US Patent 11279225 Fault-tolerant fuel isolation from engine firebay

Fuel isolation systems, apparatuses and methods are described. In some embodiments, a system comprises a fuel tank, a fuel pump, an engine, a firewall, a fuel line from the fuel tank to the engine, a connector coupled inline with the fuel line on a cold side of the fuel line, a normally closed valve coupled to the connector, an air feed line coupled to an ullage of the fuel tank and to the valve. In the event of an engine fire condition, a control unit outputs signaling to turn off the fuel pump and open the valve to introduce air from the ullage into the fuel line. The introduced air provides a siphon break in the fuel line such that the fuel cannot be siphoned and the only fuel that can pass the firewall is the remaining fuel in the fuel line downstream of the connector and the introduced air.