Gear device

A gear arrangement for an aircraft, comprising

• a plurality of gear systems, each of the gear system comprising:
• an input shaft;
• an output shaft;
• an input stage epicyclic gear comprising an input stage sun that is configured to rotate and connected to the input shaft, an input stage carrier that is stationary, an input stage ring that is configured to rotate, and input stage planetary gears supported by the input stage carrier and disposed between the input stage sun and input stage ring;
• and
• an output stage epicyclic gear comprising an output stage sun that is rotationally fixed to the input stage sun, an output stage carrier that is configured to rotate and connected directly or indirectly to the output shaft, an output stage ring that is rotationally fixed to the input stage ring, and output stage planetary gears supported by the output stage carrier and disposed between the output stage sun and output stage ring;
• wherein the input stage epicyclic gear and the output stage epicyclic gear are arranged concentrically with each other such that the input and output stage suns are concentric with each other, the input and output stage carriers are concentric with each other, and the input and output stage rings are concentric with each other;
• and
• a first fixed carrier train ratio of the input stage epicyclic gear and a second fixed carrier train ratio of the output stage epicyclic gear are configured such that when the input shaft rotates at a first speed, the input and output stage suns rotate together at the first speed, the input and output stage rings rotate together at a second speed, and the output stage carrier rotates at a third speed that is less than the first speed,
• whereby the output shaft rotates slower than the input shaft, and when the output shaft is connected directly to the output stage carrier, the output shaft rotates at the third speed,
• wherein the plurality of gear systems are connected to one another in series, wherein the input shaft is connected to the input stage sun of a first one of the gear systems and the output shaft is connected to the output stage carrier of a last one of the gear systems, wherein each of the gear systems is configured to reduce rotational speed and increase torque relative to a previous one of the gear systems so that, in operation, the output shaft rotates at a reduced speed relative to the input shaft and delivers greater torque than the input shaft.