(4) During the test, the tank assembly shall be rocked at the rate of 16 to 20 complete cycles per minute through an angle of 15° on either side of the horizontal (30° total) about the most critical axis for 25 hours. If motion about more than one axis is likely to be critical, the tank shall be rocked about each axis for 121⁄2 hours.

§ 7.422 Fuel tank installation.

(a) The method of support for fuel tanks shall not permit harmful concentrations of loads, resulting from the weight of the fuel in the tank, on unsupported tank surfaces. The following shall be applicable:

(1) Pads shall be provided, if necessary, to prevent chafing between the tank and its supports.

(2) Materials employed for padding shall be nonabsorbent or shall be treated to prevent the absorption of fluids.

(3) If flexible tank liners are employed they shall be so supported that the liner is not required to withstand fluid loads.

(4) Interior surfaces of tank compartments shall be smooth and free of projections which could cause wear of the liner, unless provisions are made for protection of the liner at such points or unless the construction of the liner itself provides such protection.

(b) Spaces adjacent to the surfaces of the tank shall be ventilated consistent with the size of the compartment to avoid accumulation of fuel or fumes in these spaces due to minor leakage. If the tank is in a sealed compartment, it shall be acceptable to limit the ventilation to that provided by drain holes of sufficient size and disposition to prevent clogging and to prevent excessive pressure resulting from altitude changes. If flexible tank liners are installed, the design of the venting arrangement for the spaces between the liner and its container shall take into consideration the need for maintaining proper relationship to tank vent pressures for all expected flight conditions.

(c) Location of fuel tanks shall comply with the provisions of § 7.481 (b).

(d) No portion of rotorcraft skin which lies immediately adjacent to a major air egress opening from the engine compartment shall act as the wall of an integral tank.

(e) Fuel tanks shall be isolated from personnel compartments by means of fumeproof and fuelproof enclosures.

(f) Fuel tanks located in close proximity to personnel compartments, engines, or combustion heaters shall be so designed or protected and installed as to assure that they will retain their contents in accidents of a severity which will produce the decelerations specified in § 7.260.

§ 7.423 Fuel tank expansion space.

Fuel tanks shall be provided with an expansion space of not less than 2 percent of the tank capacity. It shall not be possible to fill the fuel tank expansion space inadvertently when the rotorcraft is in the normal ground attitude. § 7.424 Fuel tank sump.

(a) Each fuel tank shall be provided with a sump having a capacity of not less than either 0.10 percent of the tank capacity or one-sixteenth of a gallon, whichever is greater.

(b) The fuel tank sump capacity specified in paragraph (a) of this section shall be effective with the rotorcraft in all normal flight and ground attitudes, and shall be located so that the sump contents cannot be drawn out through the tank outlet opening. The fuel tank shall be constructed to permit drainage of any hazardous quantity of water from all portions of the tank to the sump when the rotorcraft is in the ground attitude.

(c) Fuel tank sumps shall be provided with an accessible and easily operable drain to permit complete drainage of the sump on the ground. The drain shall discharge clear of all portions of the rotorcraft and shall be provided with means for positive locking of the drain in the closed position, either manually or automatically.

§ 7.425 Fuel tank filler connection.

(a) The design of fuel tank filler connections shall be such as to prevent the entrance of fuel into the fuel tank compartment or to any other portion of the rotorcraft other than the tank itself. The fuel tank filler shall be marked as prescribed in § 7.738 (b) (1).

(b) Recessed fuel tank filler connections which can retain any appreciable quantity of fuel shall incorporate a drain, and the drain shall discharge clear of all portions of the rotorcraft.

(c) The fuel tank filler cap shall provide a fuel-tight seal under the pressure expected to be encountered in normal operation.

(d) Category A: Fuel tank filler caps or filler cap covers shall incorporate features which provide a warning indication when caps are not fully locked or seated on the filler connection.

§ 7.426

Fuel tank vents and carburetor vapor vents.

(a) Fuel tanks shall be vented from the top portion of the expansion space in such a manner that venting of the tank is effective under all normal flight conditions. The following shall be applicable:

(1) The vents shall be arranged to avoid stoppage by dirt or ice formation.

(2) The vent arrangement shall be constructed to preclude the possibility of siphoning fuel during normal operation.

(3) The venting capacity and vent pressure levels shall be appropriate for the tank installation so as to maintain acceptable differences of pressure between the interior and exterior of the tank during normal flight operation, during maximum rate of ascent and descent, and, if applicable, during refueling and defueling.

(4) Air spaces of tanks with interconnected outlets shall also be interconnected.

(5) There shall be no points in the vent line where moisture could accumulate with the rotorcraft in either the ground or the level flight attitude unless drainage is provided.

(6) Vents and drainage shall not terminate at points where the discharge of fuel from the vent outlet would constitute a fire hazard or from which fumes could enter personnel compartments.

(b) Carburetors which are provided with vapor elimination connections shall be provided with a vent line to lead vapors back to one of the fuel tanks. The vents shall comply with the following:

(1) Provisions shall be incorporated in the vent system to avoid stoppage by ice. (2) If more than one fuel tank is provided and it is necessary to use the tanks in a definite sequence, the vapor vent return line shall lead back to the fuel tank used for take-off and landing.

§ 7.427 Fuel tank outlet.

A fuel strainer of 8 to 16 meshes per inch shall be provided either for the fuel tank outlet or for the booster pump. Strainers shall comply with the following:

(a) The clear area of the fuel tank outlet strainer shall not be less than 5 times the area of the fuel tank outlet line.

(b) The diameter of the strainer shall not be less than the diameter of the fuel tank outlet.

(c) Finger strainers shall be accessible for inspection and cleaning.

§ 7.428 Pressure refueling and fueling provisions below fuel level in the tank.

Fueling connections located below the fuel level in a tank shall be provided with means to prevent the escape of hazardous quantities of fuel from the tank in the event of malfunctioning of the fuel entry valve. For systems intended for pressure refueling, in addition to the normal means provided in the rotorcraft for limiting the tank content, a means shall be installed to prevent damage to the tank in case of failure of the normal means. FUEL SYSTEM COMPONENTS Fuel pumps.

§ 7.430

(a) Main pumps. (1) If the engine fuel supply is maintained by means of pumps which are not an integral part of the fuel control system certificated as part of the engine, at least one fuel pump for each engine shall be enginedriven.

(2) All positive displacement fuel pumps shall incorporate an integral bypass unless provision is made for a continuous supply of fuel to all engines in case of failure of any one pump. Engine fuel injection pumps which are approved as an integral part of the engine need not incorporate a by-pass.

(b) Emergency pumps. Emergency fuel pumps shall be available for immediate use in case of failure of any other fuel pump. No manipulation of fuel valves shall be necessary on the part of the crew to make an emergency fuel pump available to the engine which it is normally intended to serve when the fuel system is being operated in the configuration complying with the provisions of § 7.411.

§ 7.431

Fuel pump installation.

(a) Provision shall be made to maintain the fuel pressure at the inlet to the carburetor within the range of limits established for proper engine operation.

(b) When necessary for the maintenance of the proper fuel delivery pressure, a connection shall be provided to transmit the carburetor air intake static pressure to the proper fuel pump relief valve connection. In such cases, to avoid erroneous fuel pressure readings, the gauge balance lines shall be independently connected to the carburetor inlet pressure.

(c) The installation of fuel pumps having seals or diaphragms which may be susceptible to leakage shall incorporate provisions for draining away leaking fuel. Drain lines shall terminate at points where discharge of fuel will not create a fire hazard.

§ 7.432 Fuel system lines and fittings. (a) Fuel lines shall be installed and supported to prevent excessive vibration and to withstand loads due to fuel pressure, valve actuation, and accelerated flight conditions.

(b) Fuel lines which are connected to components of the rotorcraft between which relative motion could exist shall incorporate provisions for flexibility.

(c) Flexible connections in fuel lines which may be under pressure or subjected to axial loading shall employ flexible hose assemblies rather than hose clamp connections.

(d) Flexible hose shall be of an approved type suitable for the application.

(e) Flexible hoses which might be adversely affected by exposure to high temperatures shall not be employed in locations where excessive temperatures will exist during operation or after engine shutdown.

§ 7.433 Fuel lines and fittings in designated fire zones.

Fuel lines and fittings in all designated fire zones (see § 7.480) shall comply with the provisions of § 7.483.

operation or from accelerated flight conditions are not transmitted to the lines attached to the valve.

§ 7.435 Fuel strainer.

(a) A strainer incorporating a sediment trap and drain shall be provided in the fuel system between the fuel tanks and the engine and shall be installed in an accessible location.

(b) The strainer shall provide the necessary degree of protection for the fuel pumps, fuel controls, and the engine against dirt, sediment, and other foreign matter which might be present in the fuel. The screen or straining element shall be able to be easily cleaned.

(c) The strainer shall be mounted in a manner not to cause its weight to be supported by the connecting lines or by the inlet or outlet connections of the strainer itself.

§ 7.436 Fuel system drains.

Complete drainage of the system shall be accomplished by fuel strainer drains and other drains as provided in § 7.424 with the rotorcraft in its normal ground attitude. The following shall apply:

(a) Drains shall discharge clear of all portions of the rotorcraft and shall incorporate means for positive locking of the drain in the closed position, either manually or automatically.

(b) All fuel system drains shall be accessible.

(c) If drainage of the fuel strainer permits compliance with paragraphs (a) and (b) of this section, no additional drains need be provided unless it is possible for a hazardous quantity of water or sediment to be trapped therein. also § 7.483 (c).)

§ 7.437 Fuel quantity indicator.

(See

The fuel quantity indicators (see §§ 7.604 (e) and 7.613(b)) shall be installed to clearly indicate to the flight crew the quantity of fuel in each tank in flight. When two or more tanks are closely interconnected by a gravity feed system and vented, and it is impossible to feed from each tank separately, only one fuel quantity indicator need be installed.

§ 7.438 Low fuel warning device.

On rotorcraft with more than one fuel tank there shall be installed in addition to the fuel quantity indicators (see

§ 7.604), warning devices to indicate when the fuel in any tank becomes low.

NOTE: The fuel in any tank is considered to be low when there remains approximately a five-minute usable fuel supply with the rotorcraft in the most critical sustained flight attitude.

OIL SYSTEM

§ 7.440 General.

(a) Each engine shall be provided with an independent oil system capable of supplying the engine with an appropriate quantity of oil at a temperature not exceeding the maximum which has been established as safe for continuous operation. The oil system for components of the rotor drive system which require continuous lubrication shall be independent of the lubrication systems of the engines to whatever extent is necessary to assure the ability to operate with any engine inoperative and to assure the ability to autorotate safely. (For oil system instruments see §§ 7.604 and 7.735.)

(b) The usable oil capacity shall not be less than the product of the endurance of the rotorcraft under critical operating conditions and the maximum permissible oil consumption of the engine under the same conditions to which product a suitable margin shall be added to assure adequate circulation and cooling of the oil system. In lieu of a rational analysis of rotorcraft endurance and oil consumption, the total usable oil capacity of 1 gallon for each 40 gallons of usable fuel capacity, by volume, shall be considered acceptable for reciprocating engine installations.

(c) Oil-fuel ratios lower than those prescribed in paragraph (b) of this section shall be acceptable if substantiated by data on the actual oil consumption of the engine.

(d) The ability of the engine and rotor drive system oil cooling provisions to maintain the oil temperature at or below the maximum established value shall be demonstrated in accordance with pertinent provisions of §§ 7.450 through 7.455.

tank capacity or 0.5 gallon, whichever is greater.

(2) Reserve oil tanks which have no direct connection to any engine shall have an expansion space which is not less than 2 percent of the tank capacity.

(3) It shall not be possible to fill the oil tank expansion space inadvertently when the rotorcraft is in the normal ground attitude.

(b) Oil tank filler connection. (1) Recessed oil tank filler connections which can retain any appreciable quantity of oil shall incorporate a drain, and the drain shall discharge clear of all portions of the rotorcraft.

(2) The oil tank filler cap shall provide an oil-tight seal under the pressure expected to be encountered in operation.

(3) Category A: Oil tank filler caps or filler cap covers shall incorporate features which provide a warning indication when caps are not fully locked or seated on the filler connection.

(4) The oil filler shall be marked as prescribed in § 7.738 (b) (2).

(c) Oil tank vent. (1) Oil tanks shall be vented from the top portion of the expansion space in such a manner that venting of the tank is effective under all normal flight conditions.

(2) Oil tank vents shall be arranged so that condensation of water vapor which might freeze and obstruct the line cannot accumulate at any point. (See also § 7.483 (c).)

(d) Oil tank outlet. Provision shall be made either to prevent entrance into the tank itself or into the tank outlet of any foreign object which might obstruct the flow of oil through the system. The oil tank outlet shall not be enclosed by any screen or guard which would reduce the flow of oil below a safe value at any operating temperature condition.

(e) Flexible oil tank liners. Flexible oil tank liners shall be of an approved type or shall be shown to be suitable for the particular application.

§ 7.442 Oil tank tests.

(a) Oil tanks shall be capable of withstanding without failure all vibration, inertia, and fluid loads to which they would be subjected in operation.

(b) The provisions of § 7.421 shall be applicable to oil tanks, except that the test pressure specified in § 7.421 (a) shall be 5 psi.

(a) General. The provisions of § 7.432 shall be applicable to oil lines.

(b) Lines and fittings in designated fire zones. Oil lines and fittings in all designated fire zones (see § 7.480) shall comply with the provisions of § 7.483.

(c) Breather lines. (1) Breather lines shall be arranged so that condensation of water vapor which might freeze and obstruct the line cannot accumulate at any point.

(2) Breathers shall discharge in a location which will not constitute a fire hazard in case foaming occurs and in a manner so that the emitted oil will not impinge upon the pilots' windshield.

(3) The breather shall not discharge into the engine air induction system. (See also § 7.483 (c).)

The powerplant cooling provisions shall be capable of maintaining the temperatures of all powerplant components, engine fluids, and the carburetor intake air within safe values under all conditions of ground and flight operation. Cooling provisions shall also be provided to maintain the fluids in any power transmission within safe values under conditions of ground and flight operations. (For cooling system instruments see §§ 7.604 and 7.734.) § 7.451 Cooling tests.

(a) General. Compliance with the provisions of § 7.450 shall be demonstrated by flight tests in which the temperatures of selected powerplant components, engine (s), and transmission fluids are obtained under critical ground, water, and flight operating conditions. If the tests are conducted under conditions which deviate from the maximum anticipated air temperature (see paragraph (b) of this section), the recorded powerplant temperatures shall be corrected in accordance with the provisions of paragraphs (c) and (d) of this section. The corrected temperatures determined in this manner shall not exceed the maximum established safe values. The fuel used during the cooling tests shall be of the minimum octane number approved for the engine(s) involved, and the mixture settings shall be those ! used in normal operation. The test procedures shall be as outlined in §§ 7.452 through 7.455.

(b) Maximum anticipated air temperature. The maximum anticipated air temperature (hot-day condition) shall be 100° F. at sea level, decreasing from