MIL-H-18325B(Aer)
3.18.3 Cabin Pressurization. - When installed in aircraft with cabin pressurization, the
ventilating air passages only of the heater shall be subjected to the increased Pressures
developed by the pressurizing system. The space within the heat exchanger shall be
subjected to the increased pressures developed by the pressurizing system. The space
within the heater combustion chamber and controls as well as the ignition and fuel systems
shall not be subjected to the pressures developed by the cabin pressurizing system.
Vapor Prevention - Provision shall be made to ventilate adequately and continuously
3.18.4
the compartments in which combustion-type heaters are installed in order to prevent the
accumulation of fuel vapors in the event of fuel leakage. Ventilation rate shall exceed
5 pounds of air per minute per 100,000 BTU per hour rated thermal capacity of the heater.
3.18.5
Fuel Pump - The heater fuel pump shall conform to Specification MIL-P-6992 (Aer).
Heating Equipment - Type II (Engine Exhaust)
3.19
3.19.1 Air Supply - Suitable means shall be provided to permit the flow of sufficient
air through the heat interchanger at all times to prevent premature failure due to
overheating. The valves used to control the flow of heated air shall be of such
construction and ruggedness as to preclude warpage or leakage for any reason during the
life of the heating system.
3.19.2 Secondary Exchange - If a secondary air-to-air exchanger is used, means
shall be provided for regulating the flow of the air being heated in the secondary
exchanger. The design and construction of primary exhaust-to-air heat exchanger shall be
sucha that vibration or expansion and contraction due to rapid heating and cooling shall
not cause cracking of the heat exchanger of the exhaust stack.
3.20
Heating Equipment - Type III (Engine Bleed Air)
3.20.1 Type III Heating Equipment shall be of either the bleed air convection or ram
air convection type.
3.20.2 Temperature regulation of cabin inlet air shall be l emhd by a suitable
air-to-air heat exchanger and by-pass system.
Heating Equipment - Type IV(Electric)
3.21
3.21.1 Type IV Electric Heating Equipment shall conform to the requirements of
Specification MIL-E-7080.
De-ice and Anti-ice - When the heating system used for de-icing the wings and tail
3.22
surfaces is combiined with the cabin heating system, that part pertaining to the thermal
de-icing and anti-icing shall conform to the requirements of SpecificatiOn MIL-T-18607 (Aer).
33.23 Ducting - All flexible air ducting Shall conform to the requirements of Specification
MIL-H-8796 (ASG)
3.24 Marking - Fuel Lines to the heater shall be marked in accordance with AN standard
Drawing and 10375.
3.25 Drawings and Data - Complete drawings and data on the entire installation shall
be submitted. The drawings shall include a schematic layout of the system as installed
in the airplane, showing the size and type of heating units and heat exchangers, the size
and location of all ducting, the complete heating} ventilating, defogging, defrosting
and anti-icing systems and fuel and/or electrical schematic diagram if applicable. The
data should include calculations of the heat required, expected temperature gradients,
principles of operation, method and location of controls, wiring, diagrams, wieght
analysis, estimated fuel consumbtion and electric power consumption.
9
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