AC 27-1B, Chg 2 4/25/06
(iii) Flotation time and trim requirements should be evaluated with a simulated, ruptured deflation of the most critical float compartment. Flotation characteristics should be satisfactory in this degraded mode to at least sea state 2 conditions.
(iv) A sea anchor or similar device should not be used when demonstrating compliance with the flotation and trim requirements but may be used to assist in the deployment of liferafts. If the basic flotation system has demonstrated compliance with the minimum flotation and trim requirements, credit for a sea anchor or similar device to achieve stability in more severe water conditions (sea state, etc.) may be allowed if the device can be automatically, remotely, or easily deployed by the minimum flightcrew.
(v) Probable rotorcraft door/window open or closed configurations and probable damage to the airframe/hull (i.e., failure of doors, windows, skin, etc.) should be considered when demonstrating compliance with the flotation and trim requirements.
(4) Float System Reliability. Reliability should be considered in the basic design to ensure approximately equal inflation of the floats to preclude excessive yaw, roll, or pitch in flight or in the water.
(i) Maintenance procedures should not degrade the flotation system
(e.g., introducing contaminants which could affect normal operation, etc.).
(ii) The flotation system design should preclude inadvertent damage due to normal personnel traffic flow and excessive wear and tear. Protection covers should be evaluated for function and reliability.
(iii) Float design should provide a means to minimize the likelihood of damage or tear propagation between compartments. Single compartment float designs should be avoided.
(iv) Where practical, design of the flotation system should consider the likely effects of an uncontrolled water entry and locate system components away from the major effects of structural deformity.
(v) Visual identification of the helicopter following a ditching (and possible capsize) is made easier by the choice of material for the construction of the floats that has high visual conspicuity properties.
(5) Occupant Egress and Survival. The ability of the occupants to deploy liferafts, egress the rotorcraft, and board the liferafts should be evaluated. For configurations which are considered to have critical occupant egress capabilities due to liferaft locations and/or ditching emergency exit locations and floats proximity, an actual demonstration of egress may be required. When a demonstration is required, it may be conducted on a full-scale rotorcraft actually immersed in a calm body of water or using Page D - 88
any other rig/ground test facility shown to be representative. The demonstration should show that floats do not impede a satisfactory evacuation. Service experience has shown that it is possible for occupants to have escaped from the cabin but have not been able to board a liferaft and have had difficulties finding handholds to stay afloat and together. Where practical, handholds or lifelines should be provided. The normal attitude of the rotorcraft and the possibility of a capsize should be considered when locating the handholds or lifelines.
(6) Rotorcraft Flight Manual. The Rotorcraft Fli ght Manual is an important element in the approval cycle of the rotorcraft for ditching. The material related to ditching may be presented in the form of a supplement or a revision to the basic manual. This material should include:
(i) The information pertinent to the limitations applicable to the ditching approval should include the range of sea state conditions that has been demonstrated for water entry and flotation stability. If the ditching approval is obtained in a segmented fashion (i.e., one applicant performing the aircraft equipment installation and operations portion and another designing and substantiating the liferaft/lifevest and ditching safety equipment installations and deployment facilities), the RFM limitations should state “Not Approved for Ditching” until all segments are completed. The requirements for a complete ditching approval not yet completed should be identified in the “Limitations” section.
(ii) Procedures and limitations for flotation device inflation.
(iii) Recommended rotorcraft water entry attitude, speed, and wave position.
(iv) Procedures for use of emergency ditching equipment.
(v) Procedures for ditching egress and raft entry.
(vi) Information stating the flotation system has been certificated for Ditching (as opposed to Emergency Flotation) to facilitate compliance with operational requirements.
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AC 27.801-1
SEA STATE CODE (WORLD METEOROLOGICAL ORGANIZATION) Sea State Significant Wave Height Wind Speed Code Description of Sea Meters Feet Knots 0 Calm (Glassy) 0 0 0-3 1 Calm (Rippled) 0 to 0.1 0 to 1/3 4-6 2 Smooth (Wavelets) 0.1 to 0.5 1/3 to 1 2/3 7-10 3 Slight 0.5 to 1.25 1 2/3 to 4 11-16 4 Moderate 1.25 to 2.5 4 to 8 17-21 5 Rough 2.5 to 4 8 to 13 22-27 6 Very Rough 4 to 6 13 to 20 28-47 7 High 6 to 9 20 to 30 48-55 8 Very High 9 to 14 30 to 45 56-63 9 Phenomenal Over 14 Over 45 64-118 NOTES: (1) The Significant Wave Height is defined as the average value of the height (vertical distance between trough and crest) of the largest one-third of the waves present.
(2) Maximum Wave Height is usually taken to be 1.6 x Significant Wave Height; e.g., Significant Wave Height or 6 meters gives Maximum Wave Height of 9.6 meters.
(3) Winds speeds were obtained from Appendix R of the “American Practical Navigator” by Nathaniel Bowditch, LL.D.; Published by the U.S. Naval Oceanographic Office, 1966.
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AC 27.805 § 27.805 (Amendment 27-37) FLIGHT CREW EMERGENCY EXITS.
a. Explanation.
(1) Amendment 27-37 increases the maximum gross weight of a normal category rotorcraft from 6000 pounds to 7000 pounds and adds a passenger seat limitation of nine. In conjunction with the weight and passenger limitation and to support a potential increase of passengers, § 27.805 was added that required flight crew emergency exits when passenger exits are not convenient. The placement of litters, cargo, or bulkheads may prevent passenger exits from being convenient to the flight crew. Flight crew exits, if required, are to be of sufficient size and located on both sides of the rotorcraft (or one top hatch) to allow “rapid evacuation of the flight crew.” This must be shown by test(s) to demonstrate compliance.
(2) If equipped with emergency flotation devices, the rule requires that the water or flotation devices do not obstruct the flight crew emergency exits after an emergency landing on water. This must be shown by test, demonstration, or analysis.
b. Procedures.
(1) Flight crew emergency exits, if required, may consist of one overhead hatch or two side exits (one on either side). The size is not explicitly defined except that it be “of sufficient size . . . to allow rapid evacuation of the flight crew”. The ability for “rapid evacuation” is to be demonstrated by tests. For side exits located immediately adjacent to the crew seat and exceeding an unobstructed opening that provides a 19- by 26-inch ellipse (§ 27.807) in size, the test demonstration can be accomplished by normal use and evaluation of the exits by the certification authority during Type Inspection Authorization (TIA) testing. For any overhead exit or side of fuselage exits not meeting the 19- by 26-inch ellipse dimensions, a special demonstration test should be accomplished. This demonstration should show that 2.5 percentile to 97.5 percentile men could egress rapidly through the crew exit(s), i.e., men 5 feet 4 inches to 6 feet 5 inches in height and up to 225 pounds in weight, based on the Civil Aeromedical Institute’s (CAMI) 1998 Aeromedical Certification Statistical Handbook. If an overhead hatch type exit is utilized, on conventional rotorcraft designs, hazards associated with the proximity of rotor blades should be considered.
(2) The tests, demonstrations, or analysis required by § 27.805(c) for flight crew exits are analogous to those of § 27.807(a)(3) except the crew exit threshold may be slightly below the water line but should not obstruct use of the exit. Tests in water (tanks or large bodies of water) or demonstrations in the laboratory may be used for compliance if the deflections of flotation devices relative to the exits are accurately or conservatively achieved.
AC 27.807. § 27.807 (Amendment 27-21) EMERGENCY EXITS.
a. Explanation. The specified emergency exits are as follows:
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(1) Quantity, size, and location.
(i) For typical operations.
Passenger Seating Capacity Main Door (MD) Side Side Opposite Main Door 1 through 15 MD (1) 19- by 26-inch ellipse More than 15 MD + additional exit(s)
(1) 19- by 26-inch ellipse + additional exit(s)
(ii) For overwater operations (if ditching certification is requested), one 19- by 26-inch elliptical exit on each side of the fuselage above the waterline.
(iii) Section 27.807(a) was revised by Amendment 27-21 on November 6, 1984, to remove any reference to the seating capacity in excess of 15 seats. For further information, see Amendment 29-21 which, in part, amended § 29.1 on January 31, 1983.
(2) In addition to quantity and size of exits, the rule specifies the following:
(i) The 19- by 26-inch ellipse portion of the exit is to be unobstructed.
(ii) The exits are to be readily accessible.
(iii) The exits must have a simple and obvious method of opening.
(iv) The exits must be readily located and operated in darkness.
(v) The exits must be protected from jamming by fuselage deformation.
b. Procedures.
(1) The quantity and minimum size of exits will be as specified.
(2) Access to the exits will be provided by aisles, break-over seatbacks, or other features as appropriate. If access is questionable, a demonstration shall be conducted to assess the means of access.
(3) The location and operation of the exits should be evaluated in total darkness.
(4) Protection from jamming is normally provided by clearances between the fuselage exit frame and the exit or by exit designs which are basically insensitive to fuselage deformation. NASTRAN or similar analysis methods have been used in the Page D - 92
past to obtain the effects of fuselage deformation on exit clearances during minor crash landings.
AC 27.807A. § 27.807 (Amendment 27-26) EMERGENCY EXITS.
a. Explanation. Amendment 27-26 added § 27.807(d)(3) which requires proof that all rotorcraft ditching configuration exits will also be free of interference from emergency flotation devices, whether stowed or deployed (inflated).
b. Procedures. All of the policy material pertaining to this section remains in effect with the following additions:
(1) Test, demonstration, compliance inspection, or analysis is required to show the “ditching” exits are free from interference from stowed/deployed emergency flotation devices. In the event an analysis is insufficient or a given design is questionable, a demonstrating may be required. The demonstration would consist, as a minimum, of an accurate, full-size replica (or representation) of the rotorcraft and of the flotation devices both before, during, an after their deployment.
(2) The type inspection authorization may be used to perform a detailed compliance evaluation utilizing a full-scale rotorcraft in calm water.
(3) Designs may be accepted “by compliance visual inspection” if location of exit and flotation devices relative to each other ensure that interference is impossible.
In this case, a demonstration is unnecessary.
AC 27.807B § 27.807 (Amendment 27-37) EMERGENCY EXITS.
a. Explanation.
(1) Amendment 27-37 increases the maximum gross weight of a normal category rotorcraft from 6000 pounds to 7000 pounds and adds a passenger seat limitation of nine. In conjunction with the weight and passenger limitation and to support a potential increase of passengers, § 27.807 was completely rewritten to include the previous requirements but was revised to require at least one emergency exit on each side of the cabin readily accessible for each passenger. This is required regardless of whether the rotorcraft has a closed cabin or is ditching certified. In addition, at least one of the required exits must be usable in any probable attitude that may result from a crash. Doors intended for use during normal operations may also serve as emergency exits provided these doors comply with requirements specified for emergency exits..
(2) Each emergency exit must provide an unobstructed minimum opening equivalent to a 19-inch x 26-inch ellipse. The methods of opening or operating the emergency exit must be simple and obvious from both inside and outside the rotorcraft.
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AC 27-1B, Chg 1 2/12/03
(3) If equipped with emergency flotation devices, the revised rule still requires that the water or flotation devices do not obstruct the emergency exits whether stowed or deployed and the emergency exits must be above the water line. This must be shown by test, demonstration, or analysis. In addition, if certification with ditching provisions is requested, § 27.807(d) requires the emergency exit markings must remain visible if the rotorcraft is capsized and the cabin is submerged.
b. Procedures. The advisory material pertaining to this section is still in effect wi th the following additions.
(1) There must be at least one emergency exit on each side of the rotorcraft.
As a minimum, one of these exits must be usable in any probable attitude that may result from a crash.
(2) Each emergency exit must provide an unobstructed opening that is equivalent to a 19-inch x 26- inch ellipse. Each emergency exit must have simple and obvious methods of opening from the inside and the outside of the rotorcraft.
(3) Emergency exits are arranged and marked so that they are readily located and opened, even in darkness, and that they are reasonably protected from jamming by fuselage deformation.
(4) Functional tests of each emergency exit must be performed.
(5) If emergency flotation devices are installed, then tests, demonstration, or analysis are required to show that each emergency exit used for a ditching exit is above the water line and will open without interference from flotation devices, whether stowed or deployed. In addition, the required emergency exit markings must remain visible if the rotorcraft is capsized and the cabin is submerged.
AC 27.831. § 27.831 VENTILATION.
a. Explanation.
(1) This rule specifies minimum ventilation requirements for each passenger and crew compartment. The passenger and crew compartments are required to be free from harmful or hazardous concentration of gases or vapors, and specifically for carbon monoxide, its concentration may not exceed 1 part in 20,000 parts of air during forward flight or hovering in still air.
(2) Failure conditions must also be considered when evaluating the ventilation system, and § 27.1309 is used to cover these aspects. Malfunctions concerning the ventilation system are covered here to make the discussion complete in one paragraph.
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(3) This system becomes more significant when engine bleed air is used for conditioning of the passenger and crew compartment’s air. Certain data are necessary in order to analyze properly 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 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 crew stations, and outlets and different combinations of windows closed/open, heat off/on, air-conditioner off/on, etc., are checked to ensure all conditions are evaluated.
(2) When engine bleed air is used to condition the passenger and crew compartment’s 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.
(3) 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.
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AC 27.833. § 27.833 (Amendment 27-23) HEATERS.
a. Explanation.
(1) Amendment 27-23 added § 27.833 for combustion heaters which is derived from the lead-in paragraph of § 27.859(c) which relates to the fire protection requirements for fuel heaters. Section 27.833 was needed to facilitate the extensive changes made to § 27.859 and to achieve parallel rule construction with Part 29. This will ensure that all combustion heaters will be approved whether as a part of the type design or as a TSO approved combustion heater.
(2) Section 27.833 requires that each combustion heater be approved. The standard contains no provisions regarding functioning of the system, environmental considerations, or malfunctions; therefore, the provisions of §§ 27.1301 and 27.1309 should be used to evaluate those aspects of an installation. The ventilation provisions of § 27.831 should be considered as well as the fire protection and installation provisions of § 27.859.
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 is qualified to the provisions of TSO-C20, it may be approved. If a unit is not TSO qualified, a qualification program for the heater itself in conjunction with the installation should be established. This program under the type design change procedures should be equal or equivalent to provisions of the TSO-C20.
(2) The TSO refers to the SAE Aeronautical Standard, AS 143B, which specifies the use of certain additional devices, design features, air supply considerations, performance tests, safety controls, environmental considerations, and so forth. Compliance with 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, an environmental spectrum more suitable to rotorcraft may be used by referring to the latest version of Document No. RTCA/DO-160, Environmental Conditions and Test Procedures for Airborne Equipment, rather than the older AS 143B. Similarly, other specifications may also be satisfactory for compliance with the standard.
(3) The heater system installation evaluation should also consider functioning of the system based upon the provisions of § 27.1301 (see paragraph AC 27.1301).
Section 27.1309(a) is the regulatory basis for also considering environmental conditions (see paragraph AC 27.1309). The expected environmental conditions resulting from the particular rotorcraft installation should be compared to those specified in the TSO. If the conditions derived for § 27.1309 are not met, additional environmental considerations are appropriate. The provisions of § 27.1309(b) should be used to evaluate the possible malfunctions of the installed system. Such an evaluation should be Page D - 96
documented in a fault analysis. The air quality provisions of § 27.831 apply since certain standards of “ventilation air quality,” under normal and malfunction conditions, should comply (see paragraph AC 27.831). The provisions of § 27.859 apply. See paragraph AC 27.859 for information.
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SUBPART D - DESIGN AND CONSTRUCTION
FIRE PROTECTION AC 27.853 § 27.853 (Amendment 27-17) COMPARTMENT INTERIORS.
a. Explanation.
(1) Crew and passenger compartments must have materials that are at least flash resistant or flame resistant as prescribed for the application cited in the standard.
(2) Whenever smoking is allowed, self-contained, removable ashtrays must be provided as stated. A placard or placards, if needed, may be used to prohibit smoking at all times in the crew and passenger compartment. If smoking is allowed, illuminated “no smoking” signs are required. The signs shall meet prescribed standards for passenger compartments that are separate from the flightcrew. Integral crew and passenger compartments (of smaller rotorcraft) do not require illuminated signs since oral commands or instructions from the flightcrew are sufficient.
(3) Amendment 27-17 revised paragraph (c) of § 27.853 by adding the standards for the “no smoking” illuminated signs that must be controllable by the flightcrew. Amendment 29-18 added the same standards for FAR Part 29 transport rotorcraft. The standard requires at least one illuminated sign for use in daylight as well as night in passenger compartments that are separate from the crew compartment. The sign shall be legible to each seated passenger. If forward and aft facing seats are installed, signs for each seat orientation may be needed as prescribed.
Section 29.853(c) of Amendment 29-18 is the same standard as § 27.853(c) of Amendment 27-17.
(4) Advisory Circular 23-2, Flammability Tests, August 20, 1984, provides historical background of the regulatory standards for flash resistant, flame resistant, fire resistant, and fireproof materials. The procedures in AC 23-2 may be used for FAR Part 27 standards. Section 27.853 does not impose standards for mandatory use of self-extinguishing materials. Nevertheless, the FAA/AUTHORITY encourages and recommends use of self-extinguishing interior materials that comply with § 29.853 of Amendment 29-17.
(5) Flammability standards for certain electrical wires or cables are specified in § 27.1365. See paragraph AC 27.1365 for information about electrical wires.
b. Procedures.
(1) Aircraft interior materials including consoles, cabinets, etc., are subject to the standards.
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(2) Advisory Circular 23-2 may be referred to in preparation of test proposals for flammability tests of interior materials.
(3) A placard prohibiting smoking may be used if ashtrays are not provided. If ashtrays are provided, an adequate number shall be provided, and the installation must have an inner fire resistant liner to close off the ashtray cavity or receptacle when the ashtray is removed.
(4) All illuminated “no smoking” sign or signs must be used when prescribed.
Flightcrew must be able to control illumination of the signs.
(5) If a hand-held fire extinguisher is installed to comply with an operating rule, Advisory Circular 20-42C, Hand Fire Extinguishers for Use in Aircraft, contains acceptable information about hand-held fire extinguishers.
AC 27.853A § 27.853 (Amendment 27-37) COMPARTMENT INTERIORS.
a. Explanation. Amendment 27-37 requires all materials in the cabin area to be flame resistant. Section 27.853(b) is now reserved, as the flammability requirements are not dependent on interior material location or function.
b. Procedures. The procedures of paragraph AC 27.853 still apply to the flammability requirements of interior materials except all interior materials must be flame resistant.
AC 27.855 § 27.855 CARGO AND BAGGAGE COMPARTMENTS.
a. Explanation.
(1) Cargo and baggage compartments must be constructed of or lined with--
(i) Fire resistant material; or
(ii) Flame resistant material for compartments readily accessible to the crew while in flight.
(2) A liner or a separately constructed compartment shall protect the aircraft structure from significant loss of strength in the event of a compartment fire.
(3) Whenever essential or critical controls, wiring, lines, etc., are located in a compartment, they must be protected as prescribed.
(4) For historical reference, this design standard was adopted in 1953 by Amendment 6-4 to CAR Part 6 for normal category rotorcraft and adopted into FAR Part 27. The expressed interest, paraphrased from the preamble for the Page D - 99