Compliance with the provisions of § 6.450 shall be demonstrated in flight tests in which engine temperature measurements are obtained under critical flight conditions. Such tests shall be conducted in air at temperatures corresponding with the maximum anticipated air temperatures as specified in paragraph (a) of this section. If the tests are conducted under conditions which deviate from the maximum anticipated air temperature, the recorded powerplant temperatures shall be corrected in accordance with the provisions of paragraphs (b) and (c) 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 engines involved, and the mixture settings shall be those used in normal operation.

(a) Maximum anticipated air temperature. The maximum anticipated air temperature (hot day condition) shall be 100° F. at sea level, decreasing from this value at the rate of 3.6° F. per thousand feet of altitude above sea level until a temperature of -67° F. is reached above which altitude the temperature shall be constant at -67° F.

(b) Correction factor for cylinder head and oil inlet temperatures. The cylinder head and oil inlet temperatures

shall be corrected by adding the difference between the maximum anticipated air temperature and the temperature of the ambient air at the time of the first occurrence of maximum cylinder head or oil inlet temperature recorded during the cooling test, unless a more rational correction is shown to be applicable.

(c) Correction factor for cylinder barrel temperatures. Cylinder barrel temperatures shall be corrected by adding 0.7 of the difference between the maximum anticipated air temperature and the temperature of the ambient air at the time of the first occurrence of the maximum cylinder barrel temperature recorded during the cooling test, unless a more rational correction is shown to be applicable.

INDUCTION AND EXHAUST SYSTEMS

(a) The engine air induction system shall be designed to supply the proper quantity of air to the engine under all conditions of operation.

(b) Cold air intakes shall open completely outside the cowling unless the emergence of backfire flames is positively prevented.

(c) Carburetor air intakes shall be provided with drains. The drains shall not discharge fuel in the possible path of exhaust flames.

§ 6.461-1 Induction system air filters (FAA policies which apply to § 6.641).

When air filters or equivalent fine mesh screens are provided in both the cold and warm air inlets a suitable bypass arrangement should be incorporated to assure continued engine operation in the event both filters become clogged with dirt, ice, or other foreign matter. The bypass may be operated either automatically or manually1 or both.

(a) The bypass should comply with the deicing and anti-icing provision of § 6.462.

1 For manual operation, the normal means for detecting engine power or r. p. m. losses due to restriction in carburetor airflow may be considered adequate warning for the crew to operate the bypass.

(b) A bypass need not be provided for an induction system which employs an air filter or screen when:

(1) The induction system is provided with sufficient preheat' to assure deicing of the filter or screen, and

(2) The filter or screen is the selfcleaning type and so located that it can be deiced by the application of the heated air.

[Supp. 12, 22 F. R. 4877, July 11, 1957]

§ 6.462 Induction system de-icing and anti-icing provisions.

(a) The engine air induction system shall incorporate means for the prevention and elimination of ice accumulations. Unless it is demonstrated that this can be accomplished by other means, compliance with the following heat rise provisions shall be demonstrated in air free of visible moisture at a temperature of 30° F. when the engine is operating at 75 percent of its maximum continuous power.

(b) Rotorcraft equipped with sea level engines employing conventional venturi carburetors shall have a preheater capable of providing a heat rise of 90° F.

(c) Rotorcraft equipped with sea level engines employing carburetors which embody features tending to reduce the possibility of ice formation shall be provided with a sheltered alternate source of air. The preheat supplied to this alternate air intake shall be not less than that provided by the engine cooling air downstream of the cylinders.

(d) Rotorcraft equipped with altitude engines employing conventional venturi carburetors shall have a preheater capable of providing a heat rise of 120° F.

(e) Rotorcraft equipped with altitude engines employing carburetors which embody features tending to reduce the possibility of ice formation shall have a preheater capable of providing a heat rise of 100° F., except that if a fluid deicing system is used the heat rise need not be greater than 40° F.

§ 6.463 Exhaust manifolds.

(See also § 6.383.) (a) Exhaust manifolds shall be designed to provide for expansion, and shall be arranged and cooled so that local hot points cannot form.

'Recommended preheat is 100° F.

(b) Exhaust manifolds shall be installed in accordance with the provisions of subparagraphs (1) through (3) of this paragraph:

(1) Exhaust manifolding shall be such that exhaust gases are discharged clear of cowling, rotorcraft structure, carburetor air intake, and fuel system parts or drains.

(2) Exhaust manifolding shall not be located immediately adjacent to or under the carburetor or fuel system parts unless such parts are protected against leakage.

(3) Exhaust manifolding shall be such that exhaust gases do not discharge in a manner which would impair pilot vision at night due to glare.

POWERPLANT CONTROLS AND ACCESSORIES Powerplant controls; general.

§ 6.470

(a) A separate throttle control shall be provided for each engine. Throttle controls shall be grouped and arranged to permit separate control of each engine and also simultaneous control of all engines.

(b) Throttle controls shall afford a positive and immediately responsive means of controlling the engines.

§ 6.472 Ignition switches.

(a) Means shall be provided for quickly shutting off all ignition by the grouping of switches or by providing a master ignition control.

(b) If a master ignition control is provided, a guard shall be incorporated to prevent inadvertent operation of the control.

The powerplant installation shall be protected against fire in accordance with §§ 6.481 through 6.486. Additional fire prevention requirements are prescribed in Subpart D, Design and Construction, and Subpart F Equipment.

NOTE: The powerplant fire protection provisions are intended to insure that the main and auxiliary rotors and controls remain operable, the essential rotorcraft structure remains intact, and that the passengers and crew are otherwise protected for a period of at least 5 minutes after the start of an engine fire to permit a controlled autorotational landing.

[21 F.R. 10291, Dec. 22, 1956, as amended by Amdt. 604, 24 F.R. 7074, Sept. 1, 1959]

Compartments which include powerplant installation shall have provision for ventilation.

§ 6.482 Shutoff means.

Means shall be provided to shut off the flow in all lines carrying flammable fluids into the engine compartment, except that a shutoff means need not be provided in lines forming an integral part of an engine. Provision shall be made to guard against inadvertent operation of the shutoff means, and to make it possible for the crew to reopen the shutoff means in flight after it has once been closed. Shutoff valves and their controls shall be located on the remote side of the fire wall from the engine, unless it is shown that the valve will perform its intended functions under all fire conditions likely to result from an engine fire. In installations using engines of less than 500 cu. in. displacement, shutoff means need not be provided for engine oil systems. § 6.483 Fire wall.

(a) Engines shall be isolated from personnel compartments by means of fire walls, shrouds, or other equivalent means. They shall be similarly isolated from the structure, controls, rotor mechanism, and other parts essential to a controlled landing of the rotorcraft, unless such parts are protected in accordance

with the provisions of § 6.384. All 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 rotorcraft by means of fire walls, shrouds, or other equivalent means. In complying with the provisions of this paragraph, account shall be taken of the probable path of a fire as affected by the air flow in normal flight and in autorotation. (See also § 6.486.)

(b) 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 rotorcraft.

(c) All openings in the fire wall or shroud shall be sealed with close fitting fireproof grommets, bushings, or firewall fittings.

(d) Fire walls and shrouds shall be constructed of fireproof material and shall be protected against corrosion. § 6.484

Engine cowling and engine compartment covering.

(a) Cowling or engine compartment covering shall be constructed and supported so as to make it capable of resisting all vibration, inertia, and air loads to which it would be subjected in operation.

(b) Provision shall be made to permit rapid and complete drainage of all portions of the cowling or engine compartment in all normal ground and flight attitudes. Drains shall not discharge in locations which might cause a fire hazard.

(c) Cowling or engine compartment covering shall be constructed of fireresistant material.

(d) Those portions of the cowling or engine compartment covering which would be subjected to high temperatures due to their proximity to exhaust system parts or exhaust gas impingement shall be constructed of fireproof material. § 6.485 Lines and fittings.

(a) All lines and fittings carrying flammable fluids in areas subject to engine fire conditions shall be fire resistant, except as otherwise provided in this section. If flexible hose is used, the assembly of hose and end fittings shall be of an approved type. The provisions of this paragraph shall not apply to those lines and fittings which form an integral part of the engine.

(b) Vent and drain lines and their fittings shall be subject to the provisions of paragraph (a) of this section unless a failure of such line or fitting will not result in, or add to, a fire hazard.

[Amdt. 6-4, 24 F.R. 7074, Sept. 1, 1959]

§ 6.486 Flammable fluids.

(a) Fuel tanks shall be isolated from the engine by a fire wall or shroud. On all rotorcraft having engines of more than 900 cu. in. displacement, oil tanks and other flammable fluid tanks shall be similarly isolated unless the fluid contained, the design of the system, the materials used in the tank, the shutoff means, all connections, lines, and controls are such as to provide an equally high degree of safety.

(b) Not less than one-half inch of clear air space shall be provided between any tank and the isolating fire wall or shroud, unless other equivalent means are used to protect against heat transfer from the engine compartment to the flammable fluid.

Subpart F-Equipment

(c) A magnetic direction indicator. (See § 6.612 (c).)

§ 6.604 Powerplant instruments.

(See § 6.613 for installation requirements.)

(a) Carburetor air temperature indicator for each engine equipped with a preheater which is capable of providing a heat rise in excess of 60° F.

(b) Cylinder head temperature indicator for each air-cooled engine or rotorcraft equipped with cooling shutters. In the case of rotorcraft which do not have cooling shutters, an indicator shall be provided if compliance with the provisions of § 6.451 is demonstrated in a condition other than the most critical cooling flight condition.

(c) Fuel pressure indicator for each engine (if pump-fed engines are used).

(d) Fuel quantity indicator for each tank. (See § 6.420(a).)

(e) Manifold pressure indicator for each engine (if altitude engines are used).

(f) Oil temperature warning device to indicate when the oil temperature exceeds a safe value in each main rotor drive gearbox (including those gearboxes essential to rotor phasing) having an oil system independent of the engine oil system.

(g) Oil pressure warning device to indicate when the oil pressure falls below a safe value in each pressure lubricated main rotor drive gearbox (including those gearboxes essential to rotor phasing) having an oil system independent of the engine oil system.

(h) Oil pressure indicator for each engine.

(i) Oil quantity indicator for each oil tank. (See 6.613(d).)

(j) Oil temperature indicator for each engine.

(k) Tachometer to indicate engine rpm and rotor rpm for the main rotor, or for each main rotor, the speed of

which can vary appreciably with respect to another main rotor.

[Amdt. 6-4, 24 F.R. 7074, Sept. 1, 1959] § 6.605 Miscellaneous equipment. There shall be installed:

(a) Approved seats for all occupants. (See 6.355.)

(b) Approved safety belts for all occupants. (See § 6.643.)

(c) A master switch arrangement. (See §§ 6.623 and 6.624.)

(d) A source (s) of electrical energy (see §§ 6.620 through 6.622) where such electrical energy is necessary for operation of the rotorcraft.

(e) Electrical protective devices. (See § 6.625.)

§ 6.606 Equipment, systems, and in

stallations.

(a) Functioning and reliability. All equipment, systems, and installations, the functioning of which is necessary in showing compliance with the regulations in this subchapter, shall be designed and installed to insure that they will perform their intended function reliably under all reasonably foreseeable operating conditions.

(b) Hazards. All equipment, systems, and installations shall be designed to safeguard against hazards to the rotorcraft in the event of their malfunctioning or failure.

[Amdt. 64, 24 F.R. 7074, Sept. 1, 1959]

§ 6.612 Flight and navigational instru

ments.

(a) Air-speed indicating system. The air-speed indicating system shall be so installed that the air-speed indicator shall indicate true air speed at sea level under standard conditions to within an allowable installational error of not more than plus or minus 3 percent of the calibrated air speed or 5 mph, whichever is greater. The calibration shall be made in flight at all forward speeds of 10 mph or over. The allowable installation error shall not be exceeded at any forward speed of 20 mph and over. The allowable installation error shall not be exceeded at any forward speed above 80 percent of the climb-out speed. (See § 6.732.)

(b) Static air-vent system. All instruments provided with static air case connections shall be so vented that the influence of rotorcraft speed, the opening and closing of windows, air-flow variation, moisture, or other foreign matter will not seriously affect their accuracy.

(c) Magnetic direction indicator. The magnetic direction indicator shall be so installed that its accuracy shall not be excessively affected by the rotorcraft's vibration or magnetic fields. After the direction indicator has been compensated, the installation shall be such that the deviation in level flight does not exceed 10° on any heading. A suitable calibration placard shall be provided as specified in § 6.733.

[21 F.R. 10291, Dec. 22, 1956, as amended by Amdt. 6-4, 24 F.R. 7074, Sept. 1, 1959]

§ 6.613 Powerplant instruments.

(a) Instrument lines. Instrument lines shall comply with the provisions of § 6.425. In addition, instrument lines carrying flammable fluids or gases under pressure shall be provided with restricted orifices or equivalent safety devices at the source of the pressure to prevent the escape of excessive fluid or gas in case of line failure.

(b) Fuel quantity indicator. Fuel quantity indicators shall be calibrated to read zero during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply as defined by § 6.421. (See also § 6.736.)

(c) Fuel flowmeter system. When a flowmeter system is installed, the metering component shall include a means for by-passing the fuel supply in the event