This appendix establishes an approach to show compliance for non-rechargeable lithium batteries and their installation to the safety objectives listed in this appendix. It is also intended to ensure, as required by 27/29.601 and 27/29.1309, that the installation does not represent a hazard to the rotorcraft and its occupants.
Pursuant to 27/29.601, the design must not have features or details that experience has shown to be hazardous or unreliable.
Pursuant to 27/29.863, provide a means of minimizing the probability of ignition of flammable fluids or vapours that might leak from flammable liquid sources, and the resultant hazards in the event of ignition.
Pursuant to 27/29.1301, ensure each system is appropriate for its intended function, and is labelled and installed according to its limitations and function.
Pursuant to 29.1309, ensure all systems 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.
Pursuant to 27.1309, all systems must perform their intended function under any foreseeable operating conditions, systems must be designed to prevent hazards to a multiengine rotorcraft in the event of a probable malfunction or failure and minimize hazards to a single engine rotorcraft.
Pursuant to 29/27.1353, storage batteries must be designed and installed to maintain safe cell temperatures and pressures that no explosive or toxic gases can accumulate in hazardous quantities, and that corrosive fluids or gases cannot damage surrounding structures or essential systems.
Pursuant to 27/29.1529, requires that Instructions for Airworthiness be prepared that are acceptable to the Authority.
RTCA/DO-227A, Minimum Operations Performance Standards (MOPS) for Non-Rechargeable Lithium Batteries.
AC 29-2C, Certification of Transport Category Rotorcraft.
Eight Safety Objectives are identified as critical for safe installation of non-rechargeable lithium batteries on rotorcrafts. Each non-rechargeable lithium battery installation must show compliance with the following Safety Objectives:
E.1.1 Safety Objective 1: The battery shall be designed to maintain safe cell temperatures and pressures under all foreseeable operating conditions to prevent fire and explosion.
E.1.2 Safety Objective 2: The battery shall be to prevent the occurrence of self-sustaining, uncontrollable increases in temperature or pressure.
E.1.3 Safety Objective 3: The battery shall 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 rotorcraft.
E.1.4 Safety Objective 4: The battery must meet the flammable fluid fire protection requirements of 29.863.
E.1.5 Safety Objective 5: The battery and installation must be designed to prevent corrosive fluids or gases that may escape from damaging surrounding structure or adjacent systems, equipment, or electrical wiring.
E.1.6 Safety Objective 6: The battery and installation must be designed to prevent any hazardous effect on rotorcraft structure or systems caused by the maximum amount of heat generated from any battery or individual cell failure.
E.1.7 Safety Objective 7: The battery and installation must have a failure sensing and warning system to alert the flight crew if a failure affects safe operation of the rotorcraft.
E.1.8 Safety Objective 8: The battery and installation must provide a means for the flight crew to determine the battery charge state (for required battery systems).
Note: A battery 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. A battery may also be an integral component of an end item assembly. The battery supplies energy to the end item. A battery may also be an end item.
The following MOC have been accepted to ensure that the battery meets Safety Objectives 1 through 8 discussed in the paragraphs above. Some failures may still occur due to various factors beyond the control of the battery and battery system OEM; these MOCs are also intended to address the occurrence of these unexpected failures. RTCA/DO-227A provides a MOC acceptable to the DASA for installation of non-rechargeable lithium batteries on rotorcraft. General design and construction requirements necessary to reliably and consistently produce lithium batteries appropriate for installation into the expected rotorcraft environment are found in paragraph 2.1, General Requirements and Design Guidelines. Paragraph 2.2, Functional and Safety Requirements, defines the minimum functional requirements for battery cells, batteries, and end items. Each subparagraph in paragraph 2.2 references a specific test procedure found in paragraph 2.4. Test procedures and evaluation criteria specifically for cells, batteries and end items are outlined in paragraph 2.4 corresponding to each of the functional and safety requirements. Test conditions are defined in paragraph 2.3.
E.2.1 MOC for Safety Objective 1. Show that the individual cells meet the requirements in RTCA/DO-227A, section 2.2.1 by successfully performing the test procedures in section 2.4.1 and judging the test results against the associated evaluation criteria.
E.2.2 MOC for Safety Objective 2. Safety Objective 1 requires that each individual cell within a non-rechargeable lithium battery be designed to maintain safe temperatures and pressures. Safety Objective 2 requires that the battery and end item installation 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. Show that the battery installation meets the requirements in RTCA/DO-227A, sections 2.2.2 Battery Functional and Safety Requirements and 2.2.3 End Item Functional and Safety Requirements. Successfully perform the test procedures in sections 2.4.2 and 2.4.3. Judge the test results against the associated evaluation criteria for successful showing.
E.2.3 Safety Objectives 3 through 6. Use the worst case test data from the MOCs for Safety Objectives 1 and 2 to support demonstrating compliance with SO 3 through 6. The DASA considers that the RTCA/DO-227A, section 2.4.3.2.2 End Item Thermal Runaway Containment Test usually provides these worst case data.
E.2.3.1 MOC for Safety Objective 3. RTCA/DO-227A, appendix A, section A.5 discusses potential gas emissions from batteries and their effects. An acceptable means of complying with Safety Objective 3 includes using the tests required under Safety Objectives 1 and 2 to demonstrate that all emitted gases are contained or vented overboard (i.e., vented outside the rotorcraft) through designed ports. Pursuant to 29.1309, when 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. Safety Objective 3 allows 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.
E.2.3.2 MOC for Safety Objective 4. The amendment level of 25.863 is determined by 14 CFR 21.17 or 21.101, as appropriate. The amendment level is not determined by the issuance or effective date of the special conditions. The Aviation Rulemaking Advisory Committee (ARAC) draft Advisory Circular (AC) 25.863-1, Flammable Fluid Fire Protection gives acceptable guidance on 25.863.
E.2.3.3 MOC for Safety Objective 5. Show that if fluid escapes the battery, 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.
E.2.3.4 MOC for Safety Objective 6. Show that the effects of the heat, and any related effects, from the tests performed under Safety Objectives 1 and 2 do not constitute a hazard to the structure or systems of the rotorcraft. 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 Safety Objective 6.
E.2.4 MOC for Safety Objective 7. Pursuant to 29.1322, Safety Objective 7 requires flight crew alerting for unsafe operating conditions. Flight crew alerting is required when 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 also be considered. The alert must meet the applicable paragraphs of 29.1322. The applicant should refer to the current AC 29-2C for guidance on 29.1322.
E.2.5 MOC for Safety Objective 8. The following are examples of “means” for flight crew or maintenance personnel to determine the battery charge state:
A manually activated system (e.g., push button) that displays the available charge of each battery unit.
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.
Physical access that allows a maintenance person to measure the battery charge state.
The above “means” are acceptable only when the Instructions for Continued Airworthiness (ICA) include 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. After completing all the required test and validation based on the MOC for each safety objectives, provide a summary of all the evaluation criteria and reportable items listed in each test. Compliance to one safety objective does not constitute compliance to any other safety objectives.
Pursuant to part 29, non-rechargeable lithium battery installations should satisfy each of the MOCs identified in this document. The following provides means of compliance and other information on other important part 29 requirements.
E.3.1 System Safety Assessment. Pursuant to 27, 29.1301 and .1309, hazard conditions require specific functionalities and capabilities, and address certain critical failure modes of non-rechargeable lithium batteries and their installations, to date however, in-service experience has shown that non-rechargeable lithium battery thermal/pressure runaway conditions are not extremely improbable. Assuming such failures will occur sometime during the life of the battery installation when demonstrating compliance, periodic maintenance actions or flight crew alerting features such as, an overtemperature warning system may be necessary to allow the flight crew 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, when provided, must meet 27.1322 and 29.1322.
E.3.2. ICA. The ICA should include the following provisions to comply with 27.1529 and 29.1529:
Maintenance requirements to replace each non-rechargeable lithium battery within an interval that will ensure there is sufficient charge to power equipment.
A requirement to only replace non-rechargeable lithium batteries with batteries from the same manufacturer with the same part number or to obtain a new approval for installing a different battery. Refer to the battery Original Equipment Manufacturer’s maintenance manual.
Procedures to ensure that each non-rechargeable lithium battery has not:
Experienced degraded charge retention ability or other damage during storage.
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.
Precautions to prevent mishandling of replacement non-rechargeable lithium batteries prior to their installation which could result in short-circuit or other unintentional damage.
Note: Acceptable procedures for paragraph E.3.2-2 above may include a quality control process for packaging, storing, maintaining and transporting non-rechargeable lithium batteries, including reporting of dropped or damaged batteries.
E.3.3 Uncontained Engine or APU Rotor Failures. Sections 27.903(b), 29.903(d) and 27/29.1309. In general, as part of showing compliance with 27/29.1309, the DASA expects the applicant to demonstrate that a foreseeable event originating from outside of a non-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 compliance with the non-rechargeable lithium battery Safety Objectives, depending on the location of the battery installation, a rotor failure could defeat such safety features. If you propose to install a non-rechargeable lithium battery in a rotor burst zone, you must ensure the means of compliance to the SO’s remains effective considering potential rotor failures that could damage the battery. Regarding compliance to 29.903(d)(1) turbine engine rotor failures, 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 non-rechargeable lithium battery in a rotor burst zone, 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 with the non-rechargeable lithium battery SO’s. Clearly state your method of compliance in your response to this issue paper. Alternatively, the battery is to be located outside of the rotor burst zone.