Patent ID: 8893466

Claim:
A fuel flow system for a gas turbine engine, the system comprising: a first pump in communication with a fuel source and a nozzle; a second pump in communication with the fuel source and the nozzle; an actuator in communication with the first pump; a metering valve disposed downstream of the first and second pumps; a bypass loop connected to the first pump and the second pump and configured to recycle excess fuel from the first pump and excess fuel from the second pump back to inlets of the first and second pumps; a dual window valve comprising: a housing having a high pressure side, a low pressure side, a first inlet connected to the first pump, a first outlet connected to the bypass loop, a first flow passage connected between the first inlet and the first outlet, a second inlet connected to the second pump, a second outlet connected to the bypass loop, and a second flow passage connected between the second inlet and the second outlet; a spool slidably received within the housing and having a high pressure end proximate the high pressure side of the housing, a low pressure end proximate the low pressure side of the housing, a first metering edge, and a second metering edge; wherein the first inlet of the housing and the first metering edge of the spool define a first window; wherein the second inlet of the housing and the second metering edge of the spool define a second window; and a spring disposed between the low pressure side of the housing and the low pressure end of the spool; a first port formed in the high pressure side of the housing and configured to receive a pressure signal from upstream of the metering valve; and a second port formed in the low pressure side of the housing and configured to receive a pressure signal from downstream of the metering valve; and wherein the metering valve is in communication with the first pump, and wherein the metering valve is in communication with the second pump when the second window is restricted.