Shutoff means

This regulation requires aircraft operating under Part 121 to have shutoff controls that can stop fuel, oil, deicing fluid, and other flammable liquids from flowing into fire zones around each engine. The goal is to starve potential fires of flammable materials.

These shutoff controls must work in coordination with other emergency procedures like feathering propellers, allowing the crew to quickly manage an engine fire. The shutoffs themselves must be located outside fire zones (where they won't be damaged by fire) and positioned to prevent inadvertent activation while remaining accessible for intentional use.

Importantly, the system must prevent flammable fluids from draining into fire zones even after shutdown, and the crew must be able to reopen the shutoffs if needed. Lines that are integral parts of the engine itself don't require separate shutoff capability, recognizing that the engine's own systems handle this function.

*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.*