A dual pump fuel supply system for an aircraft engine, the dual pump fuel supply system including: a high pressure supply, a bypass return, a low pressure return, wherein the high pressure supply and the bypass return are coupled in use to a fuel metering unit that is configured to supply a portion of the fuel supply to an engine and to return a bypass flow of the fuel supply to the low pressure return, a first pump having a first high pressure output and a first low pressure supply that is coupled to the low pressure return, wherein the first pump is coupled to the high pressure supply to the fuel metering unit; a second pump having a second high pressure output and a second low pressure supply that is coupled to the low pressure return, the second pump also having a second pump bypass that is coupled to the second low pressure supply, and a switching system for use with the dual pump fuel supply system, the switching system comprising: means for sensing the bypass flow from the fuel metering unit, means, operatively coupled to the means for sensing the bypass flow from the fuel metering unit, for controlling a pressurization of the second pump; and means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump, characterized in that the means for sensing the bypass flow from the fuel metering unit includes: a sensing valve having a sensing port coupled to the bypass return from the fuel metering unit, a return port coupled to the low pressure return, and a sensing valve valving member positioned there between, the sensing valve further including: a position port, a pressure reduction port, and a pressure addition port, wherein a differential pressure between the sensing port and the return port controls a position of the sensing valve valving member, and wherein the position of the sensing valve valving member selectively couples one of the pressure reduction port or the pressure addition port to the position port. a high pressure supply, a bypass return, a low pressure return, wherein the high pressure supply and the bypass return are coupled in use to a fuel metering unit that is configured to supply a portion of the fuel supply to an engine and to return a bypass flow of the fuel supply to the low pressure return, a first pump having a first high pressure output and a first low pressure supply that is coupled to the low pressure return, wherein the first pump is coupled to the high pressure supply to the fuel metering unit; a second pump having a second high pressure output and a second low pressure supply that is coupled to the low pressure return, the second pump also having a second pump bypass that is coupled to the second low pressure supply, and a switching system for use with the dual pump fuel supply system, the switching system comprising: means for sensing the bypass flow from the fuel metering unit, means, operatively coupled to the means for sensing the bypass flow from the fuel metering unit, for controlling a pressurization of the second pump; and means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump, characterized in that the means for sensing the bypass flow from the fuel metering unit includes: a sensing valve having a sensing port coupled to the bypass return from the fuel metering unit, a return port coupled to the low pressure return, and a sensing valve valving member positioned there between, the sensing valve further including: a position port, a pressure reduction port, and a pressure addition port, wherein a differential pressure between the sensing port and the return port controls a position of the sensing valve valving member, and wherein the position of the sensing valve valving member selectively couples one of the pressure reduction port or the pressure addition port to the position port. means for sensing the bypass flow from the fuel metering unit, means, operatively coupled to the means for sensing the bypass flow from the fuel metering unit, for controlling a pressurization of the second pump; and means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump, a sensing valve having a sensing port coupled to the bypass return from the fuel metering unit, a return port coupled to the low pressure return, and a sensing valve valving member positioned there between, the sensing valve further including: a position port, a pressure reduction port, and a pressure addition port, a position port, a pressure reduction port, and a pressure addition port, wherein a differential pressure between the sensing port and the return port controls a position of the sensing valve valving member, and wherein the position of the sensing valve valving member selectively couples one of the pressure reduction port or the pressure addition port to the position port.