electrical power to the required services provided that its air start capability is adequate and may be guaranteed. Where, however, the APU is dependent for its starting current on a battery source which is supplying critical loads, such starting loads may prejudice the time duration of the flight if APU start is not achieved.
(i) It may be necessary, therefore, to include limitations on the number of attempted starts or to provide a separate battery for APU starting, if this method of supplying electrical power is adopted. Consideration should also be given to the equipment, services and duration required prior to the APU generator coming on-line. Common failures which could affect the operation of all engines and the APU
(e.g., fuel supply) should be taken into consideration.
(2) Transmission-driven Generator.
A transmission-driven generator may be utilized to provide an emergency electrical power source, but due consideration should be given to ensuring that the means of bringing the generator into use are not dependent on a source which may have been lost as a result of the original failure.
(i) The continuity of electrical power to those services, which should remain operative without crew action prior to the generator being brought into operation, may necessitate the use of a battery, unless the operation of the emergency power source is automatic and immediate in the event of failure of the normal electrical power generating system.
(3) Pneumatic or Hydraulic Motor Driven Power Source. A pneumatic- or hydraulic-motor-driven electrical power source may be utilized subject to the same constraints on activation as the transmission-driven generator (See 3.4.2(b)).
Care should be taken in ensuring that the operation of the pneumatic or hydraulic system is not prejudiced by faults leading to, or resulting from, the original failure, including the loss of, or inability to restart engines.
653. § 29.1353 (Amendment 29-14) ELECTRICAL EQUIPMENT AND INSTALLATIONS.
a. Explanation.
(1) Electrical equipment, controls, and wiring must be installed so that operation of any one unit or system of units will not adversely affect the simultaneous operation of any other electrical unit or system essential to safe operation.
(2) Results of qualification testing should be available to ensure that the installation of equipment or a system will not result in adverse interference being introduced into the rotorcraft electrical equipment. A good reference for interference testing is the applicable version of Radio Technical Commission of Aeronautics (RTCA) 1014 Par 652
Document No. DO-160, "Environmental Conditions and Test Procedures for Airborne Equipment."
(3) The DO-160 type tests would normally be accomplished by the equipment manufacturer. The airframe manufacturer's test are normally more subjective and are oriented more toward watching for unwanted meter movement, noise in the interphone systems, and so forth. The combination of the equipment manufacturer's tests, supplemented by the airframe manufacturer's installation tests, should be adequate to assure compliance with this regulation.
b. Procedures.
(1) General. Chapter Il of Advisory Circular 43.13-1A, "Acceptable Methods, Techniques, and Practices: Aircraft Inspection and Repair," includes considerable guidance regarding the installation of electrical systems (routing, separation, typing, clamping, j-box installations, etc.). The following areas are overlooked in many cases and special emphasis should be placed on them during the compliance inspection of the rotorcraft:
Feeder wires from the rotorcraft's generators and batteries should be routed separately from utilization system wiring.
(ії) Generator field wiring should be routed separately from generator output wiring. This should begin at the generator and continue to the voltage regulator.
(2) Battery Installation.
As part of the electrical system evaluation, the battery installation should be reviewed to assure the battery is vented and drained. If there is some doubt regarding the ability of the drain to satisfactorily dispose of corrosive fluids, TIA tests should be conducted to resolve the issue. Normally this is done by expelling a dye solution through the drain system during different phases of flight to assure that fluids are drained clear of the rotorcraft. Some aircraft rely on the installation of a sump jar to dispose of corrosive fluids.
(ii) In nickel cadmium batteries are used for engine starts and compliance with § 29.1353(c)(6) is achieved through the use of a temperature monitoring system, the temperature sensor should be located in a position that will most accurately reflect the internal battery temperature without causing adverse effects to the sensor. The location normally used is near the center of the battery. If the sensor is placed between two cells, the indication should be very close to the actual temperature within the cell. If the sensor is placed in a cell strap, there will normally be a period of time just after a heavy current drain (e.g., engine start) when the sensor shows a temperature that is hotter than the actual cell temperature.
Par 653 1015
Other aspects of the battery installation can be resolved by reviewing § 29.1353(c), AC 43.13-1A, and AC 43.13-2A, "Acceptable Methods, Techniques, and Practices Aircraft Alterations."
654. § 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 portions 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.
654A. § 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.
1016 Par 653
655. § 29.1357 CIRCUIT PROTECTIVE DEVICES.
a. Explanation. Circuit protective devices are normally installed to limit the hazardous consequences of overloaded or faulted circuits. These devices are resettable (circuit breakers) or replaceable (tuses) 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 properly an aircraft crew function which cannot be performed by automatic reset circuit breakers. To assure 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) provided that 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 to be essential to some phase of flight or it would not be required. It follows from this that the circuit protective device associated with those systems is generally considered to be essential for safety in flight and should therefore be accessible to the crew in the cockpit. 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.
Where continued safe flight to the destination is considered to be sufficiently assured, Par 655 1017
AC 29-2B 7130/97 certain required circuits have been excepted from being accessible to the crew in the cockpit. Voltmeter and ammeter circuit protective devices are examples of ones that have been excepted. Some utilization systems, although not specifically required by FAR 29, may be required because of the particular design presented for certification.
Circuit protective devices for systems in this category are considered to be required and must be accessible.
(5) The following are considered to be acceptable compliance with the "readily reset" provision of § 29.1357 (d).
(1) 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.
(il) 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) 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 nonrequired 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."
(7) Refer to Paragraph 777 of this advisory circular for specific tests of circuit protection for the total electrical system.
655A. § 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 1018 Par 655
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 systems 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.
656. § 29.1359 ELECTRICAL SYSTEM FIRE AND SMOKE PROTECTION
a. Explanation. This regulation requires 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 fumes on the aircraft cabin occupants should be accounted for.
(2) Wire qualified to MIL-W-25038 is normally used in circuits thatmust be at least fire resistant. Wire qualified to other specifications may also be satistactory;
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 evaluating 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/AUTHORITY has taken no such action, Par 655A 1019
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.
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.
(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.
657. § 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 777 of this AC instead of being made a part of this paragraph.
b. Procedures.
(1) Reference Paragraph 777 of this AC 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.
1020 Par 656
(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.
658.-667. RESERVED.
Par 657 1021 (thru 1031)
AC 29-2B 7130/97 SECTION 37. LIGHTS
668. § 29.1381 INSTRUMENT LIGHTS.
a. Explanation. This section provides 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.
669. § 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 1032 Par 668
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.
670. § 29.1385 POSITION LIGHT SYSTEM INSTALLATION. Refer to AC 20-74, Aircraft Position and Anticollision Light Measurements, July 29, 1971.
671. § 29.1387 (Amendment 29-9) POSITION LIGHT SYSTEM DIHEDRAL ANGLES.
Refer to AC 20-74.
672. § 29.1389 POSITION LIGHT DISTRIBUTION AND INTENSITIES. Refer to AC 20-74.
673. § 29.1391 MINIMUM INTENSITIES IN THE HORIZONTAL PLANE OF FORWARD AND REAR POSITION LIGHTS. Refer to AC 20-74.
674. § 29.1393 MINIMUM INTENSITIES IN ANY VERTICAL PLANE OF FORWARD AND REAR POSITION LIGHTS. Refer to AC 20-74.
675. § 29.1395 MAXIMUM INTENSITIES IN OVERLAPPING BEAMS OF FORWARD AND REAR POSITION LIGHTS. Refer to AC 20-74.
676. § 29.1397 (Amendment 29-7) COLOR SPECIFICATIONS. Refer to AC 20-74.
677. § 29.1399 RIDING LIGHI
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 Par 669 1033
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 621 of this AC.) 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 Publication 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:
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°x Tx D x KD where: I is luminous intensity in candelas under service conditions, T is threshold factor 2 × 107 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.
(3) Solving this formula indicates a minimum intensity of 4.3 candelas is required for this light..
1034 Par 677
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.
678. § 29.1401 (Amendment 29-11) ANTICOLLISION LIGHT SYSTEM.
(1) Certification for night operations requires an approved aviation red anticollision light. Determination of the location and how many anticollision lights are required to satisfy the regulations are tunctions 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 § 29.1401(b) is given in AC 20-30B.
An explanation of the methods used to measure and calculate the light intensity and color required by § 29.1401 (e) are explained in AC 20-74.
(2) The anticollision lights) should be located to obtain the required coverage and to prevent cockpit reflections that would affect the crew's vision. The anticollision 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 29.1401(b) was changed in 1976 to require a red anticollision 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.
679.-688. RESERVED.
Par 677 1035 (thru 1043)