ECO

An ECO, or engine cutoff, is a fuel shutoff valve in an aircraft's fuel system that interrupts fuel flow to one or more engines. The pilot operates it via a switch or lever in the cockpit, typically to shut down an engine intentionally during cruise, emergency procedures, or before landing. Unlike a magneto switch, which kills ignition, an ECO physically stops fuel delivery, forcing the engine to cease combustion within seconds.

Most aircraft have one ECO control per engine mounted on the center console or pedestal. Twin-engine planes carry two independent ECO switches; larger transports may have separate controls for each engine or separate fuel shutoff valves feeding individual engine fuel metering units. Older aircraft used cable-operated mechanical shutoffs; modern designs employ motorized solenoid valves that respond instantly to cockpit switches. Some systems incorporate a return-to-neutral gate or guard to prevent accidental activation during normal flight.

Pilots deploy the ECO during engine failure diagnosis, single-engine training flights, shutdown procedures, and emergency descent. On light aircraft, a malfunctioning engine might be isolated by pulling its ECO rather than attempting an air restart. In larger turbine-powered machines, the ECO cuts fuel faster than a throttle idle and is mandatory for any flameout scenario. During maintenance, mechanics use the ECO to test fuel shutoff function and confirm fuel system isolation before working on engine fuel components.

An ECO failure, either refusal to shut off or unintended closure in flight, ranks as a critical system defect. If an ECO valve sticks closed, fuel never reaches the engine and starting becomes impossible; if it sticks open during an intentional shutdown, the engine will not quit. These failures are discovered during ground runs and preflight checks, typically by observing engine response delay or fuel flow instrument readings. Contamination in the fuel system or corrosion of solenoid contacts are common culprits.

The term has military and civilian currency. Military aircraft use ECO controls, though the nomenclature varies slightly by airframe. Homebuilt aircraft and experimentals must have functional ECO systems to meet airworthiness standards. The ECO is distinct from firewall shutoff systems (which also cut fuel and electrical power to isolate a burning engine compartment) and from crossfeed shutoffs (which permit fuel transfer between tanks). Mechanics must verify ECO operation as part of annual inspections and after any fuel system work.