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a fire hazard in the compartment. Provision shall be made to prevent cargo or baggage from interfering with the functioning of the fire-protective features of the compartment. All materials used in the construction of cargo or baggage compartments, including tie-down equipment, shall be flame-resistant or better. In addition, all cargo and baggage compartments shall include provisions for safeguarding against fires according to the following classifications:
(a) Cargo and baggage compartments shall be classified in the "A" category. if presence of a possible fire therein can be readily discernible to a member of the crew while at his station. and if all parts of the compartment are easily accessible in flight. A hand fire extinguisher shall be available for such compartment.
(b) Cargo and baggage compartments shall be classified in the "B" category. if sufficient access is provided while in flight to enable a member of the crew to more by hand all contents and to reach effectively all parts of the compartment with a hand fire extinguisher. Furthermore, the design of the compartment shall be such that, when the access provisions are being used, no hazardous quantity of smoke, flames, or extinguishing agent will enter any compartment occupied by the crew or passengers. Each compartment in this category shall be equipped with a separate system of an approved type smoke detector or fire detector other than heat detector to give warning at the pilot or flight engineer station. Hand fire extinguishers shall be readily available for use in all compartments of this category. Compartments in this category shall be completely lined with fire-resistant material, except that additional service lining of flame-resistant material may be employed.
(c) Cargo and baggage compartments shall be classified in the "C" category, if they do not conform with the requirements for the "A" or "B" categories. Each compartment of the "C" category shall be equipped with: (1) A separate system of an approved type smoke detector or fire detector other than heat detector to give warning at the pilot or flight engineer station. and (2) an approved built-in ire-extinguishing system controlled from the pilot or flight engineer station. Means shall be provided to exclude hazardous quantities of smoke, flames, or extinguishing agent from entering into any compartment occupied by the crew or passengers. Ventlation and drafts shall be further controlled within each such cargo or baggage compartment to the extent that the extinguishing agent provided can control any fire which may start within the compartment. All cargo and baggage compartments of this category shall be completely lined with fire-resistant material, except that additional service lining of flame-resistant, material may be employed.
§ 40.116 Proof of compliance. Compliance with those provisions of § 40.115 which refer to compartment accessibility, the entry of hazardous quantities of smoke or extinguishing agent into compartments occupied by the crew or passengers, and the dissipation of the extinguishing agent in category "C" compartments shall be demonstrated by tests in flight. It shall also be demonstrated during these tests that no inadvertent operation of smoke or fire detectors in adjacent or other compartments within the airplane would occur as a result of fire contained in any one compartment. either during or after extinguishment, unless the extinguishing system floods such compartments simultaneously.
§ 40.117 Propeller de-icing fluid. If combustible fluid is used for propeller de-icing, the provisions of §§ 40.131 through so 135 shall be complied with.
§ 40.118 Pressure cross-feed, arrangements. Pressure cross-feed lines shall not pass through portions of the airplane devoted to carrying personnel or cargo unless means are provided to permit the flight personnel to shut off the supply of fuel to these lines, or unless the lines are enclosed in a fuel and fume-proof enclosure that is ventilated and drained to the exterior of the airplane. Such enclosures need not be used if these lines incorporate no fillings on or within the personnel or cargo areas and are suitably routed or protected to safe-guard against accidental damage. Lines which can be isolated from the remainder of the fuel system by means of valves at each end shall incorporate provisions for the relief of excessive pressures that may result from exposure of the isolated line to high ambient temperatures.
§ 40.119 Location of fuel tanks. Location of fuel tanks shall comply with the provisions of §40.132. In addition, no portion of engine nacelle skin which lies immediately behind a major air egress opening from the engine compartment shall act as the wall of an integral tank. Fuel tanks shall be isolated from personnel compartments by means of fume and fuel-proof enclosures.
§ 40.120 Fuel system lines and fittings. Fuel lines shall be installed and supported in a manner that will prevent excessive vibration and will be adequate to withstand loads due to fuel pressure and accelerated flight conditions. Lines which are connected to components of the airplane between which relative motion may exist shall incorporate provisions for flexibility. Flexible connections in lines which may be under pressure and subjected to axial loading shall employ flexible hose assemblies rather than hose clamp connections. Flexible hose shall be of an acceptable type or proven suitable for the particular application.
§ 40.121 Fuel lines and fittings in designated fire zones. Fuel lines and fittings in all designated fire zones (see § 40.131) shall comply with the provisions of § 40.134.
§ 40.122 Fuel values. In addition to the requirements contained in §40.133 for shutoff means. all fuel valves shall be provided with positive stops or suitable index provisions in the "on" and "on" positions and shall be supported in such a manner that, loads resulting from their operation or from accelerated flight conditions are not transmitted to the lines connected to the valve.
§ 40.123 Oil lines and fittings in designated fire zones. Oil lines and fittings in all designated fire zones (see §40.131) shall comply with the provisions of § 40.134.
§ 40.124 Oil values. Requirements of § 40.133 for shutoff means shall be complied with. Closing of oil shutoff means shall not prevent feathering the propeller, unless equivalent safety provisions are incorporated. All oil valves shall be provided with positive stops or suitable index provisions in the "on" and "off" positions, and shall be supported in such a manner that loads resulting from their operation or from accelerated flight conditions are not transmitted to the lines attached to the valve.
§ 40.125 Oil system drains. Accessible drains shall be provided to permit safe drainage of the entire all system and shall incorporate means for positive or automatic locking in the closed position. (See also §40.135).
§ 40.126 Engine breather line. Engine breather lines shall be so arranged that condensed water vapor which may freeze and obstruct the line cannot accumulate at any point. Breathers shall discharge in a location which will not constitute a fire hazard in case foaming occurs and so that oil emitted from the line will not impinge upon the pilots windshield. The breather shall not discharge into the engine air induction system. (See also § 40.135).
§ 40.127 Fire walls. All engines, auxiliary power units, fuel-burning heaters, and other combustion equipment which are intended for operation in flight shall be isolated from the remainder of the airplane by means of fire walls or shrouds, or other equivalent means.
§ 40.128 Fire-wall construction. Fire walls and shrouds shall be constructed in such a manner that no hazardous quantity of air, fluids, or flame can pass from the engine compartment to other portions of the airplane. All openings in the fire wall or shroud shall be sealed with close-fitting fireproof grommets, bushings, or fire—wall fittings. Fire walls and shrouds shall be constructed of fireproof material and shall be protected against corrosion. The following materials have been found to comply with this requirement:
(a) Heat and corrosion resistant steel 0.015 inch thick:
(b) Low carbon steel, suitably protected against corrosion. 0.018 inch thick.
§ 40.129 Cowling. Cowling shall be constructed and supported in such a manner as to be capable of resisting all vibration, inertia, and air loads to which it may normally be subjected. Provision shall be made to permit rapid and complete drainage of all portions of the cowling in all normal ground and flight attitudes. Drains shall not discharge in
