Aircraft comprising an engine with a bleed air port suitable for letting air from the engine flowing into a bleed air duct, a ram air inlet flap, suitable for letting air from the outside of the aircraft flowing into a ram air duct, a heat exchanging pack comprising an energy recovering module with a hot side comprising a hot side inlet and a hot side outlet, and a cold side, comprising a cold side inlet and a cold side outlet, the hot side being in thermal contact with the cold side by means of a conversion means, thus causing a heat exchange, a secondary heat exchanger with a hot side inlet, a hot side outlet, a cold side inlet and a cold side outlet, and a compressor coupled with a turbine, the compressor and turbine having an inlet and an outlet, such that the hot side inlet of the energy recovering module is in fluid communication with the bleed air duct, the cold side inlet of the energy recovering module is in fluid communication with the ram air duct, the hot side outlet of the energy recovering module is in fluid communication with the compressor inlet, the compressor outlet is in fluid communication with the hot side inlet of the secondary heat exchanger, the hot side outlet of the secondary heat exchanger is in fluid communication with the turbine inlet, the cold side inlet of the secondary heat exchanger is in fluid communication with the ram air duct, wherein the conversion means is adapted to generate electrical energy out from the heat exchange that takes place in the energy recovering module between the hot side and the cold side, wherein the conversion means comprises: a first closed circuit housing a first work fluid, an evaporator comprised in the closed circuit, with an inlet and an outlet, a circuit expander comprised in the closed circuit, with an inlet and an outlet, a condenser comprised in the closed circuit, with an inlet and an outlet, and a circuit compressor comprised in the closed circuit, with an inlet and an outlet, wherein the first work fluid in the evaporator is in thermal contact with the hot side of the energy recovering module, the outlet of the evaporator being in fluid connection with the inlet of the circuit expander, and the outlet of the expander being in fluid contact with the inlet of the circuit condenser, and wherein the first work fluid in the circuit condenser is in thermal contact with the cold side of the energy recovering module, the outlet of the circuit condenser being in fluid connection with the inlet of the circuit compressor, and the outlet of the circuit compressor being in fluid contact with the inlet of the circuit evaporator, therefore some work being obtained by the first work fluid when passing through the expander. an engine with a bleed air port suitable for letting air from the engine flowing into a bleed air duct, a ram air inlet flap, suitable for letting air from the outside of the aircraft flowing into a ram air duct, a heat exchanging pack comprising an energy recovering module with a hot side comprising a hot side inlet and a hot side outlet, and a cold side, comprising a cold side inlet and a cold side outlet, the hot side being in thermal contact with the cold side by means of a conversion means, thus causing a heat exchange, a secondary heat exchanger with a hot side inlet, a hot side outlet, a cold side inlet and a cold side outlet, and a compressor coupled with a turbine, the compressor and turbine having an inlet and an outlet, such that the hot side inlet of the energy recovering module is in fluid communication with the bleed air duct, the cold side inlet of the energy recovering module is in fluid communication with the ram air duct, the hot side outlet of the energy recovering module is in fluid communication with the compressor inlet, the compressor outlet is in fluid communication with the hot side inlet of the secondary heat exchanger, the hot side outlet of the secondary heat exchanger is in fluid communication with the turbine inlet, the cold side inlet of the secondary heat exchanger is in fluid communication with the ram air duct, an energy recovering module with a hot side comprising a hot side inlet and a hot side outlet, and a cold side, comprising a cold side inlet and a cold side outlet, the hot side being in thermal contact with the cold side by means of a conversion means, thus causing a heat exchange, a secondary heat exchanger with a hot side inlet, a hot side outlet, a cold side inlet and a cold side outlet, and a compressor coupled with a turbine, the compressor and turbine having an inlet and an outlet, such that the hot side inlet of the energy recovering module is in fluid communication with the bleed air duct, the cold side inlet of the energy recovering module is in fluid communication with the ram air duct, the hot side outlet of the energy recovering module is in fluid communication with the compressor inlet, the compressor outlet is in fluid communication with the hot side inlet of the secondary heat exchanger, the hot side outlet of the secondary heat exchanger is in fluid communication with the turbine inlet, the cold side inlet of the secondary heat exchanger is in fluid communication with the ram air duct, a first closed circuit housing a first work fluid, an evaporator comprised in the closed circuit, with an inlet and an outlet, a circuit expander comprised in the closed circuit, with an inlet and an outlet, a condenser comprised in the closed circuit, with an inlet and an outlet, and a circuit compressor comprised in the closed circuit, with an inlet and an outlet,