CS 25 Flammability Considerations review by Sofema Aviation Services (SAS) www.sassofia.com
Introduction
- At the very core of flammability compliance for aircraft, interiors are regulation Section 25.853 and part 25, appendix F, part I, which details the test criteria.
- Section 25.855 is also relevant to interiors manufacturers who make products specifically for the cargo compartments of the aircraft.
Appendix F, part I, provides exact methods for the preparation of test samples, the configuration of the tests by product type, and the test result tolerances by product type.
The FAA Aircraft Materials Fire Test Handbook provides essential information on the various test methods and provides the appropriate test forms to be completed for each of the types of flammability tests.
Current testing is based on the FAR/CS 25, the FAA Fire Testing Handbook, and several Advisory Circulars namely:
- 25.853 Part I Test Criteria and Procedures for Showing Compliance with Sec. 25.853, or 25.855.
- 25.853 Part II Flammability of Seat Cushions.
- 25.855 Part III Test Method to Determine Flame Penetration Resistance of Cargo Compartment Liners.
- 25.853 Part IV Test Method to Determine the Heat Release Rate From Cabin Materials Exposed to Radiant Heat.
- 25.853 Part V Test Method to Determine the Smoke Emission Characteristics of Cabin Materials.
- 25.856 Part VI Test Method To Determine the Flammability and Flame Propagation Characteristics of Thermal/Acoustic Insulation Materials.
- 25.856 Part VII Test Method To Determine the Burn through Resistance of Thermal/Acoustic Insulation Materials.
Vertical Bunsen Burner Test FAR/CS 25.853
- APPENDIX F PART I (a)(1)(i)
o Ignition Time 60 sec Extinguishing time max. 15 sec
o Burn length max 15 cm (6 inch)
o Drip extinguishing time Max 3 sec
o Minimum Flame temperature 843°C
o Coupon size: 3”X12”
o Coupon Qty: 3 each (if fabric 6 each)
- APPENDIX F PART I (a)(1)(ii)
o Ignition Time12 sec Extinguishing time max. 15 sec
o Burn length max 20 cm (8 inch)
o Drip extinguishing time Max 5 sec
o Minimum Flame temperature 843°C
o Coupon size: 3”X12”
o Coupon Qty: 3 each (if fabric 6 each)
FAR 25.853 Small Part Definition
- 14 CFR §25.853(b-3), Amendment 25-32 Materials that are Exempt from Flammability Testing.
- Small parts that do not require flammability testing are defined by FAA regulations as knobs, handles, rollers, fasteners, clips, grommets, rub strips, pulleys, and small electrical parts.
- In addition, other components having sizes of 3.0″ H X 3.0″ W X 0.50″ T or less or a group of components that can fit inside a 2.0″ H X 2.0″ W X 2.0″ T cube are classified herein as small parts that would not contribute significantly to the propagation of a fire and therefore also do not require flammability testing.
Fire Containment Test FAR 25.853 (e)
Aircraft Materials Fire testing Handbook Chapter 10 Fire Containment Test of Waste Stowage Compartments These methods are intended for use in determining the fire containment capability of containers, carts, and compartments used to store combustible waste materials according to the requirements of FAR 25.853(e).
Fire Containment Test
FAR 25.853 (e)
- The Trash Container will be tested with paint, the fire extinguisher will be removed and all holes sealed with aluminum tape.
- Procedure and Materials:
o The lid will be hinged opened so that typical refuse can be placed in the container.
o The following mixture of combustibles shall be utilized: Eight (8) Paper Towels, 11×14 inches-40% by number Five (5) Paper Napkins, 12.5×13 inches-25% by number Four (4) Paper Drink Cups, 0.2 lt.-20% by number Two (2) Paper Drink Cups, 0.1 lt.-10% by number One (1) empty cigarette package.
Oil burner test for seat cushions
FAR/CS 25.853 F PART II 14CFR 25.853 Compartment Interiors
(a) Materials (including finishes or decorative surfaces applied to the materials).
(b) Must meet the applicable test criteria prescribed in part I of Appendix F of this Part, or other approved equivalent methods, regardless of the passenger capacity of the airplane.
(c) In addition to meeting the requirements of paragraph (a) of this section, seat cushions, except those on the flight crewmember seats, must meet the test requirements of Part II of appendix F of this Part, or other equivalent methods, regardless of the passenger capacity of the airplane.
FAR/CS 25.853 APPENDIX F PART II
- Average weight loss max. 10 %
- Burn length max. 43 cm (17 inches)
- Apply time 2 minutes
- Flame temperature Approx. 1000 °C
- Flame length Approx. 30 cm
- Coupon Qty (3 each seat and 3 each back cushion)
- Coupon sizes for seat cushion: 20”X18”
- Coupon sizes for back cushion: 25”X18”
Oil burner test for cargo liners
FAR/CS 25.855 Appendix F Part III Sec. 25.855 cargo or baggage compartments
- For each cargo and baggage compartment, the following apply:
o Ceiling and sidewall liner panels of Class C compartments must meet the test requirements of Part III of Appendix F of this part or other approved equivalent methods.
o All other materials used in the construction of the cargo or baggage compartment must meet the applicable test criteria prescribed in Part I of Appendix F of this part or other approved equivalent methods.
FAR/CS 25.855 APPENDIX F PART III (TEST METODE TO DETERMINE FLAME PENETRATION RESISTANCE OF CARGO COMPARTMENT LINERS)
- Flame penetration: There will be no flame penetration of any specimen within 5 minutes after application of the flame source.
- Peak temperature: The peak temperature measured at 4 inches above the upper surface of the horizontal test sample must not exceed 400°F.
- Apply time 5 minutes.
- Flame temperature Approx. 1700°F.
- Flame length Approx. 30 cm.
- Coupon Qty: 3 sets (sidewall or ceiling panel).
- Coupon size: 16” x 24”.
FAR/CS 25.855 Appendix F Part III Sec. 25.855 cargo or baggage compartments
Large storage compartments on the main passenger deck may be classified as Class B cargo compartments and therefore subject to further requirement. (e.g 45 degrees burn through the test)
Heat release rate: Smoke density Sec. 25.853 (d) – Compartment interiors
Interior ceiling and wall panels, partitions, galley structure, including carts and containers, cabinets, and cabin stowage compartment for airplanes with passenger capacities of 20 or more must meet the requirements for Heat Release Rate and Smoke Emission.
The interiors of cabinets and stowage compartments, cockpit, galleys, lavatories, crew rest quarters, or other not occupied areas need not meet the requirements, provided they are isolated from the main passenger cabin by doors that would be closed during taxi takeoff and landing (TT & L).
Heat release rate / Smoke density (quantity of heat transmitted through the panel)
FAR/CS 25.853 APPENDIX F, PART IV/V
- Total heat release max. 65 KW min/m2 at 2 min.
- Peak heat release max. 65 KW/m2.
- Smoke density max. 200 Ds/4 min.
- Apply time 5 minutes.
- Heating elements 3.5 W / cm2.
- 1 lower pilot burner.
- 1 upper pilot burner.
- Air inlet 40 l / s.
- Coupon size: for Heat release test 151 x 151 mm.
- Coupon Qty: 3 each.
- Coupon Size: for Smoke density test 75mm x 75mm.
- Coupon Qty: 3 each.
Heat and Smoke Release Exemption comply with 25.853(d) in the following cases:
Commercially operated and with a passenger capacity of 20 or more.
When an exemption to HR/SE is requested, the design must comply with the following:
- Limited to Private use only or if commercially operated limited to max 19 passengers.
- Evacuation of all occupants must be shown within 45 seconds.
Test Method To Determine the Flammability and Flame Propagation Characteristics of Thermal/Acoustic Insulation Materials.
Amendment 25-111 (68 FR 45046, July 31, 2003) added new fire protection requirements applicable to thermal/acoustic insulation materials.
Note: The term ‘thermal/acoustic’ means either thermal or acoustic or both.
The amendment added test requirements in parts VI and VII of Appendix F related to flame propagation and burn through penetration resistance, respectively.
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aviation, SAS blogs, CS 25, Flammability, FAA Aircraft Materials Fire Test Handbook, FAR/CS 25, FAR/CS 25.853, FAR 25.853, Fire Containment, FAR/CS 25.855, Thermal/Acoustic Insulation Materials
