(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 §§ 29.1301 and 29.1309. 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 § 29.1309. Application of § 29.1309(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 § 29.1309(c). Such alerts, if provided, must comply with § 29.1322.
(B) The ICA should include the following provisions to comply with § 29.1529:
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.
iii. 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- Page F - 78.12
rechargeable lithium batteries, including reporting of dropped or damaged batteries.
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AC 29.1355. § 29.1355 (Amendment 29-14) DISTRIBUTION SYSTEM.
a. Explanation. None.
b. Procedures.
(1) When determining compliance with the portion of the rule that concerns supplying essential circuits in the event of reasonably probable faults or open circuits, the effects of tripped circuit breakers or blown fuses should be considered.
(2) Various means may be used to ensure an energy supply. Examples include duplicate electrical equipment, throwover switching, and multichannel or loop circuits separately routed.
(3) Essential load circuits are those circuits whose functioning is required to show regulatory compliance with the certification basis. In addition to those circuits specifically required by the regulations, this definition also includes those circuits required by general rules such as § 29.1309.
(4) An independent power source includes not only the electrical power source
(e.g., generator) but other items such as a regulator or a reverse current cutout that are necessary to make the electrical power source deliver power to a distribution bus.
When a regulatory requirement exists for two independent power sources, the required items should not be shared.
(5) Electrical system faults may occur that will result in a portion of the system (feeders, buses, etc.) being lost. Where por tions of the electrical system may be switched from one power source to another to compensate for a fault, it is important that the transfer action not result in the loss of the replacement source. Circuit design should be such as to assure this will not happen.
AC 29.1355A. § 29.1355 (Amendment 29-24) DISTRIBUTION SYSTEM.
a. Explanation. Amendment 29-24 provides clarification for availability of the remaining electrical power source after a failure of one of two independent power sources.
b. Procedures. All of the policy material pertaining to this section remains in effect with the addition that an automatic or manually selectable means is required to maintain operation of the equipment or system for which the two independent power sources were required.
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AC 29-2C, Chg 4 5/1/2014 AC 29.1357. § 29.1357 (Amendment 29-24) CIRCUIT PROTECTIVE DEVICES.
a. Explanation. Circuit protective dev ices are normally installed to limit the hazardous consequences of overloaded or faulted 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) Overvoltage protection is specifically required for category A rotorcraft. For category B rotorcraft, the possible types of operation should be considered in combination with the presence of an overvoltage condition in the generating system.
The regulatory requirement to support this assumption is § 29.1309(b). If the presence of an overvoltage condition in the electrical system will not cause a hazard to the rotorcraft, the electrical system could be approved for category B without overvoltage protection. If a hazardous condition will result from the overvoltage condition, then overvoltage protection must be provided.
(2) Automatic reset circuit breakers, which automatically reset themselves periodically, should not be applied as circuit protective devices. If an abnormal circuit condition cannot be corrected in flight, the decision to restore power to the circuit involves a careful analysis of the flight situation. The necessity of the circuit for continued safe flight should be weighed against the hazards of resetting on a possibly faulted circuit. Such an evaluation is proper ly an aircraft crew function that cannot be performed by automatic reset circuit breakers. To ensure crew supervision over the reset operation, circuit protective devices should be of such design that a manual operation is required to restore service after tripping. Circuit breakers must be designed such that the tripping mechanism cannot be overridden by the operating control, and these circuit breakers are known as the “trip free” type.
(3) Automatic reset circuit breakers may be used as integral protectors for electrical equipment (e.g., thermal cutouts) if circuit protection is also installed to protect the cable to the equipment.
(4) If the installation of a system is required as a prerequisite to showing compliance with the regulations, it is generally considered essential to some phase of flight or it would not be required. It follows that the circuit protective devices associated with those systems are generally considered essential to safety in flight and should therefore 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. This includes the basic electrical system, the distribution system, and utilization systems that are required. Some examples of required utilization systems are those specified by §§ 29.1303, 29.1305, 29.1307, 29.1381, 29.1383, 29.1385, 29.1401, and 29.1431.
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Where continued safe flight to the destination is considered to be sufficiently assured, certain required circuits have been excepted from being accessible to the crew in the cockpit. Voltmeter and ammeter circuit protec tive devices are examples of ones that have been excepted. Some utilization systems, although not specifically required by part 29, may be required because of the particular design presented for certification.
Circuit protective devices for systems in this category are considered required and must be accessible.
(5) The following are considered acceptable compliance with the “readily reset” provision of § 29.1357(d).
(i) For a crew of two pilots, it is satisfactory for one of the crewmembers to move his seat and loosen his shoulder harness in order to properly identify and reset or replace a circuit protective device. It is not satisfactory for one of the crewmembers to leave his crew station to reset the circuit protective device.
(ii) For a single pilot situation, with the seat belt and shoulder harness normally adjusted, the circuit protective device location should allow for identification of the opened circuit protector and reset capability while the pilot is flying the rotorcraft.
(6) 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.
(7) If fuses are used, there should be spare fuses for use in flight equal to at least 50 percent of the number of fuses for each rating required for complete circuit protection. This only applies to fuses used to protect systems that are 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 where they are readily accessible to the crew. If not directly visible to the crew, information regarding location of the spare fuses should be provided. One acceptable location is on the fuse panel in a holder with no wire terminations and identified “spare” with the “size.”
(8) Refer to MG 2 of this AC for specific tests of circuit protection for the total electrical system.
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AC 29-2C, Chg 4 5/1/2014 AC 29.1357A. § 29.1357 (Amendment 29-24) CIRCUIT PROTECTIVE DEVICES.
a. Explanation. Amendment 29-24 to the regulations provides the requirements for automatic reset circuit breakers and expands the requirements for disconnecting power sources and transmission equipment to include other malfunctions besides overvoltage. The overvoltage protection requirements are extended to both Category A and Category B rotorcraft. Clarification was added to the requirement for each essential load to have individual circuit protection.
b. Procedures.
(1) All of the policy material pertaining to this section remains in effect except that protection from hazardous overvoltage and other malfunctions that would damage equipment should be provided for both Category A and Category B rotorcraft. The protective sensing/switching devices should disconnect the overvoltage or other malfunctions with sufficient speed to prevent user equipment damage.
(2) In addition, each essential load should have individual circuit protection.
This generally means each electrical power consuming device should have individual protection. An exception may be simple syst ems with multiple lights in a single lighting system which would, in most cases, require only one circuit protective device. The decision of whether one or more protective devices are required, is based on how independent each of the loads should be to one another and what the penalty would be if one load faulted and deprived the remaining loads of electrical power.
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AC 29.1359. § 29.1359 ELECTRICAL SYSTEM FIRE AND SMOKE PROTECTION.
a. Explanation. This regulation requi res that all electrical system components meet the applicable fire and smoke protection provisions of §§ 29.831 and 29.863, and further requires that certain items in designated fire zones must be at least fire resistant.
This regulation becomes very significant when failure conditions are considered, and in accordance with the provisions of § 29.831 “reasonably probable failures” must be considered when assuring compliance.
b. Procedures.
(1) When selecting a type of wire, the burning characteristics of that wire are important. Both composition and quantity of resultant smoke and fumes should be considered. The impact of the smoke and fu mes on the aircraft cabin occupants should be accounted for.
(2) Wire qualified to MIL-W-25038 is normally used in circuits that “must be at least fire resistant.” Wire qualified to ot her specifications may also be satisfactory;
however, the provisions of the other specifications should be compared to the provisions of MIL-W-25038 to assure the critical areas are not compromised.
(3) Electrical connectors that are located in a designated fire zone and are used in emergency procedures should be at least fire resistant and capable of maintaining the integrity of the circuit. When evaluati ng these connectors, careful attention should be directed to the entire connector (the contact, the insert, and the shell).
(4) 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-1980’s the Navy no longer allowed the use of KAPTON® insulated wire. Although the FAA/AUTH ORITY 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:
(i) 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.
(iii) 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 29-2C, Chg 4 5/1/2014
(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.
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AC 29.1363. § 29.1363 ELECTRICAL SYSTEMS TESTS.
a. Explanation. Most of this rule is self-explanatory. Since other regulatory paragraphs also contain requirements regarding functioning and malfunctioning of the electrical system, a recommended test procedure has been included in paragraph AC 29 MG 2 instead of being made a part of this paragraph.
b. Procedures.
(1) Reference paragraph AC 29 MG 2 for a recommended test procedure.
(2) When simulating the electrical characteristics of the distribution system wiring, emphasis should be placed on duplicating the type, gage, and length of the wiring being evaluated. As much as possible, cable bundling and grounding considerations should also be duplicated.
(3) Most laboratory test connected loads would normally be in the form of load banks rather than providing the actual aircraft system. If load banks are used during laboratory testing, additional consideration should be given to these loads when an actual aircraft installation is available.
(4) Limited aircraft testing should also be accomplished to verify that the response of the laboratory drives does adequately simulate the response of the rotorcraft engines under normal and malfunction conditions.
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SUBPART F - EQUIPMENT LIGHTS AC 29.1381. § 29.1381 INSTRUMENT LIGHTS.
a. Explanation. This section provi des minimum performance standards for the instrument lighting system. Section 29.1309( b) is used to evaluate the malfunction aspects of the system. If appropriate, § 29. 1309(a) is used to evaluate the equipment under 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.
(5) In some instances manufacturers have provided high intensity instrument lighting systems as an option associated with IFR approvals. If provided, this capability should be included in the overall evaluation of the instrument lighting system.
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AC 29.1383. § 29.1383 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 § 29.1309(b).
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 overheating or fire in the adjacent area should be considered.
AC 29.1385. § 29.1385 POSITION LIGHT SYSTEM INSTALLATION. Refer to AC 20-74, Aircraft Position and Anticollision Light Measurements, July 29, 1971.
AC 29.1387. § 29.1387 (Amendment 29-9) POSITION LIGHT SYSTEM DIHEDRAL ANGLES. Refer to AC 20-74.
AC 29.1389. § 29.1389 POSITION LIGHT DISTRIBUTION AND INTENSITIES. Refer to AC 20-74.
AC 29.1391. § 29.1391 MINIMUM INTENSITIES IN THE HORIZONTAL PLANE OF FORWARD AND REAR POSITION LIGHTS. Refer to AC 20 -74.
AC 29.1393. § 29.1393 MINIMUM INTENSITIES IN ANY VERTICAL PLANE OF FORWARD AND REAR POSITION LIGHTS. Refer to AC 20-74.
AC 29.1395. § 29.1395 MAXIMUM INTENSITIES IN OVERLAPPING BEAMS OF FORWARD AND REAR POSITION LIGHTS. Refer to AC 20 -74.
AC 29.1397. § 29.1397 (Amendment 29-7) COLOR SPECIFICATIONS. Refer to AC 20-74.
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AC 29.1399. § 29.1399 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 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 § 29.1309(b) (reference paragraph AC 29.1309). 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 International Commission on Illumination (CIE), in the “Colors of Light Signals,” which is incorporated by reference. It is Publ ication CIE No. 2.2 (TC-1.6), 1975, and is available 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:
X 0.525 0.525 0.452 0.310 0.310 0.443 Y 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:
l = 3.43 x 106 x T x D2 x K-D where: l is luminous intensity in candelas under service conditions, T is threshold factor 2 x 10-7 lux, D is range of visibility (luminous range) of the light in nautical miles, and K is atmospheric transmissivity. For the prescribed lights the value of K shall be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.
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