Materials for compartment interiors

This regulation sets fire safety standards for airplane interior materials, focusing on two scenarios:

First, it addresses airplanes modified under a specific special rule (SFAR 41) that increased their maximum takeoff weight above 12,500 pounds. These aircraft must meet certain interior material flammability standards from 1978 within one year of receiving their modified airworthiness certificate.

Second, and more commonly applicable, it requires thermal and acoustic insulation in transport category airplanes to meet modern flame propagation standards. For planes built before September 2, 2005, this applies only when replacing blanket-type insulation or insulation around air ducts after that date. For planes manufactured after September 2, 2005, all fuselage insulation must meet these stricter fire-resistance requirements from the start.

These rules ensure that interior materials, particularly insulation that could fuel cabin fires, meet enhanced safety standards either when aircraft are significantly modified or as newer planes enter service.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*