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-I and A-II 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:
(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 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 further 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 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:
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 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 light(s). 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 light(s) 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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SUBPART F - EQUIPMENT
SAFETY EQUIPMENT AC 27.1411 § 27.1411 (Amendment 27-11) SAFETY EQUIPMENT--GENERAL.
a. Explanation.
(1) This section contains requirements for the accessibility and stowage of required safety equipment. Compliance with this section should ensure that:
(i) Locations for stowage of all required safety equipment have been provided.
(ii) Safety equipment is readily accessible to both crewmembers and passengers, as appropriate, during any reasonably probable emergency situation.
(iii) Stowage locations for all required safety equipment will adequately protect such equipment from inadvertent damage during normal operations.
(iv) Safety equipment stowage provisions will protect the equipment from damage during emergency landings when subjected to the inertia loads specified in § 27.561.
(2) It is a frequent practice for the rotorcraft manufacturer to provide the substantiation for only those portions of the ditching requirements relating to aircraft flotation and ditching emergency exits. Completion of the ditching certification to include the safety equipment installation and stowage provisions is then left to the affected operator so that those aspects can best be adopted to the selected cabin interior. In such cases, the “Limitations” section of the Rotorcraft Flight Manual should identify the substantiations yet to be accomplished in order to justify the full ditching approval. The operator (or modifier) performing these final installations is then concerned directly with the details of this paragraph. Any aspects of the basic rotorcraft flotation and emergency exits approval that are not compatible with the modifier’s proposed safety equipment provisions should be resolved between the type certificate holder and the modifier prior to FAA/AUTHORITY approval for ditching. (See paragraphs AC 27.801a(9) and AC 27.1415a(3).)
b. Procedures.
(1) A cockpit evaluation should be conducted to demonstrate that all required emergency safety equipment to be used by the crew will be readily accessible during any probable emergency situation. This evaluation should include, for example, emergency flotation equipment actuation devices, remote liferaft releases, hand fire extinguishers, and protective breathing equipment.
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(2) Stowage provisions for safety equipment shown to be compatible with the vehicle configuration presented for certification should be provided and identified so that:
(i) Equipment is readily accessible regardless of operational configuration.
(ii) Stored equipment is free from inadvertent damage from passengers and handling.
(iii) Stored equipment is adequately restrained to withstand the inertia forces specified in § 27.561(b)(3) without sustaining damage.
(3) Liferaft stowage provisions should be sufficient to accommodate rafts for the maximum number of occupants for which certification for ditching is requested.
(i) Liferafts stowed inside the rotorcraft should be located near the ditching emergency exits so that:
(A) Liferafts are readily accessible and deployment through ditching emergency exits by passengers and crew may be accomplished without unreasonable effort and training.
(B) Deployment of liferafts can be accomplished without damage (i.e., punctures, tears, etc.).
(ii) Liferafts stowed outside of the rotorcraft should have-- (A) A readily accessible deployment device; and (B) A secondary method of deployment near the stowed area.
(iii) Rotorcraft fuselage attachments for the liferaft static lines required by § 27.1415(c) must be provided.
(A) Static line fuselage attachments should not be susceptible to damage when the rotorcraft is subjected to the maximum emergency ditching water entry loads established by § 27.801. (See paragraph AC 27.801b(1).)
(B) Static line fuselage attachments should be structurally adequate to restrain a fully loaded raft of the maximum capacity required for ditching certification.
(C) Liferafts that are remotely or automatically deployed must be attached to the rotorcraft by the required static line after deployment without further action from the crew or passengers.
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(4) Stowage provisions for signaling equipment required by § 27.1415 should be located near a designated ditching emergency exit.
(5) If stowage provisions for life preservers are included in an interior configuration, each life preserver when stowed must be within easy reach of each occupant while seated.
(6) Service experience has shown that following deployment, life rafts are susceptible to damage while in the water adjacent to the helicopter due to projections on the exterior of the helicopter such as antennas, overboard vents, guttering, etc.
Projections likely to cause damage to a deployed life raft should be modified or suitably protected to minimize the likelihood of their causing damage to a deployed life raft.
Relevant maintenance information should also provide procedures for maintaining such protection for rotorcraft equipped with life rafts.
AC 27.1413 § 27.1413 (Amendment 27-25) SAFETY BELTS.
a. Explanation. Design and performance standards are contained in this section.
(1) Each safety belt must be equipped with metal-to-metal latches (Amdt. 27-15).
(2) Belts and belt anchors must sustain without failure ultimate loads as prescribed for each installation.
(3) Seats and berths are included.
(4) Litters, if installed, shall be included.
(5) TSO-C22, Safety Belts, contains acceptable aircraft belt standards. Also, TSO-C114, Torso Restraint Systems, dated March 27, 1987, contains acceptable aircraft standards for compliance to the standard per Amendment 27-25, dated November 13, 1989. In part, the belts shall have a 2-inch nominal width, shall be self-extinguishing per § 25.853(a), and may have a 1,500- or 3,000-pound rated strength.
b. Procedures.
(1) TSO-C22 or TSO-C114 approved seat belts or seat belt/harnesses should be used. The rated load shall not be exceeded. During an interior compliance inspection, the belt should be checked for label, rating, and metal-to-metal latches.
(2) The type design data shall contain an analysis or test results of belts and anchors proving compliance with the strength standards of this section. Fitting factors prescribed in § 27.785 shall be used.
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(3) The use or application of the belts shall be proven in compliance with the standard. The belt rated strength shall not be exceeded by the ultimate load derived from § 27.561(b).
(4) The rated strength of each unique belt may be stated in structural loads or design criteria report and the corresponding maximum ultimate design load listed for ease of comparison.
AC 27.1415 § 27.1415 (Amendment 27-11) DITCHING EQUIPMENT.
a. Explanation.
(1) Emergency flotation and signaling equipment is not required for all rotorcraft overwater operations. However, if such equipment is required by an operating rule
(e.g., § 135.167), the equipment supplied for compliance with the operating rule must meet the requirements of this section.
(2) Compliance with the provisions of § 27.801 for rotorcraft ditching requires compliance with the safety equipment stowage requirements and ditching equipment requirements of §§ 27.1411 and 27.1415, respectively.
(i) Emergency flotation and signaling equipment installed to complete certification for ditching or required by any operating rule must be compatible with the basic rotorcraft configuration presented for ditching certification. It is satisfactory if operating equipment is not incorporated at the time of original type certification of the rotorcraft provided suitable information is included in the “Limitations” section of the Rotorcraft Flight Manual to identify the extent of ditching certification not yet completed.
(ii) When the ditching equipment required by § 27.1415 is being installed by a person other than the applicant who provided the rotorcraft flotation system and ditching emergency exits, special care must be taken to avoid degrading the functioning of the aircraft devices and to make the ditching equipment compatible with them. (See paragraphs AC 27.801a(9) and AC 27.1411a(2).)
b. Procedures.
(1) Liferafts and life preservers used to show compliance with the ditching requirements must be of an approved type. Compliance with the requirements of TSO-C12 for liferafts and TSO-C13 for life preservers will satisfy regulatory requirements for approval of this equipment.
(i) Life Preservers.
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(A) Life preservers should comply with the requirements of the applicable operating regulations (FAR Parts 91, 135, 121, etc.). For extended overwater operations, each life preserver is required by the operating rules to have an approved survivor locator light.
(B) Protective covers for life preservers should be compatible with the TSO requirements under which the basic life preserver was approved.
(ii) Liferafts.
(A) Liferafts are rated during their approval to the number of people that can be carried under normal conditions and the number that can be accommodated in an overload condition. Only the normal rating may be used in relationship to the number of occupants permitted to fly in the rotorcraft.
(B) Each liferaft released automatically or by the pilot must be attached to the rotorcraft by a line to secure the liferaft close to the rotorcraft for occupant egress.
The line should be of adequate strength to restrain the liferaft under any reasonably probable sea state condition but must be designed to release before submerging the empty raft to which it is attached if the rotorcraft sinks.
(iii) Survival Equipment. Approved survival equipment if required by any operating rule must be attached to each liferaft. Provisions for the attachment and stowage of the appropriate survival equipment should be addressed during the ditching equipment segment of the basic ditching certification.
(2) Emergency signaling equipment required by any operating rule must be free from hazard in its operation. Required signaling equipment must be easily accessible to the passengers or crew and should be located near an emergency ditching exit or included in the survival equipment attached to one of the rafts.
AC 27.1419. § 27.1419 (Amendment 27-19) ICE PROTECTION.
a. Background.
(1) In March 1984, the FAA/AUTHORITY for the first time certificated a rotorcraft for flight into known icing conditions. Several other manufacturers are pursuing designs for icing flight capability.
(2) Most rotorcraft icing technology has been developed for military rotorcraft.
As of 1990, the only U.S. military rotorcraft equipped and approved for flight into icing conditions is the UH-60A (Blackhawk). The UH-60A is limited to supercooled cloud conditions where liquid water content (LWC) does not exceed 1.0 gm/m3 and outside air temperature (OAT) is not below -20° C.
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