CS 27.1093  Induction system icing protection

ED Decision 2003/15/RM

(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 –1°C (30°F) and with the engines at 75% of maximum continuous power:

(1)     Each rotorcraft with sea-level engines using conventional venturi carburettors has a preheater that can provide a heat rise of 50°C (90°F);

(2)     Each rotorcraft with sea-level engines using carburettors tending to prevent icing has a sheltered alternate source of air, and that the preheat supplied to the alternate air intake is not less than that provided by the engine cooling air downstream of the cylinders;

(3)     Each rotorcraft with altitude engines using conventional venturi carburettors has a preheater capable of providing a heat rise of 67°C (120°F); and

(4)     Each rotorcraft with altitude engines using carburettors tending to prevent icing has a preheater that can provide a heat rise of:

(i)      56°C (100°F); or

(ii)     If a fluid de-icing system is used, at least 22°C (40°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 CS-29; 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 –9°C and –1°C (15° and 30°F) and has a liquid water content not less than 0.3 grams per cubic metre in the form of drops having a mean effective diameter of not less than 20 microns, followed by momentary operation at take-off 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 Agency.

(c)      Supercharged reciprocating engines. For each engine having superchargers to pressurise the air before it enters the carburettor, the heat rise in the air caused by that supercharging at any altitude may be utilised in determining compliance with sub-paragraph (a) if the heat rise utilised is that which will be available, automatically, for the applicable altitude and operating condition because of supercharging.