A propulsion system for an aircraft comprises a gas turbine engine; a plurality of fuel tanks arranged to contain different fuels to be used to power the gas turbine engine, wherein the fuels have different calorific values; and a fuel manager. The fuel manager is arranged to store information on the fuel contained in each fuel tank and to control fuel input to the gas turbine engine in operation by selection of a specific fuel or fuel combination from one or more of the plurality of fuel tanks based on thrust demand of the gas turbine engine such that a fuel with a lower calorific value is supplied to the gas turbine engine at lower thrust demand.

A propulsion system for an aircraft comprises a gas turbine engine; a plurality of fuel tanks arranged to contain different fuels to be used to power the gas turbine engine, wherein the fuels have different calorific values; and a fuel manager. The fuel manager is arranged to store information on the fuel contained in each fuel tank and to control fuel input to the gas turbine engine in operation by selection of a specific fuel or fuel combination from one or more of the plurality of fuel tanks based on thrust demand of the gas turbine engine such that a fuel with a lower calorific value is supplied to the gas turbine engine at lower thrust demand.

A VTOL aircraft system includes a first unit having a cockpit, at least one propeller, at least two landing legs and at least two locking mechanisms. A second unit has a housing with a base portion, a first unit engaging portion, and at least two lock mechanism-engaging structure, each corresponding to one of the at least two locking mechanisms of the first unit. The housing of the second unit defines at least one interior cavity with at least one cargo area, a central passage providing access between the first and second unit, and a fuel cell configured around the central passage.

A VTOL aircraft system includes a first unit having a cockpit, at least one propeller, at least two landing legs and at least two locking mechanisms. A second unit has a housing with a base portion, a first unit engaging portion, and at least two lock mechanism-engaging structure, each corresponding to one of the at least two locking mechanisms of the first unit. The housing of the second unit defines at least one interior cavity with at least one cargo area, a central passage providing access between the first and second unit, and a fuel cell configured around the central passage.

In order to enlarge a tank volume of a hydrogen powered aircraft, an aircraft tank for storing cryogenic H.sub.2 is configured as a non-circular dorsal tank. The aircraft tank may be configured as a conformal fuel tank fitted to an outer contour of an aircraft fuselage. Further, an aircraft is provided with such an aircraft tank.

In order to enlarge a tank volume of a hydrogen powered aircraft, an aircraft tank for storing cryogenic H.sub.2 is configured as a non-circular dorsal tank. The aircraft tank may be configured as a conformal fuel tank fitted to an outer contour of an aircraft fuselage. Further, an aircraft is provided with such an aircraft tank.

Aircraft having at least one propulsion unit supplied with hydrogen by at least one hydrogen tank, and having at least one thrust reversal system including at least one actuator. The aircraft can include at least one means for storing or transporting the residual hydrogen of the propulsion unit, a fuel cell disposed in the hydrogen power source and supplied with hydrogen by the at least one means for storing the residual hydrogen, and a hydrogen thrust reverser actuation system. The thrust reverser actuation system can include a hydrogen thrust reverser actuation controller and a hydrogen primary power unit with a fuel cell supplied with hydrogen and powering the at least one thrust reverser actuator.

Aircraft having at least one propulsion unit supplied with hydrogen by at least one hydrogen tank, and having at least one thrust reversal system including at least one actuator. The aircraft can include at least one means for storing or transporting the residual hydrogen of the propulsion unit, a fuel cell disposed in the hydrogen power source and supplied with hydrogen by the at least one means for storing the residual hydrogen, and a hydrogen thrust reverser actuation system. The thrust reverser actuation system can include a hydrogen thrust reverser actuation controller and a hydrogen primary power unit with a fuel cell supplied with hydrogen and powering the at least one thrust reverser actuator.

A gas turbine engine includes a hydrogen fuel delivery assembly configured to deliver a hydrogen fuel flow, a compressor section configured to compress air flowing therethrough to provide a compressed air flow, and a combustor including a combustion chamber having a burner length and a burner dome height. The combustion chamber is configured to combust a mixture of the hydrogen fuel flow and the compressed air flow. The combustion chamber can be characterized by a combustor size rating between one inch and seven inches. In more detail, the combustion chamber can be characterized by the combustor size rating between one inch and seven inches at a core air flow parameter between two and one half kN and sixty kN, in which the combustor size rating is a function of the core air flow parameter.