A gas turbine engine comprising: a fan ; a compressor section comprising a first and a second compressor ; a combustor in fluid communication with the compressor section ; a turbine section comprising a first and a second turbine in fluid communication with the combustor ; a first spool including a first shaft that interconnects the fan , the first compressor and the first turbine ; a second spool including a second shaft that interconnects the second compressor and the second turbine ; and further comprising: a bleed system configured to receive bleed air from the compressor section , the bleed system comprising a first inlet duct configured to receive bleed air from an upstream location (L1) of the compressor section , a second inlet duct configured to receive bleed air from a downstream location (L2) of the compressor section a common duct into which the first inlet duct and the second inlet duct merge and a heat exchanger arranged in receiving communication with the common duct , wherein the second inlet duct includes a flow-control valve configured to selectively open and close flow from the compressor section through the second inlet duct and the first inlet duct includes a check valve , and the common duct includes a pressure-control valve ; characterized in that : the first shaft is connected to the fan through a gear assembly of a fan drive gear system to drive the fan at lower speed than the first spool , the gear assembly being an epicyclic gear train; the upstream location (L1) is a high pressure compressor stage of the compressor section ; and the downstream location (L2) is a diffuser stage of the compressor section . a fan ; a compressor section comprising a first and a second compressor ; a combustor in fluid communication with the compressor section ; a turbine section comprising a first and a second turbine in fluid communication with the combustor ; a first spool including a first shaft that interconnects the fan , the first compressor and the first turbine ; a second spool including a second shaft that interconnects the second compressor and the second turbine ; and further comprising: a bleed system configured to receive bleed air from the compressor section , the bleed system comprising a first inlet duct configured to receive bleed air from an upstream location (L1) of the compressor section , a second inlet duct configured to receive bleed air from a downstream location (L2) of the compressor section a common duct into which the first inlet duct and the second inlet duct merge and a heat exchanger arranged in receiving communication with the common duct , wherein the second inlet duct includes a flow-control valve configured to selectively open and close flow from the compressor section through the second inlet duct and the first inlet duct includes a check valve , and the common duct includes a pressure-control valve ; characterized in that : the first shaft is connected to the fan through a gear assembly of a fan drive gear system to drive the fan at lower speed than the first spool , the gear assembly being an epicyclic gear train; the upstream location (L1) is a high pressure compressor stage of the compressor section ; and the downstream location (L2) is a diffuser stage of the compressor section . the first shaft is connected to the fan through a gear assembly of a fan drive gear system to drive the fan at lower speed than the first spool , the gear assembly being an epicyclic gear train; the upstream location (L1) is a high pressure compressor stage of the compressor section ; and the downstream location (L2) is a diffuser stage of the compressor section . <EOS>