Manifold select metering system

A manifold select metering system for switching a supply of metered fuel from a secondary fuel metering system to a primary fuel manifold from a secondary fuel manifold upon failure of a primary fuel metering system supplying the primary fuel manifold, comprising:

• a transfer electro-hydraulic servo valve (EHSV);
• an overspeed and shutoff valve (OSSV) fluidly coupled to the transfer EHSV;
• a discharge select valve (DSV) operatively coupled to the OSSV;
• a pressurizing valve configured to supply metered fuel from the primary fuel metering system to the primary fuel manifold;
• a first throttling valve positioned between the secondary fuel metering system and the primary fuel manifold;
• a second throttling valve positioned between the secondary fuel metering system and the secondary fuel manifold;
• and
• wherein the OSSV includes a piston configured to connect a transfer pressure to the pressurizing valve when commanded by the transfer EHSV to isolate the primary fuel metering system from the primary fuel manifold;
• wherein the piston is further configured to connect the transfer pressure to the DSV when commanded by the transfer EHSV to drive a multi-land piston of the DSV from a quiescent position to a commanded position to switch a throttling valve control pressure from the second throttling valve to the first throttling valve, and to switch a throttling valve shutoff pressure from the first throttling valve to the second throttling valve.

A method of providing prime reliability of a primary fuel manifold upon failure of a primary fuel metering system supplying metered fuel thereto, the method comprising the steps of:

• isolating the primary fuel metering system from the primary fuel manifold;
• isolating a secondary fuel metering system from a secondary fuel manifold;
• and
• connecting the secondary fuel metering system to the primary fuel manifold;
• wherein the step of isolating the primary fuel metering system from the primary fuel manifold comprises the step of closing a pressurizing valve fluidly coupling the primary fuel metering system to the primary fuel manifold,
• wherein the step of isolating a secondary fuel metering system from a secondary fuel manifold comprises the step of closing a first throttling valve fluidly coupling the secondary fuel metering system to the secondary fuel manifold, and
• wherein the step of connecting the secondary fuel metering system to the primary fuel manifold comprises the steps of:
• switching a throttling valve shutoff pressure from a second throttling valve fluidly coupling the secondary fuel metering system to the primary fuel manifold to the first throttling valve;
• and
• switching a throttling valve control pressure from the first throttling valve to the second throttling valve.