorcraft.
F.4.3 Sections 27.1353(c) and 29.1353(c).
Corrosive fluids or gases that escape from the system must not damage surrounding structures, adjacent equipment, or systems necessary for continued safe flight and landing.
F.4.4 Sections 27.1353(d) and 29.1353(d).
The maximum amount of heat and pressure that can be generated during any operation or under any failure condition of the energy storage system or its individual components must not result in any hazardous effect on rotorcraft structure, equipment, or systems necessary for continued safe flight and landing.
F.4.5 Sections 27.1353(e) and 29.1353(e).
Energy storage system installations required for continued safe flight and landing of the rotorcraft must have monitoring features and a means to indicate to the pilot the status of all critical system parameters.
Note: An energy storage system consists of individual battery cell(s), a battery assembly, and any protective monitoring and alerting circuitry or hardware inside or outside of the battery. It may also include vents (when necessary) and packaging. For the purpose of this guidance, a battery and battery system are referred to as a battery.
F.5 Method of Compliance.
The following method of compliance is acceptable to ensure that the battery complies with §§ 27.1353(a) and 29.1353(a) through §§ 27.1353(e) and 29.1353(e) discussed in the paragraphs above.
F.5.1 RTCA DO-311A, Minimum Operational Performance Standards for Rechargeable Lithium Batteries and Battery Systems, section 2.1 General Requirements provides design requirements and guidelines that are pertinent to designing safe batteries and to meeting Part 27 and 29 applicable requirements and the regulations shown in paragraph F.4 above. Section 2.2, Equipment Requirements – Standard Conditions, defines the minimum functional requirements for battery cells, batteries, and end items. Each F-2
AC 20-184A Appendix F subsection in section 2.2 references a specific test procedure found in section 2.4. Test procedures and evaluation criteria specifically for cells, batteries, and end items are outlined in section 2.4 corresponding to each of the functional and safety requirements.
Test conditions are defined in section 2.3. Consider each of these requirements and guidelines when designing cells and batteries.
F.5.2 Sections 27.1353(a) and 29.1353(a) are intended to ensure that the cells and batteries are designed to eliminate the potential for uncontrollable failures. However, a certain number of failures will still occur due to various factors, many of which are beyond the control of the designer. Therefore, these regulations, as a whole, are intended to protect the rotorcraft and its occupants even if a failure occurs.
F.5.3 These regulations are independent of each other. Demonstrating compliance with one of these regulations does not constitute compliance with the other regulations. An acceptable method of compliance for each regulation is as follows:
F.5.4 Method of Compliance for §§ 27.1353(a) and 29.1353(a).
F.5.4.1 Sections 27.1353(a) and 29.1353(a) require that the cell and battery be designed to prevent propagation of a thermal event, such as self-sustained, uncontrollable increases in temperature or pressure from one cell to adjacent cells.
F.5.4.2 Show that the batteries meet the requirements in RTCA DO-311A, sections 2.2, Equipment Requirements – St andard Conditions (which are applicable according to RTCA DO-311A, section 2.4.2) and 2.3 Equipment Requirements – E nvironmental Conditions. Consider that batteries with less than 2 watt-hours of energy that are not button/coin batteries, or do not meet UL 1642, UL 2054, or IEC 62133, to be energy category 2 batteries. Use the test procedures in RTCA DO-311A, section
2.4, Equipment Test Procedures, to show that the requirements of RTCA DO-311A, section 2.2 are met. Note that RTCA DO-311A, table 2-2 provides a test matrix that defines which tests are required for each category of battery, along with the order of the testing.
F.5.4.3 Provide the FAA with the video of the testing conducted for RTCA DO- 311A section 2.4.5.5.
F.5.5 Method of Compliance for §§ 27.1353(b) and 29.1353(b).
F.5.5.1 An acceptable means of complying with §§ 27.1353(b) and 29.1353(b) includes using any tests used to demonstrate compliance with unde r §§
27.1352(a) and 29.1353(a) to demonstrate that all emitted gases are contained or vented overboard (i.e., vented outside the rotorcraft) through designed ports. If the design has ports to vent gases overboard, show that there are means to protect ground personnel from exposure to these gases and to prevent re-ingestion, for example through engine in-take or air F-3
AC 20-184A Appendix F conditioning in-take, in accordance with §§ 27.13 01, 29.1301, 27.1309, and 29.1309. The applicant should refer to the current AC 27-1B and AC 29-2C for guidance on §§ 27.1309 and 29.1309.
F.5.5.2 Sections 27.1353(b) and 29.1353(b) allow explosive and toxic gases to be uncontained and not vented overboard if they do not accumulate in hazardous quantities within the rotorcraft. Consider the gases emitted from not only the cells but also the battery materials (e.g., insulation separators) when demonstrating compliance by this means.
F.5.5.3 While each paragraph of section(s) 27.1352 and 29.1353 needs to be evaluated specifically, it may be possible to use the results of testing conducted for §§ 27.1352(a) and 29.1353(a) for compliance with §§
27.1353(b) and 29.1353(b). Therefore, if there were gases emitted from the end item (RTCA DO 311A, Category C) during the testing of RTCA DO-311A, section 2.4.5.5, i n compliance with §§ 27.1353(a) and
29.1353(a), the emitted gases must be collected and evaluated for the volume and constituents of the gas. This would provide the ability to evaluate the dissipation and hazard level of these emissions in the location in which the end item is installed.
F.5.6 Method of Compliance for §§ 27.1353(c) and 29.1353(c).
Show that if fluid escapes the battery during testing of regulations 27.1353(a) and
29.1353(a), it is not corrosive or it is managed in a way (e.g., contained, isolated, or vented overboard) to protect the surrounding structure and adjacent systems, equipment, and electrical wiring of the rotorcraft.
F.5.7 Method of Compliance for §§ 27.1353(d) and 29.1353(d).
F.5.7.1 Show that the effects of the heat, and any related effects, from the tests performed under §§ 27.1353(a) and 29.1353(a) do not constitute a hazard to the structure or systems of the rotorcraft necessary for operations, maintenance and continued safe flight and landing.
F.5.7.2 If the effects of the heat or any related effects constitute a hazard to the structure or systems of the rotorcraft, design mitigation at the aircraft level may be applied to bring the design into compliance with regulations
27.1353(d) and 29.1353(d).
F.5.8 Method of Compliance for §§ 27.1353(e) and 29.1353(e).
F.5.8.1 Sections 27.1353(e) and 29.1353(e) require flightcrew alerting to monitor features and have a means to indicate to the pilot of critical system parameters, which may otherwise lead to an unsafe operating condition.
Flightcrew alerting is required if a battery installation failure affects continued safe flight and landing. The effect of the battery failure on other systems that perform functions required for safe flight and landing must F-4
AC 20-184A Appendix F also be considered. The alert must meet the applicable paragraphs of §§
27.1301, 29.1301, 27.1309, a nd 29.1309. The applicant should refer to the current AC 27-1B and AC 29-2C for guidance on compliance with §§ 27.1322, 29.1322, 27.1301, 29.1301, 27.1309, a nd 29.1309.
F.5.8.2 The following are examples of means for flightcrew or maintenance personnel to determine the battery charge state, which is a critical system parameter:
1. A manually activated system (e.g., push button) that displays the available charge of each battery unit.
2. An automatic system that records the available charge of each battery unit on an appropriate interval and makes it available to maintenance personnel before the next flight.
3. Physical access that allows a maintenance person to measure the battery charge state.
Note: The above means are acceptable only if the ICA includes a requirement for a person to check the battery charge state within an interval that will ensure sufficient charge for the entire flight, considering the worst-case scenario, and to replace the battery when the charge is not sufficient.
F.5.8.3 After completing all the required tests and validation, based on the method of compliance for each regulation, provide a summary of all the evaluation criteria and reportable items listed in each test.
F.5.9 Method of Compliance for Very Small Rechargeable Lithium Batteries Less Than 2 Watt-Hours.
Compliance with UL 1642, UL 2054, or IEC 62133 is an acceptable method of compliance to show §§ 27.1353(a) and 29.1353(a) through §§ 27.1352(e) and
29.1353(e) are met for very small button/coin rechargeable lithium batteries installations with less than 2 watt-hours of energy.
F.5.10 Additional Part 27 and 29 Compliance.
Rechargeable lithium battery installations must satisfy each means of compliance identified in this AC and all applicable Part 27 and 29 requirements. The following provides methods of compliance and other information related to compliance with Part 27 a nd 29 requirements.
F.5.10.1 System Safety Assessment.
Although these hazard conditions require specific functionalities and capabilities and address certain critical failure modes of rechargeable lithium batteries and their installations, the applicant must also meet the requirements of §§ 27.1301, 29.1301, 27.1309, 29.1309, 27.1353, and
29.1353. To date, in-service experience has shown that rechargeable F-5
AC 2 0-184A Appendix F lithium battery thermal/pressure runaway conditions are not extremely improbable. Assume such failures could occur sometime during the life of the battery installation when demonstrating compliance with §§ 27.1309 and 29.1309. Application of §§ 27.1309 and 29.1309 may result in required periodic maintenance actions or flightcrew alerting features. For example, an over-temperature warning system may be necessary to allow the flightcrew to manage potentially unsafe system operating conditions.
Provide rationale for alerting requirements (or for why an alert is not needed) in the system safety assessment of the battery installations to demonstrate compliance with §§ 27.1309 and 29.1309. Such alerts, if provided, must meet §§ 27.1322 and 29.1322.
F.5.10.2 The ICA should include the following provisions to comply with §§ 27.1529 a nd 29.1529:
1. Maintenance requirements to replace each rechargeable lithium battery within an interval or monitoring based on state of health that will ensure there is sufficient charge to power equipment.
2. A requirement to only replace rechargeable lithium batteries with batteries from the same manufacturer with the same part number or to obtain a new FAA approval for installing a different battery. Refer to the battery Original Equipment Manufacturer’s maintenance manual.
3. Procedures to ensure that each rechargeable lithium battery has not:
(a) Experienced degraded charge retention ability or other damage during storage.
(b) Been damaged from environmental or physical impacts such as mechanical shock, vibration, heat, and possible abuses encountered during storage, transportation prior to their installation or maintenance activities on or around them.
4. Precautions to prevent mishandling of replacement rechargeable lithium batteries prior to their installation which could result in shortcircuit or other unintentional damage.
Note: Acceptable procedures for paragraph F.5.10.2(3) above may include a quality control process for packaging, storing, maintaining, and transporting rechargeable lithium batteries, including reporting of dropped or damaged batteries.
F.5.10.3 Uncontained Engine or APU Rotor Failures: § 29.1309.
As part of showing compliance with § 29.1309, the FAA expects the applicant to demonstrate that a foreseeable event originating from outside of a rechargeable lithium battery, such as an uncontained rotor burst, will not compromise continued safe flight and landing. While you may use failsafe design features that encase and safely vent the hazardous by products of a failure originated from within the battery to show F-6
AC 20-184 A Appendix F compliance with regulations applicable to rechargeable lithium battery systems, depending on the location of the battery installation, a rotor failure could defeat such safety features. If you propose to install a rechargeable lithium battery in a rotor burst zone, then you must ensure the means of compliance with the regulations remains effective, considering potential rotor failures that could damage the battery.
F.5.10.4 Turbine Engine Rotor Failures: § 29.903(d)(1).
AC 20-128A provides guidance on fragmentation characteristics, and the boundaries of the locations in which applicants are expected to evaluate the effects of impact damage, following an uncontained rotor burst. If you propose to install a rechargeable lithium battery in a rotor burst zone, then you must assess the rotor-burst-induced damage to the battery in your plan for showing compliance with § 29.903(d)(1), in conjunction with complying to regulations applicable to the rechargeable lithium battery.
Clearly state your method of compliance in your response to this section of the AC. Alternatively, the battery must be located outside of the rotor burst zone.
F.5.11 Hazard Mitigations for Large Battery System Thermal Runaway Conditions.
Note: Due to the significance of technical and regulatory issues, coordinate as soon as possible with the FAA.
F.5.11.1 Aircraft requiring high-capacity batteries may increase the severity level and adverse effects resulting from a battery thermal runaway condition, or any other hazards. As stated earlier, using RTCA DO-311A, including articles approved under TSO-C179b, is an accepted approach for addressing the thermal runaway aspects of rechargeable lithium battery installations. All applicable airworthiness regulations must be addressed and complied with. RTCA DO-311A and TSO-C179b, provide a testing standard, and article-level approval that requires additional integration and mitigation strategies to fully comply with the applicable airworthiness regulations on the rotorcraft.
F.5.11.2 In addition, the FAA outlines guidance in F.5.11.3 to address verification aspects of lithium battery thermal runaway conditions for the RTCA DO- 311A section 2.4.5.5. All other tests within RTCA DO-311A are applicable as stated in the industry consensus standard.
F.5.11.3 Battery Thermal Runaway Containment Test (RTCA DO-311A, section 2.4.5.5).
Note: Coordinate as soon as possible with the FAA on the proposed method of compliance for this section.
F.5.11.3.1 RTCA DO-311A, section 2.4.5.5 describes the test methods for battery thermal runaway containment that are designed to force the entire battery F-7
AC 2 0-184A Appendix F into a thermal runaway state. This may not be feasible for very large highcapacity systems. To address the feasibility of very large high-capacity battery system testing, this section of the AC defines a module or sub-pack as a battery system divided into smaller configurations to help in testing and validating the safety implication of the battery system. The battery and battery system can be designed into several smaller modules or sub-packs.
Each module has an assembly of cells electrically connected and enclosed in a single enclosure. Each sub-pack has an assembly of electrically connected modules that is enclosed by a single enclosure. The venting design of the sub-pack, module, and cells need to be considered in the mitigation strategy.
F.5.11.3.2 To successfully comply with the requirement of the RTCA DO-311A section 2.4.5.5 test, it is acceptable to use a modularized/sub-pack battery system design.
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AC 20-184A Appendix G APPENDIX G. INSTALLATION OF RECHARGEABLE LITHIUM BATTERIES FOR SMALL
AIRPLANES G.1 Applicability.
G.1.1 Regulations applicable to installing rechargeable lithium batteries that provide power to small airplanes are §§ 23.2005, 23.2010, 23.2325(g), 23.2410, 23.2500, 23.2505,
23.2510, 23.2525, 23.2605, a nd 23.1529, a ppendix A, at amendment 23-64.
G.1.2 The applicant must meet the current requirements of P art 23 at amendment 23-64 in the areas of change for the rechargeable lithium battery installation, and may use means and methods in this AC on certification projects2 with an original certification basis prior to amendment 23-64, so long as they are not contrary to any special conditions already part of the certification basis.
G.1.3 This appendix does not address compliance with applicable crashworthiness and survivable emergency landing requirements with respect to the rechargeable lithium battery.
G.2 Means of Compliance with Safety Objectives.
The applicant must comply with the following SOs, including all other applicable airworthiness regulations, w hen using the means of compliance in this AC for the installation of rechargeable lithium batteries.
G.2.1 SO 1: Be designed to maintain safe cell temperatures and pressures under all foreseeable operating conditions to prevent fire and explosion.
G.2.2 SO 2: Be designed to prevent the occurrence of self-sustaining, uncontrollable increases in temperature or pressure, and automatically control the charge rate of each cell to protect against adverse operating conditions, such as cell imbalance, back charging, overcharging, and ove rheating.
G.2.3 SO 3: Not emit explosive or toxic gases, either in normal operation or as a result of its failure, that may accumulate in hazardous quantities within the airplane.
G.2.4 SO 4: Meet the requirements of § 23. 2325(g) regarding areas where flammable fluids or vapors might escape by leakage.
G.2.5 SO 5: Not damage surrounding structure or adjacent systems, equipment, components, or electrical wiring from corrosive or any other fluids or gases that may escape in such a way as to cause a major or more-severe failure condition.
2 Including TCs, STCs, ATCs, and ASTCs.
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AC 20-184A Appendix G G.2.6 SO 6: Have provisions to prevent any hazardous effect on airplane structure or systems caused by the maximum amount of heat it can generate due to any failure of it or its individual cells.
G.2.7 SO 7: Have a failure sensing and warning system to alert the flightcrew if its failure affects safe operation of the airplane.
G.2.8 SO 8: Have a monitoring and warning feature that alerts the flightcrew when its charge state falls below acceptable levels if its function is required for safe operation of the airplane.
G.2.9 SO 9: Have a means to disconnect from its charging source in the event of an overtemperature condition, cell failure, or battery failure.
G.3 Method of Compliance with Safety Objectives.
G.3.1 RTCA DO-311A provides data used to demonstrate that rechargeable lithium battery installations meet the means of compliance SOs when using this AC for compliance.
G.3.2 RTCA DO-311A, s ection 2.1, General Requirements, provides design requirements and guidelines that are pertinent to designing safe batteries and meeting Part 23 requirements and the means of compliance SOs. Consider each of these requirements and guidelines when designing cells and batteries.
G.3.3 RTCA DO-311A, sections 1.4, 1.5, 1.6, a nd 2.1 provide guidelines and general requirements that are pertinent to designing and installing safe lithium batteries on aircraft.
G.3.4 SOs 1 and 2 are intended to ensure that the cells and battery are designed to eliminate the potential for uncontrollable failures. However, a certain number of failures will still occur due to various factors beyond the control of the designer. Therefore, the means of compliance SOs, as a whole, are intended to protect the airplane and its occupants if failure occurs.
G.3.5 The following method of compliance must be used to comply with the means of compliance in G.2 a bove. Means of compliance SOs are independent of each other.
Demonstrating compliance with one of these SOs does not constitute compliance with the other SOs.
G.3.5.1 SO 1: Designed to maintain safe cell temperatures and pressures under all foreseeable operating conditions to prevent fire and explosion.
Method of Compliance with SO 1:
1. Show that batteries meet the requirements in RTCA DO-311A, sections 2.2, Equipment Requirements – St andard Conditions (which are applicable according to section 2.4.2) and section 2.3, Equipment Requirements – E nvironmental Conditions.
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AC 2 0-184A Appendix G
2. Use the test procedures in section 2.4, Equipment Test Procedures, to show that the requirements of section 2.2 are met.
G.3.5.2 SO 2: Designed to prevent the occurrence of self-sustaining, uncontrollable increases in temperature or pressure, and automatically control the charge rate of each cell to protect against adverse operating conditions, such as cell imbalance, back charging, overcharging, and overheating.
Method of Compliance with SO 2:
1. SO 2 addresses the same issues for the entire battery as SO 1 for the individual cell. The battery must be designed to prevent propagation of a thermal event due to any operational or fault conditions, such as selfsustained, uncontrollable increases in temperature or pressure.
2. RTCA DO-311A, section 2.4.2, table 2-2, provides a test matrix that defines which tests are required for each category of battery, along with the order of the testing.
3. Provide the FAA with the video of the testing conducted for RTCA DO-311A, s ection 2.4.5.5.
G.3.5.3 SO 3: Not emit explosive or toxic gases, either in normal operation or as a result of its failure, that may accumulate in hazardous quantities within the airplane.
Method of Compliance with SO 3:
1. RTCA DO-311A, section 3.2.1, Hazardous Battery Emissions, discusses potential gas emissions from batteries and their effects. All emitted gases must be contained or vented overboard (i.e., vented outside the airplane) through designed ports.
2. SO 3 does allow explosive and toxic gases to be uncontained and not vented overboard if they do not accumulate in hazardous quantities within the airplane. Consider the gases emitted from not only the cells but also the battery materials (e.g., insulation separators). Provide substantiation to this requirement in terms of analysis and test results.
Use the test results of SO 1 and SO 2 for SO 3.
3. An acceptable means of complying with SO 3 includes using the tests required under SO 1 and SO 2 to demonstrate that all emitted gases are contained or vented overboard (i.e., vented outside the aircraft) through designed vent ports. If the design has ports to vent gases overboard, show that there are means to protect ground personnel from exposure to these gases and to prevent re-ingestion, for example through engine in-take or air conditioning in-take, in accordance with § 23.2510.
4. If there were gases emitted from the end item under RTCA DO 311A Category C during the testing of RTCA DO-311A, s ection 2.4.5.5, i n G-3