Fire-wall construction

This regulation establishes construction standards for firewalls and shrouds that separate engine compartments from the rest of the aircraft in Part 121 operations (scheduled air carriers). The firewall must prevent hazardous amounts of air, fluids, or flames from passing through to other airplane areas. Any openings must be sealed with close-fitting fireproof grommets, bushings, or fittings—you can't just leave gaps. The entire firewall must be made of fireproof material and protected against corrosion.

In practice, this creates a critical fire barrier that contains engine fires and prevents them from spreading to passenger cabins, fuel tanks, or flight control systems. This is essential for passenger safety and crew survivability in the event of an engine fire. The corrosion protection requirement ensures the firewall maintains its integrity throughout the aircraft's service life, since a corroded firewall could fail when needed most.

*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.*