A gas turbine engine for an aircraft comprising: an engine core comprising at least one turbine (17, 19), at least one compressor (14, 15) and at least one shaft (26, 27) connecting the turbine (17, 19) to the compressor (14, 15); a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a gearbox that receives an input from the shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the shaft; a first oil circuit, a second oil circuit and at least a third oil circuit; the first oil circuit, the second oil circuit and the third oil circuit are fluidly coupled with at least one inlet (48, 49, 56) of the gearbox as well as with at least one outlet (50, 90, 91, 94) of the gearbox; the first oil circuit and the second oil circuit each including at least one pump (57, 58, 59, 60); the third oil circuit including a pump; and the at least one outlet (50, 90, 91, 94) of the gearbox including a device configured, when in use, to direct oil from the gearbox to the first oil circuit and/or to the second oil circuit and/or to the third oil circuit when the feeding to the gearbox is exceeding a predefined oil flow rate, or is deviating at least one operational value corresponding with that oil flow rate, and further configured, when in use, to direct the oil from the gearbox to the third oil circuit when the feeding to the gearbox is less than or equal to the predefined flow rate or is less than or equal to at least one corresponding operational value or is greater than or equal to at least one further corresponding operational value; wherein: the second oil circuit is configured to direct oil from an oil tank to a turbomachinery of the gas turbine engine; the pumps (57, 58, 59, 60) of the first oil circuit and the second oil circuit are driven by the shaft; and the pump of the third oil circuit is driven by the fan. an engine core comprising at least one turbine (17, 19), at least one compressor (14, 15) and at least one shaft (26, 27) connecting the turbine (17, 19) to the compressor (14, 15); a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a gearbox that receives an input from the shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the shaft; a first oil circuit, a second oil circuit and at least a third oil circuit; the first oil circuit, the second oil circuit and the third oil circuit are fluidly coupled with at least one inlet (48, 49, 56) of the gearbox as well as with at least one outlet (50, 90, 91, 94) of the gearbox; the first oil circuit and the second oil circuit each including at least one pump (57, 58, 59, 60); the third oil circuit including a pump; and the at least one outlet (50, 90, 91, 94) of the gearbox including a device configured, when in use, to direct oil from the gearbox to the first oil circuit and/or to the second oil circuit and/or to the third oil circuit when the feeding to the gearbox is exceeding a predefined oil flow rate, or is deviating at least one operational value corresponding with that oil flow rate, and further configured, when in use, to direct the oil from the gearbox to the third oil circuit when the feeding to the gearbox is less than or equal to the predefined flow rate or is less than or equal to at least one corresponding operational value or is greater than or equal to at least one further corresponding operational value; wherein: the second oil circuit is configured to direct oil from an oil tank to a turbomachinery of the gas turbine engine; the pumps (57, 58, 59, 60) of the first oil circuit and the second oil circuit are driven by the shaft; and the pump of the third oil circuit is driven by the fan. the second oil circuit is configured to direct oil from an oil tank to a turbomachinery of the gas turbine engine; the pumps (57, 58, 59, 60) of the first oil circuit and the second oil circuit are driven by the shaft; and the pump of the third oil circuit is driven by the fan.