Section 4 – Temperature and Altitude:
Equipment Categories
Category A1
Equipment intended for installation in a controlled temperature and pressurized location, on an aircraft within which pressures are normally no lower than the altitude equivalent of l5,000 ft Mean Sea Level (MSL), is identified as Category A1. This category may also be applicable to equipment installed in temperature controlled but unpressurized locations on an aircraft that operates at altitudes no higher than 15,000 ft MSL.
Category A2
Equipment intended for installation in a partially controlled temperature but pressurized location on an aircraft within which the pressures are normally no lower than the altitude equivalent of 15,000 ft. This category may also be applicable to equipment installed in partially controlled temperature but unpressurized locations on an aircraft that operates at altitudes no higher than 15,000 ft
Category A3
Equipment intended for installation in a controlled or partially controlled temperature but pressurized location within an aircraft within which the pressures are normally no lower than the altitude equivalent of 15,000 ft , where the temperatures will be more severe than those for categories A1 and A2.
Category A4
Equipment intended for installation in a controlled temperature and pressurized location, on an Mean Sea Level (MSL), . This category may also be applicable to equipment installed in a temperature controlled but unpressurized locations on an aircraft that operates at altitudes no higher than 15,000ft.
Category B1
Equipment intended for installation in a non-pressurized but controlled temperature location in an aircraft that is operated at altitudes up to 25,000 ft
Category B2
Equipment intended for installation in non-pressurized and non-controlled temperature locations on an aircraft that is operated at altitudes up to 25,000 ft
Category B3
Equipment intended for installation in the power plan t compartment of an aircraft that is operated at altitudes up to 25,000 ft
Category B4
Equipment intended for installation in a non-pressurized location on an aircraft that is operated at altitudes up to 25,000 ft B2, is identified as Category B4.
Category C1
Equipment intended for installation in a non-pressuri zed but controlled temperature location in an aircraft that is operated at altitudes up to 35,0 00 ft
Category C2
Equipment intended for installation in non-pressurized and non-controlled temperature locations within an aircraft that is operated at altitudes up to 35,000 ft.
Category C3
Equipment intended for installation in the power plan t compartment of an aircraft that is operated at altitudes up to 35,000 ft
Category C4
Equipment intended for installation on a non-pressurized aircraft that is operated at altitudes up to 35,000 ft (, for which temperature requirements differ from C1 and C2.
Category D1
Equipment intended for installation in a non-pressurized but controlled temperature location on an aircraft that is operated at altitudes up to 50,000 ft .
Category D2
Equipment intended for installation in non-pressurized and non-controlled temperature locations on an aircraft that is operated at altitudes up to 50,000 ft
Category D3
Equipment intended for installation in the power plan t compartment of an aircraft that is operated at altitudes up to 50,000 ft .
Category E1
Equipment intended for installation in non-pressurized and non-controlled temperature locations on an aircraft that is operated at altitudes up to 70,000 ft
Category E2
Equipment intended for installation in the power plan t compartment of an aircraft that is operated at altitudes up to 70,000 ft
Category F1
Equipment intended for installation in non-pressuri zed but controlled temperature locations on an aircraft that is operated at altitudes up to 55,000 ft
Category F2
Equipment intended for installation in non-pressurized and non-controlled temperature locations on an aircraft that is operated at altitudes up to 55,000 ft
Category F3
Equipment intended for installation in the power plan t compartment of an aircraft that is operated at altitudes up to 55,000 ft
Operating High Temperature
Maximum levels that the equipment will be exposed to within the particular installation area, e.g. in an enclosed space behind an instrument panel, equipment racks, power plant areas, etc., under normal operating conditions.
Short-Time Operating Temperature
Start up conditions where equipment is turned on following a ground soak. It is expected that these temperature conditions will occur infrequently and be of short duration, since cooling or heating air circulation or other means of controlling temperature would be enabled concurrent with equipment operation.
Ground Survival Temperatures
Lowest and highest ground temperatures that the equipment is normally expected to be exposed to during aircraft storage or exposure to climatic extremes. The equipment is not expected to operate within specification limits at these temperatures but is expected to survive without damage.
In-Flight Loss of Cooling
This condition represents the failure of the external or internal system that normally provides dedicated cooling for the equipment. Certain equipment must survive for a limited time in the absence of cooling. Test requirements for this type of equipment shall be specified in the equipment performance specification
In Flight Loss of Cooling Categories
Category V – 30 minutes minimum
Category W – 90 minutes minimum
Category P – 180 minutes minimum
Category Y – 300 minutes minimum
Category Z – As defined in the equipment specification
Altitude, Decompression and Overpressure Tests
Category A
Category B
Category C
Category D
Category E