(a) Reciprocating engines. Each reciprocating engine air
induction system must have means to prevent and eliminate icing. Unless
this is done by other means, it must be shown that, in air free of visible
moisture at a temperature of 30 °F., and with the engines at 60 percent of
maximum continuous power --
(1) Each rotorcraft with sea level engines using conventional venturi
carburetors has a preheater that can provide a heat rise of 90 °F.;
(2) Each rotorcraft with sea level engines using carburetors tending to
prevent icing has a preheater that can provide a heat rise of 70 °F.;
(3) Each rotorcraft with altitude engines using conventional venturi
carburetors has a preheater that can provide a heat rise of 120 °F.; and
(4) Each rotorcraft with altitude engines using carburetors tending to
prevent icing has a preheater that can provide a heat rise of 100 °F.
(b) Turbine engines. (1) It must be shown that each turbine
engine and its air inlet system can operate throughout the flight power
range of the engine (including idling) --
(i) Without accumulating ice on engine or inlet system components that
would adversely affect engine operation or cause a serious loss of power
under the icing conditions specified in appendix C of this Part; and
(ii) In snow, both falling and blowing, without adverse effect on
engine operation, within the limitations established for the rotorcraft.
(2) Each turbine engine must idle for 30 minutes on the ground, with
the air bleed available for engine icing protection at its critical
condition, without adverse effect, in an atmosphere that is at a
temperature between 15° and 30 °F (between −9° and −1 °C) and has a liquid
water content not less than 0.3 grams per cubic meter in the form of drops
having a mean effective diameter not less than 20 microns, followed by
momentary operation at takeoff power or thrust. During the 30 minutes of
idle operation, the engine may be run up periodically to a moderate power
or thrust setting in a manner acceptable to the Administrator.
(c) Supercharged reciprocating engines. For each engine having a
supercharger to pressurize the air before it enters the carburetor, the
heat rise in the air caused by that supercharging at any altitude may be
utilized in determining compliance with paragraph (a) of this section if
the heat rise utilized is that which will be available, automatically, for
the applicable altitude and operation condition because of supercharging. (Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49 U.S.C. 1354(a),
1421, and 1423; sec. 6(c), 49 U.S.C. 1655 (c))