NOVELTY - The operating method involves supplying hydrocarbon fuel to the combustor during high power and low power conditions, and injecting gaseous hydrogen to the combustor (24) of a gas turbine engine (10) at least during low power conditions in response to a gas turbine power output level. The mass flow of hydrogen injected to the combustor can be increased or decreased when decreasing or increasing turbine power output. The hydrogen injection is stopped when changing from low power condition to high power condition or started when changing from high power condition to low power condition.    USE - Operating method for gas turbine engine for aircraft (Claimed) e.g. airplane. Can also be used for gas turbine engine for aviation, aeronautics, marine applications, and industrial power production, as well as industrial gas turbine engines operated at different output power levels for compensating fluctuation in electrical power supply from regenerative energy sources e.g. wind, solar, water energy.    ADVANTAGE - Hydrogen is injected into combustor of gas turbine engine especially during low power conditions, accelerating combustion kinetics while also allowing for use of small sized combustor even for low turbine engine power conditions without risk of unburnt hydrocarbon and carbon monoxide emissions or creating negative effects for low turbine engine power. Small combustor size also provides benefits for high turbine engine power conditions including minimized nitrogen oxide emissions. Hydrogen injection is stopped at high power output and mid power output operations to minimize hydrogen consumption. Low carbon monoxide, low unburnt hydrocarbons and low nitrogen oxide from engine emissions makes gas turbine engine suited for aviation. Engine can run at low power while taxiing, reducing gaseous emissions at e.g. airports.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a power supplying device or system for aeronautics; and    (2) an aircraft.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of an aviation gas turbine engine with a turbine engine control system.    Gas turbine engine (10)    By-pass duct (16)    Compressor (18)    Turbine (20)    Combustor (24)