RTCA DO-160 – Section 26.0 – Fire and Flammability

This section defines test conditions and procedure for Fire and Flammability resistance.
Fire and Flammability tests apply to equipment installed on fixed wing propeller driven
aircraft, fixed-wing turbojet aircraft, turbofan aircraft, prop fan aircraft, and helicopters.
These tests are applicable for equipment:

    Mounted in pressurized zones
    Mounted in fire zones
    Mounted in non-pressurized, non fire zones

 
Category A: Fireproof
Intended for equipment installed in fire zone which must function during the first five minutes of fire and which must keep its safety functions for at least fifteen minutes. For fluid handling components, there shall be no leakage to support a flame after the burner has been removed (wetting or droplet that self extinguishes may be acceptable). For air handling components there shall be no leakage that may additionally feed the fire. Equipment shall remain firmly attached to the mounting. The fireproof procedure shall be applied. Test will be performed on equipment in the operating mode.
Category B: Fire Resistant
Intended for equipment installed in fire zone which must not cause a hazardous condition during five minutes of fire without structural degradation. For fluid handling components there shall be no leakage to support a flame after the burner has been removed (wetting or droplet that self extinguishes may be acceptable). For air handling components there shall be no leakage that may additionally feed the fire. In general any leakage of continued burning of the test article at the end of the five minutes would be considered a test failure unless it can be shown that there is not a significant increase in the overall fire hazard. An example of this would be if the fire extinguishing equipment is capable of extinguishing the residual flame. The fire resistant procedure shall be applied. Test will be performed on equipment in the operating mode.
Category C: Flammability
Applies to enclosures housing electronics and non-metallic material, component parts, sub-assemblies installed in pressurized or non-pressurized zones and non-fire zones. Test to be performed on equipment in a non-operating mode. The purpose of this test is to check the non-propagation of the flame in the case where ignition would appear inside or outside of the equipment. Tests will be performed on specimens of material. The flammability procedure shall be applied.
Note: If all materials used in the construction of the equipment can be shown to meet the equivalent vertical and horizontal flammability tests herein, either through composition or previous testing, this test is not required.
Testing is not necessary on enclosures housing electronic or non-metallic material if the following apply:

    The enclosures is constructed of metal (metal finish that is non flammable), on all sides, and has no vent holes
    The enclosures is constructed of metal (metal finish that is non flammable) on five sides and one side is constructed of glass polycarbonate (display) that has met the 12 second vertical test, and has no vent holes.


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Overview
This section outlines test conditions and procedures for fire and flammability resistance of equipment installed in various zones of fixed-wing and rotary-wing aircraft.

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Application of Fire and Flammability Tests
Fire and flammability tests apply to equipment installed in:

• Pressurized zones
• Fire zones
• Non-pressurized, non-fire zones

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Categories of Fire and Flammability Tests

Category A: Fireproof
Purpose: Applies to equipment installed in fire zones that must function during the first 5 minutes of fire and maintain safety functions for at least 15 minutes.

• Fluid handling components: No leakage to support flames after the burner is removed. Self-extinguishing droplets are acceptable.
• Air handling components: No leakage that feeds the fire.
• Attachment: Equipment must remain securely mounted.
• Operating Mode: Test performed while equipment is operating.

Failure Criteria: Any leakage that sustains a flame or compromises attachment integrity is considered a failure.

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Category B: Fire Resistant
Purpose: Applies to equipment in fire zones that must avoid hazardous conditions during 5 minutes of fire without structural degradation.

• Fluid handling components: Same as Category A.
• Air handling components: Same as Category A.
• Residual Fire: Leakage or burning at the end of 5 minutes results in failure unless extinguishing equipment mitigates the hazard.
• Operating Mode: Test performed while equipment is operating.

Failure Criteria: Structural degradation or sustained burning increases overall fire risk.

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Category C: Flammability
Purpose: Tests non-metallic materials, electronic housings, and sub-assemblies for flame propagation in pressurized/non-pressurized and non-fire zones.

• Mode: Tests conducted with equipment in a non-operating mode.
• Focus: Evaluates whether flames propagate inside or outside the equipment.

Exemptions:

• Testing is not required if the enclosure is entirely metallic, non-flammable, and has no vent holes.
• Testing is not required if the enclosure is metallic on five sides with one glass/polycarbonate side (display) passing the 12-second vertical flammability test, and has no vent holes.

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Testing Overview
Category A & B: Fire Zones

• Focus: Flame resistance and ability to avoid exacerbating fire hazards.
• Mode: Equipment tested in operating mode.

Category C: Non-Fire Zones

• Focus: Non-propagation of flames.
• Mode: Equipment tested in non-operating mode.

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General Notes:

• If materials meet equivalent vertical and horizontal flammability standards, additional testing may not be necessary.
• Proper material composition or prior certifications can exempt testing requirements.