An aircraft system comprising: a variable frequency, VF, bus configured to supply power to a portion of electrical loads of the aircraft system; and a constant frequency, CF, bus configured to supply power to a remaining portion of the electrical loads of the aircraft system; a gas turbine engine comprising: a compressor coupled to a first turbine through a high-pressure, HP, shaft extending between the compressor and the first turbine; a fan coupled to a second turbine through a low-pressure, LP, shaft extending between the fan and the second turbine and coaxial with the HP shaft; a CF electrical generator electrically coupled to said CF bus, said CF electrical generator configured to supply CF electrical energy to said CF electrical bus; a VF electrical generator electrically coupled to said VF bus, said VF electrical generator configured to draw a first amount of mechanical energy from the HP shaft; a constant speed mechanical drive assembly having an input and an output, the input mechanically coupled to the LP shaft, the output mechanically coupled to said CF electrical generator; and an accessory gearbox assembly having an input and an output, the input mechanically coupled to the HP shaft, the output mechanically coupled to said VF electrical generator; and means configured to, when the gas turbine engine system is operating at or near idle speed, maintain a minimum load on said LP shaft and said first amount of mechanical energy is minimised. a variable frequency, VF, bus configured to supply power to a portion of electrical loads of the aircraft system; and a constant frequency, CF, bus configured to supply power to a remaining portion of the electrical loads of the aircraft system; a gas turbine engine comprising: a compressor coupled to a first turbine through a high-pressure, HP, shaft extending between the compressor and the first turbine; a fan coupled to a second turbine through a low-pressure, LP, shaft extending between the fan and the second turbine and coaxial with the HP shaft; a CF electrical generator electrically coupled to said CF bus, said CF electrical generator configured to supply CF electrical energy to said CF electrical bus; a VF electrical generator electrically coupled to said VF bus, said VF electrical generator configured to draw a first amount of mechanical energy from the HP shaft; a constant speed mechanical drive assembly having an input and an output, the input mechanically coupled to the LP shaft, the output mechanically coupled to said CF electrical generator; and an accessory gearbox assembly having an input and an output, the input mechanically coupled to the HP shaft, the output mechanically coupled to said VF electrical generator; and a compressor coupled to a first turbine through a high-pressure, HP, shaft extending between the compressor and the first turbine; a fan coupled to a second turbine through a low-pressure, LP, shaft extending between the fan and the second turbine and coaxial with the HP shaft; a CF electrical generator electrically coupled to said CF bus, said CF electrical generator configured to supply CF electrical energy to said CF electrical bus; a VF electrical generator electrically coupled to said VF bus, said VF electrical generator configured to draw a first amount of mechanical energy from the HP shaft; a constant speed mechanical drive assembly having an input and an output, the input mechanically coupled to the LP shaft, the output mechanically coupled to said CF electrical generator; and an accessory gearbox assembly having an input and an output, the input mechanically coupled to the HP shaft, the output mechanically coupled to said VF electrical generator; and means configured to, when the gas turbine engine system is operating at or near idle speed, maintain a minimum load on said LP shaft and said first amount of mechanical energy is minimised.