Crewmember interphone system

This regulation requires Part 121 operators to install a crewmember interphone system on airplanes with more than 19 passenger seats. This system must work independently from the passenger PA system (though they can share some components like handsets) and enable two-way communication between the flight deck and all passenger compartments and galleys not on the main deck.

The system must be immediately accessible from two flight deck stations and at least one flight attendant station per cabin, operable within 10 seconds by flight attendants. On large turbojets, additional requirements apply: interphone stations must be positioned so flight attendants can observe all floor-level emergency exits, an alerting system must distinguish between normal and emergency calls, and ground crew must be able to communicate with the flight deck from an exterior station that's not visible from inside the aircraft.

This ensures reliable crew coordination during normal operations and emergencies.

*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.*