§ 4b.460 General. (a) The engine air induction system shall permit supplying the proper quantity of air to the engine under all conditions of operation.
(b) The induction system shall provide air for proper fuel metering and mixture distribution with the induction system valves in any position.
(c) Each engine shall be provided with an alternate air source.
(d) Air intakes shall not open within the cowling, unless that portion of the cowling is isolated from the engine accessory section by means of a fireproof diaphragm, or unless provision is made to prevent the emergence of backfire flames.
(e) Alternate air intakes shall be so located as to preclude the entrance of rain, ice, or any other foreign matter.
§ 4b.461 Induction system de-icing and anti-icing provisions—(a) General. The engine air induction system shall incorporate means for the prevention and elimination of ice accumulations.
(b) Heat rise. Unless it is demonstrated that other means will accomplish the intent of paragraph (a) of this section, compliance with the following heat-rise provisions shall be demonstrated in air free of visible moisture at a temperature of 30° F.
(1) Airplanes equipped with altitude engines employing conventional venturi carburetors shall have a preheater capable of providing a heat rise of 120° F. when the engine is operating at 60 percent of its maximum continuous power.
(2) Airplanes 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. when the engine is operating at 60 percent of its maximum continuous power.
§ 4b.462 Carburetor air preheater design. Carburetor air preheaters shall incorporate the following provisions.
(a) Means shall be provided to assure ventilation of the preheater when the engine is being operated with cold air.
(b) The preheater shall be constructed to permit inspection of exhaust manifold parts which it surrounds and also to permit inspection of critical portions of the preheater itself.
§ 4b.463 Induction system ducts. Induction system ducts shall incorporate the following provisions.
(a) Induction system ducts ahead of the first stage of the supercharger shall be provided with drains to prevent hazardous accumulations of fuel and moisture in the ground attitude. The drains shall not discharge in locations which might cause a fire hazard.
(b) Sufficient strength shall be incorporated in the ducts to prevent induction system failures resulting from normal backfire conditions.
(c) Ducts which are connected to components of the airplane between which relative motion could exist shall incorporate provisions for flexibility.
(d) Induction system ducts within any fire zone for which a fire-extinguishing system is required shall be of fire-resistant construction.
§ 4b.464 Induction system screens. If induction system screens are employed, they shall comply with the following provisions:
(a) Screens shall be located upstream from the carburetor.
(b) Screens shall not be located in portions of the induction system which constitute the only passage through which air can reach the engine, unless the screen is so located that it can be de-iced by heated air.
(c) De-icing of induction system screens by means of alcohol alone shall not be acceptable.
(d) It shall not be possible for fuel to impinge upon the screens.
§ 4b.465 Carburetor air cooling. Installations employing two-stage superchargers shall be provided with means to maintain the air temperature at the inlet to the carburetor at or below the maximum established value. The demonstration of this provision shall be accomplished in accordance with § 4b.451.
§ 4b.466 Inter-coolers and after-coolers. Inter-coolers and after-coolers shall be capable of withstanding without failure all vibration, inertia, and air pressure loads to which they would be subjected in operation.
§ 4b.467 Exhaust system and installation
components—(a) General. (1) The exhaust system shall be constructed and arranged to assure the safe disposal of exhaust gases without the existence of a fire hazard or carbon monoxide contamination of air in personnel compartments.
(2) Unless appropriate precautions are taken, exhaust system parts shall not be located in hazardous proximity to portions of any system carrying flammable fluids or vapors nor shall they be located under portions of such systems where the latter could be subject to leakage.
(3) All airplane components upon which hot exhaust gases might impinge, or which could be subjected to high temperatures due to proximity to exhaust system parts, shall be constructed of fireproof material. All exhaust system components shall be separated by means of fireproof shields from adjacent portions of the airplane which are outside the engine compartment.
(4) Exhaust gases shall not discharge in a manner to cause a fire hazard with respect to any flammable fluid vent or drain.
(5) Exhaust gases shall not discharge at a location which will cause a glare seriously affecting pilot visibility at night.
(6) All exhaust system components shall be
ventilated to prevent the existence of points of excessively high temperature.
(7) Exhaust shrouds shall be ventilated or insulated to avoid during normal operation a temperature sufficiently high to ignite any flammable fluids or vapors external to the shrouds.
(b) Exhaust piping. (1) Exhaust piping shall be constructed of material resistant to heat and corrosion, and shall incorporate provisions to prevent failure due to expansion when heated to operating temperatures.
(2) Exhaust pipe shall be supported to withstand all vibration and inertia loads to which they would be subjected in operation.
(3) Portions of the exhaust piping which are connected to components between which relative motion could exist shall incorporate provisions for flexibility
(c) Exhaust heat exchangers. (1) Exhaust heat exchangers shall be constructed and installed to assure their ability to withstand without failure all vibration, inertia, and other loads to which they would be subjected in operation.
(2) Heat exchangers shall be constructed of materials which are suitable for continued operation at high temperatures and which are resistant to corrosion due to elements contained in exhaust gases.
(3) Provision shall be made for the inspection of all critical portions of exhaust heat exchangers.
(4) Heat exchangers shall incorporate cooling provisions wherever they are subject to contact with exhaust gases.
(5) Heat exchangers or muffs shall incorporate no stagnant areas or liquid traps which would increase the possibility of ignition of flammable fluids or vapors which might be present in case of failure or malfunctioning of components carrying flammable fluids.
(d) Exhaust heating of ventilating air. If an exhaust heat exchanger is used for heating ventilating air, a secondary heat exchanger shall be provided between the primary exhaust gas heat exchanger and the ventilating air system, unless it is demonstrated that other means used preclude harmful contamination of the ventilating air.
(e) Exhaust driven turbo-superchargers. (1) Exhaust driven turbines shall be of an approved type or shall be shown to be suitable for the particular application. They shall be installed and supported to assure their safe operation between normal inspection and overhaul periods.
(2) Provision for expansion and flexibility shall be made between exhaust conduits and the turbine.
(3) Provision shall be made for lubrication of the turbine and for cooling of those turbine parts where the temperatures are critical.
(4) Means shall be provided so that, in the event of malfunctioning of the normal turbo-supercharger control system, the turbine speed will not be greater than its maximum allowable value. The components provided for this purpose shall be independent of the normal
turbo-supercharger controls with the exception of the waste gate operating components themselves.