§29.859 Combustion heater fire protection

(a) Combustion heater fire zones. The following combustion heater fire zones m ust be protected against fire under the applicable provisions of CS 29.1181 to 29.1191, and CS 29.1195 to 29.1203: (1) The region surrounding any heater, if that region contains any flam mable fluid sy stem components (including the heater fuel sy stem), that could: (i) Be dam aged by heater malfunctioning; or (ii) Allow flammable fluids or vapours to reach the heater in case of leakage. (2) Each part of any ventilating air passage that: (i) Surrounds the combustion chamber; and (ii) Would not contain (without damage to other rotorcraft com ponents) any fire that may occur within the passage. (b) Ventilating air ducts. Each ventilating air duct passing through any fire zone m ust be fireproof. In addition – (1) Unless isolation is provided by fireproof valves or by equally effective means, the ventilating air duct downstream of each heater must be fireproof for a distance great enough to ensure that any fire originating in the heater can be contained in the duct; and (2) Each part of any ventilating duct passing through any region having a flammable fluid sy stem m ust be so constructed or isolated from that sy stem that the m alfunctioning of any component of that sy stem cannot introduce flammable fluids or vapours into the ventilating airstream. (c) Combustion air ducts. Each com bustion air duct must be fireproof for a distance great enough to prevent dam age from backfiring or reverse flame propagation. In addition: (1) No com bustion air duct may communicate with the ventilating airstream unless flames from backfires or reverse burning cannot enter the ventilating airstream under any operating condition, including reverse flow or m alfunction of the heater or its associated components; and (2) No combustion air duct m ay res trict the prompt relief of any backfire that, if so restricted, could cause heater failure. (d) Heater controls; general. There m ust be means to prevent the hazardous accum ulation of water or ice on or in any heater control component, control system tubing, or safety control. (e) Heater safety controls. For each com bustion heater, safety control means m ust be provided as follows: (1) Means independent of the com ponents provided for the norm al continuous control of air temperature, airflow, and fuel flow must be provided, for each heater, to autom atically shut off the ignition and fuel supply of that heater at a point rem ote from that heater when any of the following occurs: (i) The heat exchanger tem perature exceeds safe limits. (ii) The ventilating air tem perature exceeds safe limits. (iii) The combustion airflow becomes inadequate for safe operation. (iv) The ventilating airflow becom es inadequate for safe operation. (2) The m eans of com plying with sub-paragraph (e)(1) for any individual heater must: (i) Be independent of components serving any other heater whose heat output is essential for safe operation; and (ii) Keep the heater off until restarted by the crew. (3) There must be means to warn the crew when any heater whose heat output is essential for safe operation has been shut off by the autom atic means prescribed in sub-paragraph (e)(1). (f) Air intakes. Each com bustion and ventilating air intake m ust be where no flammable fluids or vapours can enter the heater sy stem under any operating condition: (1) During normal operation; or (2) As a result of the m alfunction of any other component. (g) Heater exhaust. Each heater exhaust sy stem must meet the requirements of CS 29.1121 and 29.1123. In addition: (1) Each exhaust shroud m ust be sealed so that no flam mable fluids or hazardous quantities of vapours can reach the exhaust systems through joints; and (2) No exhaust s ystem m ay res trict the prompt relief of any backfire that, if s o restricted, could cause heater failure. (h) Heater fuel systems. Each heater fuel system must m eet the powerplant fuel sy stem requirem ents affecting safe heater operation. Each heater fuel system com ponent in the ventilating airstream must be protected by shrouds so that no leakage from those components can enter the ventilating airstream. (i) Drains. There m ust be m eans for safe drainage of any fuel that might accumulate in the combustion chamber or the heat exchanger. In addition – (1) Each part of any drain that operates at high temperatures must be protected in the sam e manner as heater exhausts; and (2) Each drain m ust be protected against hazardous ice accum ulation under any operating condition.