complying with Objective 3 include using the tests required by the MOC for Objectives 1, 2 and 7 to demonstrate that all emitted gasses are contained or vented overboard through designed ports. Objective 3 does allow explosive and toxic gases to be uncontained and not vented overboard if they do not accumulate in hazardous quantities within the rotorcraft. If you choose to use the test data to demonstrate compliance by this means, explain how you will demonstrate that hazardous quantities of gases will not accumulate within the rotorcraft. If your design will have ports to vent gases overboard, ensure there is a means to protect ground personnel from exposure to these gases.
iii. MOC for Objective 4: Section AC 27.863 of this guidance, subparagraph (c), provides an acceptable method of compliance for flammable fluids.
iv. MOC for Objective 5:
(a) 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) that protects the surrounding structure and adjacent systems, equipment, and electrical wiring.
(b) Any failure of the battery includes, but is not limited to, internal and external short circuit. See the tests listed in the MOC for Objectives 1, 2, and 7 for Failure Conditions that are evaluated.
V. MOC for Objective 6:
(a) Force a cell in the battery into thermal runaway by conducting the RTCA Document DO-347, section 2.3.15, Thermal Runaway Containment Test.
Perform step e. of test method 2.3.15.1 in lieu of steps c. and d. when conducting this test.
(b) Show that the effects of the heat and any related effects 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 Objective 6.
vi. MOC for Objective 8: A well designed disconnection system will function during the tests required by the MOC for Objectives 1, 2, and 7, except for the test in RTCA Document DO-347, section 2.3.9, where the protection is already disabled.
This is one of the means of preventing the Failure Conditions discussed in the Evaluation Criteria sections of RTCA Document DO-347 for these tests. Confirm the battery automatically disconnects from its discharging circuit during these tests.
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vil. MOC for Objective 9: Objective 9 specifies flight crew alerting if the failure of a battery installation, in itself or in relation to a system that performs an aircraft-level function, could result in "unsafe system operating conditions." The alert should comply with the applicable color requirements in § 27.1322. The applicant should refer to Section AC 27.1322 for an acceptable method of compliance.
vili. MOC for Objective 10: The following are examples of "means" for flight crew or maintenance personnel to determine the battery charge state:
(a) A manually activated system (e.g., push button) that displays the available charge of each battery unit.
(b) 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.
(c) Physical access that allows a maintenance person to measure the battery charge state.
3. The MOCs for Objectives 1 through 10 are only acceptable for required functions if ICAs include a check of the battery charge state within an interval that will ensure sufficient charge for each flight considering the worst case scenario and replacement of the battery when the charge is not sufficient.
4. MOC for Very Small Non-Rechargeable Lithium Batteries:
An acceptable MOC for Objectives 1 through 8 for non-rechargeable lithium battery installations that have less than 2 watt-hours of energy is showing these batteries meet Underwriters Laboratories (UL) 1642 or UL 2054.
(ix) Part 27 Compliance. Non-rechargeable lithium battery installations should satisfy each of the MOCs identified in this guidance to comply with all applicable part 27 requirements. The following provides means of compliance and other information on some part 27 requirements:
(A) System Safety Assessment. Although these hazard conditions require specific functionalities and capabilities and address certain critical failure modes of nonrechargeable lithium batteries and their installations, the applicant must also meet the requirements of § § 27.1301 and 27.1309. To date, in-service experience has shown that non-rechargeable 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. Application of Page F - 62.11
6/23/23 AC 27-1B, Chg 9 § 27.1309(b) and (c) may result in required periodic maintenance actions or flight crew alerting features. For example, an over-temperature 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(c). Such alerts, if provided, must comply with § 27.1322.
(B) The ICA should include the following provisions to comply with § 27.1529:
1. Maintenance requirements to replace each non-rechargeable lithium battery within an interval that will ensure there is sufficient charge to power equipment.
2. 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 FAA approval for installing a different battery. Refer to the battery Original Equipment Manufacturer's maintenance manual.
3. Procedures to ensure that each non-rechargeable lithium battery has not:
i. Experienced degraded charge retention ability or other damage during storage.
ii. 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.
ill. Precautions to prevent mishandling of replacement nonrechargeable lithium batteries prior to their installation that could result in short-circuit or other unintentional damage.
Note: Acceptable procedures for paragraphs b(2) (ix)(B)3.i. and b(2)(ix)(B)3.ii. may include a quality control process for packaging, storing, maintaining, and transporting non-rechargeable lithium batteries, including reporting of dropped or damaged batteries.
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AC 27-1B, Chg 4 3/31/2014 AC 27.1357. § 27.1357 (Amendment 27-13) CIRCUIT PROTECTIVE DEVICES.
a. Explanation. Circuit protective devices are normally installed to limit the hazardous consequences of overloaded or faulted electrical circuits. These devices are resettable (circuit breakers) or replaceable (fuses) to permit the crew to restore service when nuisance trips occur or when the abnormal circuit condition can be corrected in flight.
b. Procedures.
(1) The circuit protective devices for systems essential to safety in flight should not be tripped by faults in other circuits.
(i) Systems that are essential to safety in flight are generally those systems that are required to show compliance with the regulations. These essential systems include the basic electrical system, the distribution system, and many electrical utilization systems.
(ii) An electrical utilization system is a system of electrical equipment, devices, and connected wiring using electrical energy to perform a specific aircraft function.
(ili) The specific utilization systems, which are necessary to maintain controlled flight and land safely, will vary with the type of rotorcraft and with the nature of operations. Examples of systems that may be essential are basic flight instruments, minimum navigation equipment, minimum radio communications, and flight control systems.
(2) Automatic reset circuit breakers, which automatically reset themselves, should not be used as circuit protective devices. If an abnormal circuit condition cannot be corrected in flight, the decision to restore power to the circuit should result from a careful analysis by the flightcrew and cannot be performed by automatic reset circuit breakers. To ensure crew supervision over the reset operation, circuit protective Page F - 62.13
devices should be designed to require a manual operation to restore service after tripping. Circuit breakers must be designed such that the tripping mechanism cannot be overridden by the operating control. These are known as the "trip free" type.
(3) This section requires protective devices for circuits essential to safety in flight to be accessible to the flight crew in the cockpit. These devices should be also readily accessible to the flight crew in the event it becomes necessary to manage smoke caused by an electrical failure. Their accessibility should also permit the flight crew to easily determine if they are in the "tripped" position prior to flight. Again, this generally applies to systems required for compliance as discussed above. If continued safe flight to the destination is sufficiently assured, certain required circuits have been excepted from this accessibility. Voltmeter and ammeter circuit protective devices are examples of ones that have been excepted. Some utilization systems, although not specifically required by part 27, may be required for the particular design to be certified.
Circuit protective devices for these systems should be accessible. The following are considered acceptable compliance with the "readily reset" provision of this guidance:
(i) For operation by a single pilot with seat belt and shoulder harness normally adjusted, the pilot should be able to identify and reset or replace the opened circuit protector while flying the rotorcraft. Circuit protection should not be located aft of a vertical plane passing left to right (laterally) through the pilot's body.
(ii) For a crew of two, it is satisfactory for one crewmember to move his seat and loosen his shoulder harness to identify and reset or replace the circuit protective device. It is not satisfactory for one of the crewmembers to leave his seat to reset or replace the circuit protective device.
(4) A switch is a device intended for regular use to open or close a circuit. A circuit breaker is a device that protects a circuit by opening automatically at a predetermined current overload. Systems should be designed such that the primary means to remove or reset the power supply in normal operations is by means of a switch. The use of a circuit breaker for such normal operations is unacceptable, as it is not being used for its intended function.
Note: A switch-rated circuit breaker may be used for this function if it can be shown to be suitable for the number of switch cycles expected to be performed during the service life of the system.
(5) The spare fuse requirement applies only to fuses protecting systems required to show compliance with the regulations. Spare provisions need not be made for non-required convenience type installations, although it is encouraged. The spare fuses should be stored in a location readily accessible to the crew. For spare fuses not directly visible to the crew, location information should be provided. One acceptable location is on the fuse panel in a holder without wire terminations. The spare fuse should be identified "spare" with the fuse rating.
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AC 27-1B, Chg 4 3/31/2014
(6) Passive circuit protection has been utilized to a limited degree in some designs. To accommodate special installation problems, unprotected wire runs of up to 2 feet have been accepted in a few instances when associated with detailed specific installation data and regular periodic inspections. Specific installation data would normally include information such as routing requirements, clamp locations, requirement for conduit, etc. Electrical master junction boxes usually rely to some degree on passive circuit protection against short circuits on distribution bars. This reliance is normally supported by considerations such as careful layout to minimize the possibility of shorts from loose objects, extensive use of nonconductive materials, terminal covers for relays, etc. Periodic inspections are also normally required. It is desirable to install junction boxes so loose objects will tend to fall away from internal circuitry. Also, careful consideration should be given to flammability characteristics when selecting a nonconductive material.
AC 27.1361. § 27.1361 MASTER SWITCH.
a. Explanation. This paragraph provides for a master switch to allow for a quick disconnect of electric power sources. This provision was intended to minimize the probability of electrical power providing an ignition source during a crash.
b. Procedures.
(1) It has been determined that bypassing the master switch with small load circuits may not significantly increase the probability of electrical ignition of fuel.
Therefore, it is permissible to allow live circuits as described in paragraph (b) of this section.
(2) The pilot should be able to readily identify and operate the master switch from his normal crew position with seat belt and shoulder harness normally adjusted.
The master switch and switch positions should be labeled. The labels should be readily recognized under all certificated flight conditions.
(3) Designs that include multiple power sources may include a "master switch arrangement" instead of a "master switch." This is done to minimize the possibility of a single failure resulting in a total loss of electrical power.
(4) In addition to carefully evaluating the functional aspects of an installation, the malfunction aspects must also be considered as required by § 27.1309. Normally, the installation is protected against inadvertent actuation of the function.
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AC 27.1365. § 27.1365 ELECTRIC CABLES.
a. Explanation. The FAA does not have a wire standard and, in general, relies on military specifications. Where a military specification does not exist, manufacturers' specifications, along with appropriate qualification test data, have been accepted.
b. Procedures.
(1) Chapter 11 of Advisory Circular 43.13-1A, "Acceptable Methods, Techniques and Practices: Aircraft Inspection and Repair," contains a listing of wiring that has been accepted for aircraft installations.
(2) In many instances, references to a basic specification are not adequate since several configurations may exist, and reference to a supplemental specification sheet will also be necessary.
(3) Where wire with thin wall insulation (thickness of at least 10.5 mils.) has been used, some problems can occur if special precautions are not taken when the wire is stamped for identification. The areas of concern are temperature, pressure, and dwell time of the stamp.
(4) Some additional types included in Tables A-l and A-ll of MIL-W-5088H, Appendix A, have also been evaluated and accepted for civil applications. Use of a specific type of wiring selected from this listing should be coordinated with FAA engineering personnel.
(5) Wire insulated with KAPTON® polyimide film manufactured to MIL-W-81381A, has been used in aeronautical products with varying degrees of success. The U.S. Navy had such a bad service history with KAPTON® insulated interconnect wire in aircraft that in the mid-1980s the U.S. Navy no longer allows the use of KAPTON® insulated wire. U.S. Army policy also bans the use of KAPTON® wire in their rotorcraft. Although the FAA has taken no such action, the use of KAPTON® insulated wire requires very special handling. The following areas should be observed when utilizing KAPTON® insulated wire:
The instructions in the KAPTON® wire "Handling Manual" should be strictly followed. This manual may be obtained from E.I. Du Pont de Nemours and Company, Polymer Products Department, Industrial Film Division, Wilmington, Delaware 19898.
(ii) Use in special wind and moisture problem (SWAMP) areas, such as wheel wells, usually requires additional protection for the cable bundles.
(ili) The wire should not be exposed to a combination of either high stress (U.V. or physical) in the presence of water, high humidity, or high PH factor liquids.
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AC 27-1B, Chg 4 3/31/2014
(iv) The stiffness and permanent set (memory) of KAPTON® may cause chafing in unrestrained bundles or where KAPTON® insulated wire is bundled with wires of other insulation types.
(v) Care should be exercised in the stripping, stamping, and terminating of KAPTON® insulated wires.
NOTE: KAPTON® is a registered trademark of E.I. Du Pont de Nemours and Company.
(6) Compliance to the flame resistance requirement should be shown by testing in accordance with FAR 25, Appendix F, Part 1, paragraph (b)(7) for the sixty-degree burn test. FAR 25, Appendix F contains test procedures and pass-fail criteria for this requirement.
AC 27.1367. § 27.1367 SWITCHES.
a. Explanation. Qualification data that are available from the switch manufacturer should provide information regarding contact ratings and environmental limitations.
b. Procedures.
(1) Contact ratings are normally provided by the switch manufacturer. If the particular application is not specifically addressed by the switch manufacturer, additional information is available in Chapter 11, Section 2 of Advisory Circular 43.13-1A, "Acceptable Methods, Techniques and Practices: Aircraft Inspection and Repair."
(2) The rule requires all switches to be accessible.
(i) For operation by a single pilot with seat belt and shoulder harness normally adjusted, the pilot should be able to identify and operate essential switches while flying the rotorcraft. Essential system switches should be located forward of a vertical plane passing left to right (laterally) through the pilot's body.
(ii) For a crew of two, switches for essential systems can be turther back and beyond the reach of the pilot if readily identifiable and accessible to the other pilot or crewmember.
(3) This paragraph requires labeling of all switches. Each switch should be labeled for the circuit controlled, and each switch position should also be labeled.
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SUBPART F - EQUIPMENT LIGHTS AC 27.1381. § 27.1381 INSTRUMENT LIGHTS.
a. Explanation. This section provides minimum performance standards for the instrument lighting system. Section 27.1309(b) is used to evaluate the malfunction aspects of the system. If appropriate, § 27.1309(a) is used to evaluate the equipment under appropriate environmental considerations.
b. Procedures.
(1) The overall instrument lighting system should be designed and installed such that single failures that occur will not result in the loss of both primary and secondary (backup) lighting for any instrument or area of the cockpit. In some instances, the system is divided such that the controls for the pilot's panel are separate from the copilot's panel and both of these are separate from the center panel. The ideal is to divide the system such that the impact of single failures will be minimized.
(2) Secondary (backup) instrument lighting should be provided, and this is accomplished in some instances by eyebrow lights. A system that provides general cockpit lighting from a source in the aft area of the cockpit is normally not acceptable since normal positioning and movement of the crew will block this type of light.
(3) The standard does not specify any color requirements for instrument lighting. White is normally provided. The color provided should ensure that the color coding of the instruments is readily identifiable.
(4) The final installed system should be evaluated by a flight test pilot. An actual night flight should be conducted for initial certification of an aircraft. In some instances the vibration characteristics and other flight-induced factors have been demonstrated to seriously affect the pilot's ability to see in the cockpit environment at night. Evaluations following modifications may be conducted with a darkened cockpit on the ground. It should be verified that direct rays are shielded from the pilot's eyes, and that objectionable reflections do not exist. The pilot should also assume failures of various controls, electrical busses, etc., to account for all appropriate failures.
AC 27.1383. § 27.1383 LANDING LIGHTS.
a. Explanation. This section provides minimum performance standards for the installation and normal operation of the landing lights. Certification to this standard is all that is required for approval of the rotorcraft; however, the different operating rules should also be reviewed since they may contain additional requirements. The malfunction considerations are based on the provisions of § 27.1309(b).
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b. Procedures.
(1) The performance requirements of this standard are normally evaluated by a flight test pilot, and usually are included in the Type Inspection Authorization as part of the evaluation to be conducted at night.
(2) The installation of the landing light unit(s) should be very carefully evaluated. Many of the units provided are stowed until needed and then driven to their operating position by an electric motor. If this type of light unit is provided, the possibility of its contact with fuel fumes should be considered. Installations that have this problem normally require the use of light units qualified as explosion proof. The installation should also be reviewed to determine if a single failure can cause the light to be on in the stowed position. If the light can be on, the potential for overheat or fire in the adjacent area should be considered.
AC 27.1385. § 27.1385 POSITION LIGHT SYSTEM INSTALLATION. Refer to Advisory Circular 20-74, "Aircraft Position and Anticollision Light Measurements.
AC 27.1387. § 27.1387 (Amendment 27-7) POSITION LIGHT SYSTEM DIHEDRAL ANGLES. Refer to Advisory Circular 20-74.
AC 27.1389. § 27.1389 POSITION LIGHT DISTRIBUTION AND INTENSITIES.
Refer to Advisory Circular 20-74.
AC 27.1391. § 27.1391 MINIMUM INTENSITIES IN THE HORIZONTAL PLANE OF FORWARD AND REAR POSITION LIGHTS. Refer to Advisory Circular 20-74.
AC 27.1393. § 27.1393 MINIMUM INTENSITIES IN ANY VERTICAL PLANE OF FORWARD AND REAR POSITION LIGHTS. Refer to Advisory Circular 20-74.
AC 27.1395. § 27.1395 MAXIMUM INTENSITIES IN OVERLAPPING BEAMS OF FORWARD AND REAR POSITION LIGHTS. Refer to Advisory Circular 20-74.
AC 27.1397. § 27.1397 (Amendment 27-6) COLOR SPECIFICATIONS. Refer to Advisory Circular 20-74.
AC 27.1399. § 27.1399 (Amendment 27-2) RIDING LIGHT.
a. Explanation. The riding light is an amphibious operation requirement. The function of this light is to make the rotorcraft visible at night to other vessels when the rotorcraft has landed on water. A very important point which should be remembered is Page F - 68
that when a rotorcraft has landed on the water and is not in flight, it is considered a vessel in accordance with the United States Coast Guard (USCG) navigation rules (Inland Navigation Rules Act of 1980). If water operations are contemplated, one should acquire the USCG Navigation Rules, COMDTINST M16672.2A, which are for sale from Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.
b. Procedures. A white light should be installed in a position where it will show the maximum unbroken light for a horizontal arc of 360° around the rotorcraft. If possible, this light should not be obscured by sectors of more than 6°. The light should be installed to meet the malfunction requirements of § 27.1309(b). (Reference paragraph AC 27.1309.) For the purpose of this light, the following definition found in the Inland Navigation Rules, 33 CFR 84.13, Color specification of lights, and 33 CFR 84.15, Intensity of lights, applies:
(1) The chromaticity of white lights shall conform to the following standards, which lie within the boundaries of the area of the diagram specified for each color by the Interparated by reference it is pubican CEl No.22 (1C-161,1975, anals avaich is from the Illumination Engineering Society, 345 East 47th Street, New York, NY 10017.
It is also available for inspection at the Office of the Federal Register, Room 8401, 1100 L Street NW., Washington, D.C. 20408.
(2) The boundaries of the area for white are given by indicating the corner coordinates, which are as follows:
0.525 0.525 0.452 0.310 0.310 0.443
0.382 0.440 0.440 0.348 0.283 0.382 and 33 CFR 84.15 defines the required luminosity to be visible on a clear night for 2 nautical miles. The minimum luminosity of the light is given by the formula:
1 = 3.43 × 10° xT x D' x K° where: I is luminous intensity in candelas under service conditions, T is threshold factor 2 x 107 lux,
• is range of visibility (luminous range) of the light in nautical miles, and K is atmospheric transmissivity. For prescribed lights the value of K shall be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.
(3) Solving this formula indicates a minimum intensity of 4.3 candelas is required for this light.
NOTE: The FAR and the USCG navigation rules may be satisfied by an externally hung lights). One method of compliance would be to use USCG approved all-around lights which are of the appropriate luminosity and externally hung.
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AC 27.1401. § 27.1401 (Amendment 27-10) ANTI-COLLISION LIGHT SYSTEM.
a. Certification for night operations requires an approved aviation red anti-collision light. Determination of the location and how many anti-collision lights are required to satisfy the regulations are functions of aircraft shape and the ability to obtain the required area coverage and light intensity. A detailed explanation of how to calculate the measured area coverage required by § 27.1401(b) is given in AC 20-30B. An explanation of the methods used to measure and calculate the light intensity and color required by § 27.1401 (e) are explained in AC 20-74.
b. The anti-collision lights) should be located to obtain the required coverage and to prevent cockpit reflections that would affect the crew's vision. The anti-collision lights are required to be red to reduce cockpit reflections and objectionable effect of rotor blade strobing. During the period of August 11, 1971, through February 4, 1976, white lights were permitted by the rules; however, white lights resulted in undesirable cockpit reflections at night and in close proximity to clouds. For these reasons, white lights are not considered to be satisfactory in all operating conditions. Section 27.1401(b) was changed in 1976 to require a red anti-collision light. White lights have been approved for installation on rotorcraft when they were installed in addition to the required red lights, if an independent control for the white light was provided that allowed the pilot to eliminate any adverse cockpit reflections.
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