Alternate Wire Flammability Test Procedures For Small Wire

Alternate Wire Flammability Test Procedures For Small Wire Test Specimens Christopher Bresciano 3/20/06

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens • Code of Federal Regulations, 14 CFR 25. 869(a)(4) Fire protection: systems “Insulation on electrical wire and electrical cable installed in any area of the airplane must be self-extinguishing when tested in accordance with the applicable portions of part I, appendix F of this part. ”

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens 60 -Degree Electrical Wire Bunsen Burner Test Set-up

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens • The Code of Federal Regulations, Part 25, Part I of Appendix F states the following with regard to wire test specimens used in the 60 -Degree Bunsen Burner Test for Electric Wire: Appendix F, Part I(a)(3)(b)(7): “The upper end of the specimen must pass over a pulley or rod and must have an appropriate weight attached to it so that the specimen is held tautly throughout the flammability test. The test specimen span between lower clamp and upper pulley or rod must be 24 inches…” “Breaking of the wire test specimens is not considered a failure. ”

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens • The Aircraft Materials Fire Test Handbook, DOT/FAA/AR-00/12, states the following with regard to wire test specimens used in the 60 -Degree Bunsen Burner Test for Electric Wire: Section 4. 4. 2 - Specimen Length “The specimens will be cut to a length of 30 inches (762 mm). The specimen span between the lower clamp and upper pulley or rod will be 24 inches (610 mm). ” Section 4. 8. 4 - Wire Breakage “It will not be considered a failure if the wire breaks during the test. ”

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens • Small Part Exemption does not apply to electrical wire From Appendix F, Part I(a)(1)(v): “Except for small parts (such as knobs, handles, rollers, fasteners, clips, grommets, rub strips, pulleys, and small electrical parts) that would not contribute significantly to the propagation of a fire…”

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens This presents a problem when: • The wire test specimen will not fit in the test fixture (length is less than 30 inches (762 mm)) - AND/OR - • The wire test specimen breaks prior to completion of the wire flammability test (typically, 26 AWG or smaller)

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens This situation tends to occur when wire flammability testing is required for: • Line Replaceable Units (LRU’s) • In-Flight Entertainment System Equipment (IFE) • Handsets • Printers • Other miscellaneous small electronic equipment

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens Alternate Test Procedure for Wire Specimens that Do Not Fit in the Test Fixture (wire is less than 30 inches long) Attach an alternate wire retention device such that the wire specimen will maintain it’s proper orientation in the test fixture • Alligator clips attached to an appropriate length of wire can be used as an alternate wire retention device. • Attach a weight to the alternate wire retention device to keep the test specimen taut.

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens Wire Pulley or Rod Alternate Wire Retention Device (Alligator Clip) Weight Wire Specimen Alternate Wire Retention Device (Alligator Clip) Wire Clamp Alternate Test Set-up for Wire Specimens that Do Not Fit in the Test Fixture

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens Alternate Test Procedure for Wire Specimens that Break Prior to Completion of Wire Flammability Testing (wire is 26 AWG or smaller) Use Nickel Chromium Ribbon as an Alternate Wire Retention Device • Attach a nickel chromium ribbon in the test set-up using the same method for placing a wire specimen in the test fixture. • Attach a weight to keep the nickel chromium ribbon taut. Keep in mind that too heavy a weight will cause the ribbon to break under sufficient heat. • Attach the wire specimen to the nickel chromium ribbon using string ties (Dacron). Attach sting ties at least 3 inches away from the point of flame application, being careful to not interfere with the flame. The wire specimen should be adjacent and parallel to the ribbon. This should allow the flame to be applied to the wire specimen for the required time period.

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens Alternate Wire Retention Device (Nickel Chromium Ribbon) Pulley or Rod String Ties (Dacron) 3 inches Weight 3 inches Wire Specimen Clamp Alternate Test Set-up for Wire Specimens that Break

Alternate Wire Flammability Test Procedures for Small Wire Test Specimens Conclusion: • Alternate test procedures are necessary for wire specimens that are too small to fit in the 60 -Degree Bunsen Burner Wire Flammability Test fixture and for wire specimens that break prior to completion of wire flammability testing. Proposal: • Allow industry to submit alternate test procedures to FAA Tech Center for evaluation and approval. • Incorporate these proposed alternate test procedures into the Aircraft Materials Fire Test Handbook, DOT/FAA/AR-00/12.