Federal Aviation Administration, DOT § 25.1093

(2) The air for proper fuel metering ture of 30 F., each airplane with alti- and mixture distribution with the in- tude engines using— duction system valves in any position. (1) Conventional venturi carburetors (b) Each reciprocating engine must have a preheater that can provide a have an alternate air source that pre- heat rise of 120 F. with the engine at 60 vents the entry of rain, ice, or any percent of maximum continuous power; other foreign matter. or (c) Air intakes may not open within (2) Carburetors tending to reduce the the cowling, unless— probability of ice formation has a pre- (1) That part of the cowling is iso- heater that can provide a heat rise of lated from the engine accessory section 100 °F. with the engine at 60 percent of by means of a fireproof diaphragm; or (2) For reciprocating engines, there maximum continuous power. are means to prevent the emergence of (b) Turbine engines. (1) Each turbine backfire flames. engine must operate throughout the (d) For turbine engine powered air- flight power range of the engine (in- planes and airplanes incorporating aux- cluding idling), without the accumula- iliary power units— tion of ice on the engine, inlet system (1) There must be means to prevent components, or airframe components hazardous quantities of fuel leakage or that would adversely affect engine op- overflow from drains, vents, or other eration or cause a serious loss of power components of flammable fluid systems or thrust— from entering the engine or auxiliary (i) Under the icing conditions speci- power unit intake system; and fied in appendix C, and (2) The airplane must be designed to (ii) In falling and blowing snow with- prevent water or slush on the runway, in the limitations established for the taxiway, or other airport operating airplane for such operation. surfaces from being directed into the (2) Each turbine engine must idle for engine or auxiliary power unit air inlet 30 minutes on the ground, with the air ducts in hazardous quantities, and the bleed available for engine icing protec- air inlet ducts must be located or pro- tion at its critical condition, without tected so as to minimize the ingestion of foreign matter during takeoff, land- adverse effect, in an atmosphere that is ° ° ing, and taxiing. at a temperature between 15 and 30 F ¥ ° ¥ ° (e) If the engine induction system (between 9 and 1 C) and has a liq- contains parts or components that uid water content not less than 0.3 could be damaged by foreign objects grams per cubic meter in the form of entering the air inlet, it must be shown drops having a mean effective diameter by tests or, if appropriate, by analysis not less than 20 microns, followed by that the induction system design can momentary operation at takeoff power withstand the foreign object ingestion or thrust. During the 30 minutes of idle test conditions of §§ 33.76, 33.77 and operation, the engine may be run up 33.78(a)(1) of this chapter without fail- periodically to a moderate power or ure of parts or components that could thrust setting in a manner acceptable create a hazard. to the Administrator. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as (c) Supercharged reciprocating engines. amended by Amdt. 25–38, 41 FR 55467, Dec. 20, For each engine having a supercharger 1976; Amdt. 25–40, 42 FR 15043, Mar. 17, 1977; to pressurize the air before it enters Amdt. 25–57, 49 FR 6849, Feb. 23, 1984; Amdt. the carburetor, the heat rise in the air 25–100, 65 FR 55854, Sept. 14, 2000] caused by that supercharging at any § 25.1093 Induction system icing pro- altitude may be utilized in determining tection. compliance with paragraph (a) of this section if the heat rise utilized is that (a) Reciprocating engines. Each recip- rocating engine air induction system which will be available, automatically, must have means to prevent and elimi- nate icing. Unless this is done by other means, it must be shown that, in air free of visible moisture at a tempera-

491

VerDate Mar<15>2010 11:30 Mar 22, 2012 Jkt 226044 PO 00000 Frm 00501 Fmt 8010 Sfmt 8010 Y:\SGML\226044.XXX 226044 pmangrum on DSK3VPTVN1PROD with CFR § 25.1101 14 CFR Ch. I (1–1–12 Edition)

for the applicable altitude and oper- and entering any other compartment ating condition because of super- or area of the airplane in which a haz- charging. ard would be created resulting from the entry of hot gases. The materials used [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25–38, 41 FR 55467, Dec. 20, to form the remainder of the induction 1976; Amdt. 25–40, 42 FR 15043, Mar. 17, 1977; system duct and plenum chamber of Amdt. 25–57, 49 FR 6849, Feb. 23, 1984; Amdt. the auxiliary power unit must be capa- 25–72, 55 FR 29785, July 20, 1990] ble of resisting the maximum heat con- ditions likely to occur. § 25.1101 Carburetor air preheater de- (f) Each auxiliary power unit induc- sign. tion system duct must be constructed Each carburetor air preheater must of materials that will not absorb or be designed and constructed to— trap hazardous quantities of flammable (a) Ensure ventilation of the pre- fluids that could be ignited in the heater when the engine is operated in event of a surge or reverse flow condi- cold air; tion. (b) Allow inspection of the exhaust [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as manifold parts that it surrounds; and amended by Amdt. 25–46, 43 FR 50597, Oct. 30, (c) Allow inspection of critical parts 1978] of the preheater itself. § 25.1105 Induction system screens. § 25.1103 Induction system ducts and If induction system screens are air duct systems. used— (a) Each induction system duct up- (a) Each screen must be upstream of stream of the first stage of the engine the carburetor; supercharger and of the auxiliary (b) No screen may be in any part of power unit compressor must have a the induction system that is the only drain to prevent the hazardous accu- passage through which air can reach mulation of fuel and moisture in the the engine, unless it can be deiced by ground attitude. No drain may dis- heated air; charge where it might cause a fire haz- (c) No screen may be deiced by alco- ard. hol alone; and (b) Each induction system duct must (d) It must be impossible for fuel to be— strike any screen. (1) Strong enough to prevent induc- tion system failures resulting from § 25.1107 Inter-coolers and after-cool- normal backfire conditions; and ers. (2) Fire-resistant if it is in any fire Each inter-cooler and after-cooler zone for which a fire-extinguishing sys- must be able to withstand any vibra- tem is required, except that ducts for tion, inertia, and air pressure load to auxiliary power units must be fireproof which it would be subjected in oper- within the auxiliary power unit fire ation. zone. (c) Each duct connected to compo- EXHAUST SYSTEM nents between which relative motion could exist must have means for flexi- § 25.1121 General. bility. For powerplant and auxiliary power (d) For turbine engine and auxiliary unit installations the following apply: power unit bleed air duct systems, no (a) Each exhaust system must ensure hazard may result if a duct failure oc- safe disposal of exhaust gases without curs at any point between the air duct fire hazard or carbon monoxide con- source and the airplane unit served by tamination in any personnel compart- the air. ment. For test purposes, any accept- (e) Each auxiliary power unit induc- able carbon monoxide detection meth- tion system duct must be fireproof for od may be used to show the absence of a sufficient distance upstream of the carbon monoxide. auxiliary power unit compartment to (b) Each exhaust system part with a prevent hot gas reverse flow from burn- surface hot enough to ignite flammable ing through auxiliary power unit ducts fluids or vapors must be located or

492

VerDate Mar<15>2010 11:30 Mar 22, 2012 Jkt 226044 PO 00000 Frm 00502 Fmt 8010 Sfmt 8010 Y:\SGML\226044.XXX 226044 pmangrum on DSK3VPTVN1PROD with CFR