AC 29.812. § 29.812 (Amendment 29-24) EMERGENCY LIGHTING.
a. Explanation. Section 29.812 was added by Amendment 24. This change unified the requirements for an emergency lighting system into a single paragraph and required these systems only for Category A rotorcraft. The purpose of this change was to afford passengers flying in Transport Category A rotorcraft the same level of safety in an emergency evacuation at night as passengers flying in transport category airplanes.
b. Procedures. This paragraph is quite similar to the emergency lighting system required for Part 25 airplanes. The exception is there are no requirements in this paragraph for floor proximity emergency escape path markings. The following items should be considered in the design of emergency lighting systems:
(1) There is a requirement for two controls of the system. One of these controls is located in the cabin, where it can be operated by a flight crew member or a passenger. The other control is located in the cockpit. These switches must have an “ON,” “OFF,” and “ARMED” position. These switches should operate independently of each other, and any other systems in the rotorcraft. The emergency lights must become lighted or remain lighted if the switch is either turned on, or the switch is in the armed position and there is an interruption of the rotorcraft electrical power supply.
Inertia switches should not be used to satisfy this requirement.
(2) Sharing of light bulbs with the normal cabin lighting is acceptable provided there is sufficient isolation of the emergency lighting system from the normal cabin lighting circuits. No single failure of the shared portion should render the emergency lighting system inoperative.
(3) The luminosity tests of the emergency lighting system should be accomplished with the emergency exits open.
AC 29.813. § 29.813 (Amendment 29-12) EMERGENCY EXIT ACCESS.
a. Explanation. Paragraph (a) of § 29.813 prescribes design details for passageways, both between passenger compartments and for access to Type I and II emergency exits, should they be provided. Such passageways are not made mandatory by § 29.813 although most larger rotorcraft have used them. Some utility or “wide-body” rotorcraft may have open areas between the crew area (pilots) and passenger area (cabin). These configurations may have lateral seating arrangements providing access to emergency exits of Type I or II size, even though they may not be required by § 29.807(b). These designs may not have a main aisle.
(1) Paragraph (c) of this standard concerns access to Type III and Type IV exits. Although “passageways” with explicit requirements are not required for Type III and Type IV exits, “access from each aisle to each Type III and Type IV exit” is required.
Page D - 106
(2) For exits whose thresholds are more than 6 feet above the ground, additional space adjacent to the exit is required to allow room for a crewmember to assist passengers with the descent device such as an escape slide or rope noted in § 29.809(f).
(3) In addition to requiring passageways and crewmember space adjacent to exits over 6 feet above the ground, this standard does not allow obstructions in the projected opening of Type III or Type IV emergency exits for one seat width from the exit, except as noted. For passenger seating configurations of 19 or less, minor obstructions into the projection of the exit are allowed only if “compensating factors to maintain the effectiveness of the exit” are provided.
b. Procedures.
(1) The provision for unobstructed passageways, at least 20 inches wide as specified, is straightforward for medium or large cabins with a main aisle and a typical rectangular floor plan. Care should be taken to assure that seats (with lateral or fore-and-aft movement) or galleys (with doors or drawers) are not installed so that they can encroach upon the required passageway. Design features such as stops in seat tracks, seat back mechanisms, stops in galley door (or drawer) mechanisms may be required to assure that unobstructed passageways are provided.
(2) The requirement (added by Amendment 29-12) that “access from each aisle to each Type III and Type IV exit” be provided may add design features to the interior of many typical compact interiors of medium-size rotorcraft. Rotorcraft with emergency exits located in either hinged or sliding doors and having passenger area encroachment or protrusions by compartments for fuel cells, gear boxes, etc., may require special design features to assure that passengers seated to one side or one area of the cabin have “access” to all Type III or Type IV exits on the same or other side of the rotorcraft.
The cabin must not be separated into compartments or partitioned. For example, fold down seat back mechanisms may be required for compact cabin configurations having only lateral aisles rather than longitudinal aisles and having Type III or Type IV exits located on each side of the cabin at the end of the lateral seat row or rows.
(3) The space adjacent to an exit that requires a crewmember to assist passengers with descent devices must be large enough to prevent the crewmember from becoming an obstruction in access to the exit. Twenty inches of access must be maintained.
(4) Minor obstructions are allowed in the projected opening of Type III or Type IV exits (for 19 or less passenger seat configurations) if “compensating factors to maintain the effectiveness of the exit” are provided. Compensating factors may include such design features as larger than required exit opening, additional exits beyond the minimum number required, or steps or other assist features which facilitate egress through the exit with the obstruction. Test or analysis may be required to prove the effectiveness of the compensating feature.
Page D - 107
AC 29.815. § 29.815 (Amendment 29-12) MAIN AISLE WIDTH
a. Explanation. Main aisle widths are specified in the following table:
Minimum main passenger aisle width Passenger seating capacity Less than 25 inches 25 inches and more from floor from floor Inches Inches 10 or less---------------------------------- 12* 15 11 through 19---------------------------- 12 20 20 or more-------------------------------- 15 20 *A narrower wi dth not less than 9 inches may be approved when substantiated by tests found necessary by the Administrator.
b. Procedures.
(1) Provide the specified aisle minimum width where a longitudinal main aisle is provided in the type design.
(2) Historically, certain rotorcraft with short, wide cabins were initially designed without a longitudinal main aisle for military and cargo use, but were later fitted and approved for civil passenger configuration. These craft generally have 19 or less passenger seats and have either (1) outboard facing passenger seats, (2) a limited number of lateral rows with fold down seats/seat backs, or (3) a combination of lateral and longitudinal rows with and without main aisles to facilitate entrance and egress.
Page D - 108
AC 29.831. § 29.831 VENTILATION.
a. Explanation.
(1) This rule specifies minimum ventilation requirements for each passenger and crew compartment. The minimum requirement for fresh air in the crew compartment is that amount that will allow the crew to accomplish their duties without undue discomfort or fatigue which shall be at least 10 ft3/m per crewmember. The passenger and crew compartments are also required to be free from harmful or hazardous concentrations of gases or vapors. Specifically for carbon monoxide, the concentration may not exceed 1 part in 20,000 parts of air during forward flight. Failure conditions must also be considered when applying this rule.
(2) This rule becomes more significant when engine bleed air is used for conditioning of the passenger and crew compartments’ air. Certain data are necessary in order to properly analyze the bleed air provided under normal and malfunction conditions. The airframe manufacturer can normally look to the engine manufacturer for a specification of the maximum amount of air that can be extracted and the temperature of the extracted air. The engine manufacturer also normally provides a failure analysis that identifies ways the bleed air can be contaminated and the associated oil flow rates under each failure condition. The oil manufacturers are in a position to provide information regarding breakdown of the oil under different temperature conditions and the impact of that breakdown on the quality of the air being provided to the passenger and crew compartments.
b. Procedures.
(1) The passenger and crew compartments should be initially analyzed to ensure that at least 10 ft3/m per crewmember of ventilation air is being provided. The emphasis has been placed on forward flight and, “air scoops” have been one way of showing compliance with this rule. Most installations also include blowers; however, they are normally provided primarily for defogging the windshields, and a secondary benefit is some circulation during ground or hover operation. In addition, the flight test crew should be asked to do a qualitative evaluation to ensure the amount of ventilation air actually provided meets the requirement for the crew to be able to accomplish their duties without undue discomfort or fatigue. In addition, the ventilation devices provided should not excessively increase the noise level in the cockpit. Compliance with the first requirement of § 29.831(a) can therefore be shown by an analysis showing the existence of at least 10 ft3/m per crewmember, and a report from the flight test crew indicating that the amount actually provided is satisfactory.
(2) The passenger and crew compartment should be monitored under normal operating conditions for the presence of carbon monoxide. A carbon monoxide test kit is normally used for this evaluation. Air is monitored around outlets and different combinations of windows closed/open, heat off/on, air-conditioner off/on, etc., are checked to ensure all conditions are evaluated.
Page D - 109
(3) When engine bleed air is used to condition the passenger and crew compartments’ air, it should be initially substantiated that under normal operation, the amount of air being extracted does not exceed the limit established by the engine manufacturer. To accomplish this, determine the flight condition that will give the maximum bleed air flow through the flow limiter (venturi). The flow calculations should use this maximum flow condition and should also be made using the maximum tolerance diameter of the venturi throat.
(4) The engine bleed air should also be evaluated under malfunction conditions to determine a worst-case air contamination condition. (A typical worst -case malfunction is for an oil seal to fail in the engine that allows the engine oil supply to be introduced into the airflow.) With information regarding the contaminant, flow rate calculations can be made to predict the contamination levels that will be reached in the passenger and crew compartments and also the associated time duration of passenger and crew exposure. The severity of the exposure to the contaminated air is related to the temperature of the oil when it is introduced into the airflow. For example, synthetic base oils manufactured to MIL-L-7808 or MIL-L-23699 begin to break down into toxic components when the temperature exceeds 300° C (572° F). The oil manufacturers have evaluated this problem and should be in a position to provide data regarding the amount and type of toxic components to be expected, and the effect of introducing those components into the passenger and crew compartments. Therefore, from information supplied by the engine manufacturer, the worst-case air contamination condition can be calculated, and this can be compared with results of the oil manufacturers’ tests to determine if the concentrations are harmful or hazardous.
AC 29.833. § 29.833 HEATERS.
a. Explanation. This standard provides that each combustion heater must be approved. The standard contains no provisions regarding functioning of the system, environmental considerations, or malfunctions, therefore, the provisions of §§ 29.1301 and 29.1309 should be used to evaluate those aspects of an installation. The provisions of § 29.831, ventilation, should also be considered, as well as § 29.859, concerning combustion heater fire protection.
b. Procedures.
(1) Technical Standard Order, TSO-C20, was issued June 15, 1949, and amended on April 16, 1951, and concerns Combustion Heaters. If a heater chosen for installation has been qualified to the provisions of TSO-C20, it is considered to be approved. If a unit is not qualified to TSO -C20, a qualification program for the heater itself should be established with FAA/AUTHORITY certification engineers participating in the program as early as possible. The program should be based on the provisions of the TSO.
(2) The TSO refers to the SAE Aeronautical Standard, AS 143B, which specifies certain additional devices, design features, air supply considerations, performance tests, safety controls, environmental considerations, and so forth.
Page D - 110
Consideration of all of the provisions of the aeronautical standard should result in an approved unit; however, it will not necessarily result in a satisfactory installation. For environmental considerations, it should be possible to specify an environmental spectrum more suitable to rotorcraft by referencing the latest version of Document No. RTCA/DO-160, Environmental Conditions and Test Procedures for Airborne Equipment, rather than AS 143B. Other specifications may also be satisfactory.
(3) The installation evaluation should consider functioning of the system based on the provisions of § 29.1301. Section 29.1309(a) is the regulatory basis for consideration of environmental conditions, and the expected environmental conditions resulting from the installation should be compared to those specified in the TSO. If the two are not compatible, additional environmental considerations are appropriate. The provisions of § 29.1309(b) should be used to evaluate the possible malfunctions of the installed system, and this evaluation should be documented in a fault analysis. The provisions of § 29.831 should be considered since certain standards of ventilation air quality under normal and malfunction conditions are specified. Additionally the provisions of § 29.859 should also be considered.
Page D - 111
SUBPART D - DESIGN AND CONSTRUCTION
FIRE PROTECTION AC 29.851. § 29.851 FIRE EXTINGUISHERS.
a. Explanation.
(1) The standard concerns objective performance criteria for both handheld fire extinguishers in the crew and passenger compartments and built-in fire extinguisher systems if the system is required.
(2) Section 29.853(e) and (f) dictate the quantity and general location of the handheld fire extinguishers.
(3) Section 29.855(d) contains standards for cargo/baggage compartments.
(4) Sections 29.1541 and 29.1561 concern durable and conspicuous markings and placards for location and operation or use of the equipment.
(5) The rotorcraft flight manual should contain appropriate information as well.
(6) Advisory Circular 20-42C, Handheld Fire Extinguishers for use in Aircraft, provides an acceptable means of compliance with the standard.
b. Procedures.
(1) Advisory Circular 20-42C provides valuable information to select the type and size of the handheld extinguishers.
(2) The type design data shall contain appropriate information. One location should be used (recommended) for the crew compartment. Several locations may be selected to allow for evaluation and approval of several extinguishers and their locations in the passenger compartment.
(3) During a compliance inspection of a complete interior, the installation of required and optional extinguishers shall be checked for compliance.
(4) Whenever an extinguisher is installed, even though not required by § 29.853(f), it shall also comply with the standards.
Page D - 112
AC 29.853. § 29.853 (Amendment 29-23) COMPARTMENT INTERIORS.
a. Explanation.
(1) Interior materials and components, windows, linings, etc., must meet certain flammability standards as set forth in Amendment 29-17. The rule refers to Part 25, Appendix F (Amendment 25-32), for procedures. Flight Standards Service Release No. 453 contained acceptable flammability standards for specified interior materials prior to adoption of Amendment 29-17.
(2) Smoking may be permitted with use of self-contained removable ashtrays as specified in § 29.853(c).
(3) Fire resistant waste containers may be used as specified.
(4) Hand fire extinguishers are required for flight crewmembers and passengers as specified. Section 29.851 and AC 20- 42C, Hand Fire Extinguishers for use in Aircraft, dated March 7, 1984, contain standards for the extinguishers.
Section 29.1561(b) concerns identification and operating information signs for the safety equipment, and § 29.1411 concerns accessibility of the equipment.
(5) Amendment 29-23 adopted new flammability requirements for passenger seat and seat back cushions. Section 29.853(b) was added to require tests of “fire blocking” features of the cushions including upholstery materials. The rule refers to Part II, Appendix F, FAR Part 25 or an equivalent for the test procedures and test specimen requirements. Appendix F to Part 25, effective November 26, 1984, is the correct reference.
b. Procedures.
(1) With adoption of Amendment 29-17, materials subject to the flammability standards were significantly expanded. Acrylic windows and signs and transparencies were, for example, included. The rules list the materials and components subject to the flammability standards and refer to Appendix F of FAR Part 25 for the test procedures.
Specific burn chambers are also required for the tests. See paragraph b(5) below for flame application time and reference to Appendix F.
(2) A placard prohibiting smoking at all times may be used if ashtrays are not provided. If ashtrays are provided, the installation must have an inner fire resistant liner to close off the ashtray cavity or receptacle when the ashtray is removed. An illuminated sign or signs must be used if prescribed. Each crewmember must be able to control illumination of the sign.
(3) Fire resistant waste containers must have self-closing lids, such as a spring-loaded lid. If a removable container is installed in the receptacle, it must meet the same fire resistant standards as the receptacle. The receptacle must not have any openings outside the galley or an opening into the rotorcraft structure. An opening may Page D - 113
allow accumulation of trash and may allow flames and smoke to go throughout the rotorcraft in case of fire.
(4) A fire extinguisher must be adjacent to crew seats and must be readily accessible to the crew (§§ 29.1411 and 29.853(e)). The extinguisher should be accessible to the crewmember while he is seated. Fire extinguishers are also required in the passenger compartment for seven or more passengers. If one passenger is allowed in the left forward crew seat and six passengers are allowed in the passenger compartment, an extinguisher is not required for the passenger compartment. The extinguisher specified in § 29.853(e) should be located, whenever possible, so that it is visible and convenient to the passengers. If the passenger compartment extinguisher or extinguishers (§ 29.853(f)) are not visible to the passengers when seated, locating signs will be required. See § 29.1561(b).
(5) FAR Part 25, Appendix F, Part 1, established in Amendment 25-32 (effective May 1, 1972) contains flammability test procedures that must be used when complying with § 29.853 of Amendment 29-17. Appendix F refers to sections of FAR Part 25 that do not coincide with sections of the FAR Part 29. To preclude confusion the following statements should be used to develop company test procedures that will provide for compliance with § 29.853.
(i) Section 29.853(a)(1) materials are tested (vertically) to procedures in Appendix F, paragraph (d), and the flame must be applied for 60 seconds and then may be removed.
(ii) Section 29.853(a)(2) materials are tested (vertically) to procedures in Appendix F, paragraph (d), and the flame must be applied for 12 seconds and then may be removed.
(iii) Section 29.853(a)(3) and (4) materials are tested (horizontally) to procedures in Appendix F, paragraph (e), and the flame must be applied for 15 seconds and then may be removed.
(iv) Appendix F, paragraph (h) contains criteria for burn length measurement.
(v) Appendix F, paragraph (f) contains a procedure that does not apply to FAR Part 29, certification rules through Amendment 29-19.
(vi) Appendix F, paragraphs (a), (b), and (c) contain appropriate test procedures. It is noted § 29.853(a)(4) materials are equivalent to the materials specified in § 25.853(b-3).
(vii) Electrical wire and cable materials are tested in accordance with FAR 25, Appendix F, paragraph (g). (Refer to §§ 29.1351(d)(3), 29.831, and 29.863, and possibly special conditions for some rotorcraft.)
Page D - 114
(6) AC 23-2, Flammability Tests, dated August 20, 1984, pertains to small airplanes and their materials. This AC includes information from Flight Standards Service Release No. 453 and may be useful in preparing a test proposal for flash-resistant, flame-resistant, fire-resistant, and fireproof materials. FAR Part 1 contains a further definition of these four terms.
(7) The “fire blocking layer” features of the seat cushions must be tested as prescribed in Appendix F, Part II, Part 25. Specific test equipment and devices are prescribed. AC No. 25.853-1, Flammability Requirements for Aircraft Seat Cushions, dated September 17, 1986, provides guidance material for demonstrating compliance with the seat cushion flammability standards.
AC 29.855. § 29.855 (Amendment 29-24) CARGO AND BAGGAGE COMPARTMENTS.
a. Explanation. This section contains standards for accessible and inaccessible compartments. The rotorcraft should be able to contain a fire until it is detected and extinguished or until a safe landing and evacuation are accomplished. The cabin may be used as a cargo compartment for rotorcraft used for carriage of cargo only.
Protective breathing equipment is required (§ 29.1439) for an appropriate crewmember or crewmembers when a compartment is accessible in flight. The rule does not provide for classification of cargo compartments. Reference is made to § 29.853 for flammability standards of certain materials.
(1) The compartment must be constructed of, or lined with, materials that are at least fire resistant. Accessible and inaccessible compartments must comply.
(2) Inaccessible compartments must be sealed and designed to completely contain a compartment fire or to allow detection as stated in § 29.855(c) and (d).
(3) Inaccessible compartments must have a detector unless the compartment can contain a fire as stated. Accessible compartments must have a detector or be designed to ensure detection by a crewmember while at his station as stated in § 29.855(d). Flight evaluations assure that an inaccessible compartment is sealed and will contain smoke, gases, etc., as stated.
(4) The cabin area may be used for carriage of cargo only as stated in § 29.855(e). Crew emergency exit must be accessible; sources of heat protected, and air flow must be stopped.
(5) Section 29.853 of Amendment 29-17 provides flammability standards for cargo compartment liners, covers, cargo, baggage tiedown equipment, etc., as stated in that section. This section pertains to compartments used by passengers or crew.
Section 29.855(a) requires a fire resistant liner and is the overriding requirement.
b. Procedures. It is intended to provide for adequate protection of the crew and passengers in the event of an in-flight fire. For Category B rotorcraft, one objective as Page D - 115
stated in § 29.861 is that the rotorcraft should be protected for at least 5 minutes (after recognition) in the event of a fire. The correct time interval to consider for Category A or B rotorcraft may be derived from the policy stated in paragraph AC 29.861, § 29.861.
(1) An aluminum inner skin, fire resistant liner, or closure of the compartment, whether the compartment is accessible or inaccessible is required by the rule. In the event of a compartment fire, the inner skin or liner will protect the load-carrying structure from direct flame impingement until the fire is detected and appropriate action is taken.
Flight Standards Service Release No. 453 provides the standards for fire resistant materials.
(2) Inaccessible compartments, in addition to having the inner skin or liner, must be sealed to prevent entry of air and thereby contain a fire in the compartment.
Flight tests are generally necessary to assure the compartment, primarily doors, do not leak in flight. Sensitive pressure measuring equipment (range of 10 inches of H 2O) may be used to prove the compartment is sealed by finding no appreciable change in compartment pressure during ground and flight conditions. The appropriate tests should also be conducted to determine that no accumulation of harmful quantities of smoke, flame , extinguishing agents, or other noxious gases occur in any crew or passenger compartment. For compartments having a volume not in excess of 500 cubic feet, an airflow of not more than 1,500 cubic feet per hour is considered acceptable. For larger compartments lesser airflow may be applicable to assure fires are contained.
(3) Inaccessible compartments may have a detector as prescribed. A smoke detector is preferable in place of a fire detector. The instrument panel will have an illuminated red indicator, such as baggage/cargo, as a warning signal for the flightcrew.
Although no specific standards for the detectors are contained in FAR Part 29, the following standards are recommended. The detection system should be designed to provide a visual indication to the flightcrew within one minute after start of a fire or within 5 minutes after smoke initiation appropriate to the detector used (30 seconds is allowed under TSO C 1b, for smoke detector actuation). There should be a means to allow the crew to check in flight the functioning of each fire or smoke detector circuit. For large compartments, the effectiveness of the detection system should be proven and the detection system should be capable of detecting a fire at a temperature significantly below the temperature at which the structural integrity of the rotorcraft would be substantially decreased.
(4) Accessible compartments must have a detector or detectors unless a crewmember can detect a fire while at his station. Flight evaluations are necessary to assure accessible compartments may be isolated from crew and passenger compartments as stated. The rule envisaged separate compartments for passengers or crew and cargo/baggage.
(5) Insulation blankets, cargo covers, cargo and baggage tie-down equipment, including containers, bins and pallets used in accessible and inaccessible Page D - 116
compartments should meet the flammability standards specified in § 29.853 for the same counterparts noted therein.
AC 29.855A. § 29.855 (Amendment 29-30) CARGO AND BAGGAGE COMPARTMENTS.
a. Explanation. Amendment 29-30 relaxes previous requirements by allowing small, accessible cargo and baggage compartments to be lined with passenger compartment materials rather than fire resistant materials. Materials may meet the § 29.853(a)(1), (a)(2), and (a)(3) requirements for cargo or baggage compartments if:
(1) The presence of a compartment fire would be easily discovered by a crew member while at the crew member’s station.
(2) Each part of the compartment is easily accessible in flight.
(3) The compartment has a volume of 200 cubic feet or less.
b. Procedures. The previous procedures continue to apply to Amendment 29-30 except for allowing the use of passenger compartment materials for accessible compartments.
AC 29.859. § 29.859 (Amendment 29-2) COMBUSTION HEATER FIRE PROTECTION.
a. Explanation. This regulation ens ures that onboard combustion heating systems (of all type designs) are safe during normal and survivable emergency operations. Thus as a minimum, each combustion heater design must meet the requirements of § 29.859.
b. Definitions.
(1) Backfire. An improperly timed det onation (or explosion) of a fuel mixture which results in higher than normal temperatures and pressures.
(2) Reverse flame propagation. An event that occurs when the flame from a controlled combustion process such as a heater, goes in an abnormal path (i.e., either a reverse or different path than the intended path) as a result of a change in internal pressure or internal pressure gradient (e.g., a backfire) from a detonation or a similar event.
(3) Safe distance. A maximum fl ow length dimension determined from the thermodynamics of a worst-case flow reversal (backfire) and the local heater system geometry.
(4) Heater zone (or region). A geom etric zone defined by the heater type, heater size, the location of heater system components, and the maximum safe distance Page D - 117