Redundant electro-hydraulic servo valve (EHSV) control in a fuel metering system

A fuel metering system for a combustion system having a first combustor and a second combustor, comprising:

• a first fuel metering system configured to supply fuel to the first combustor, the first fuel metering system having a first electro-hydraulic servo valve (EHSV) fluidly coupled to a first system fuel metering valve (FMV) through a transfer system;
• and
• a second fuel metering system configured to supply fuel to the second combustor, the second fuel metering system having a second electro-hydraulic servo valve (EHSV) fluidly coupled to a second fuel metering valve (FMV) and to the first fuel metering valve (FMV) through the transfer system;
• and
• wherein the transfer system includes a fuel transfer valve having a multi-land piston configured to provide control pressures from the first EHSV to the first FMV to control positioning thereof during a normal mode of operation, and to provide control pressures from the second EHSV to the first FMV to control positioning thereof during a backup mode of operation.

A method of metering fuel for a multi-stage combustion system having a main combustion stage and at least one secondary combustion stage, comprising the steps of:

• controlling a position of a main system fuel metering valve (FMV) via a main electro-hydraulic servo valve (EHSV) during a normal mode of operation;
• controlling a position of a secondary system fuel metering valve (FMV) via a secondary electro-hydraulic servo valve (EHSV) during the normal mode of operation;
• and
• controlling a position of the main system fuel metering valve (FMV) via the secondary electro-hydraulic servo valve (EHSV) during a backup mode of operation.