Section 4 – Temperature and Altitude:

Equipment Categories

Category A1

Equipment installed  in controlled temperature and pressurized locations, on an aircraft within which
pressures are normally no lower than the altitude equivalent of l5,000 ft. This category can be used on equipment installed in temperature controlled but unpressurized locations on an aircraft that operates at altitudes no higher than 15,000 ft.

Category A2

Equipment installed in pressurized locations that have partially controlled temperature. Applicable pressure should be no lower than the equivalent of 15,000 ft.  This category may be considered equipment installed in unpressurized locations under partially controlled conditions, no lower than the altitude equivalent of 15,000 ft.

Category A3

Equipment installed in pressurized locations that have partially controlled temperature. Applicable pressure should be no lower than the equivalent of 15,000 ft, where the intended temperature range may be more severe that found in category A1 or Category A2.

Category A4

Equipment installed in a controlled temperature and pressurized location, no lower than the altitude equivalent of 15,000 ft. where the manufacturer declares temperature ranges different than from category A1. 

Category B1

Equipment installed in non-pressurized but controlled temperature locations with intended operating
altitudes up to 25,000 ft.

Category B2

Equipment installed in non-pressurized and non-controlled temperature locations with intended operating altitudes up to 25,000 ft.

Category B3

Equipment installed in a power plants compartment with intended operational altitudes up to 25,000 ft. 

Category B4

Equipment installed in non-pressurized locations with intended operational altitudes up to 25,000 ft , that have different temperature requirements than found under category B1 and category B2.

Category C1

Equipment installed in non-pressurized but controlled temperature locations with intended operating altitudes up to 35,000 ft.

Category C2

Equipment installed in non-pressurized and non-controlled temperature locations with intended operational altitudes up to 35,000 ft.

Category C3

Equipment installed in power plant compartments with intended operational  altitudes up to 35,000 ft.

Category C4

Equipment installed in non-pressurized locations operated at altitudes up to 35,000 ft, when the intended temperature requirements are outside the parameters established under Category C2 and C2. 

Category D1

Equipment installed in non-pressurized locations, and in a controlled temperature location with intended operational altitude up to 50,000 ft. 

Category D2

Equipment installed in non-pressurized and non-controlled temperature locations on an aircraft that is operated at altitudes up to 50,000 ft.

Category D3

Equipment installed in power plant locations with intended operational altitudes up to 50,000 ft .

Category E1

Equipment installed in non-pressurized locations and in a non-controlled temperature location with intended operational altitudes up to 70,000 ft.

Category E2

Equipment installed in power plant locations with intended operational  altitudes up to 70,000 ft.

Category F1

Equipment installed in non-pressurized locations, and in a controlled temperature location with intended operational altitude up to 55,000 ft .

Category F2

Equipment installed in non-pressurized locations, and in a non-controlled temperature location with intended operational altitude up to 55,000 ft .

Category F3

Equipment installed in power plant locations with intended operational  altitudes up to 55,000 ft.

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