Hybrid transmission on propeller gearbox

1. A gearbox assembly for a gas turbine engine comprising:

a first planetary gear set comprising a sun gear, a planet gear, and a ring gear, the sun gear configured for connection to a first drive shaft of the gas turbine engine and the ring gear configured for connection to a second drive shaft of the gas turbine engine; and

an electric machine assembly comprising a second planetary gear set, an input, and an electric machine, the electric machine comprising a rotor and a stator fixedly positioned to the gearbox assembly, the input of the electric machine assembly coupled to the first planetary gear set, and the rotor of the electric machine coupled to the input of the electric machine assembly across the second planetary gear set.

2. The gearbox assembly of claim 1 , wherein the first planetary gear set further comprises a planet gear carrier, wherein the planet gear is rotatably coupled to the planet gear carrier, wherein the planet gear carrier is fixedly positioned within the gearbox assembly, and wherein the input of the electric machine assembly is coupled to the ring gear of the first planetary gear set.

3. The gearbox assembly of claim 1 , wherein the sun gear, the planet gear, and the ring gear of the first planetary gear set are configured as a first sun gear, a first planet gear, and a first ring gear, wherein the second planetary gear set comprises a second sun gear, a second planet gear, and a second ring gear, wherein the input of the electric machine assembly is coupled to the second planet gear of the second planetary gear set.

4. The gearbox assembly of claim 3 , wherein the rotor of the electric machine of the electric machine assembly is coupled to the second sun gear of the second planetary gear set.

5. The gearbox assembly of claim 4 , wherein the second ring gear is fixedly positioned within the gearbox assembly.

6. The gearbox assembly of claim 1 , wherein the input of the electric machine assembly is coupled to the ring gear of the first planetary gear set, wherein the planet gear of the first planetary gear set is a compound planet gear comprising a first stage and a second stage, wherein the first stage is engaged with the sun gear of the first planetary gear set, and wherein the second stage is engaged with to the ring gear of the first planetary gear set.

7. The gearbox assembly of claim 1 , wherein the electric machine is arranged in an axial flux configuration.

8. The gearbox assembly of claim 1 , wherein the electric machine is arranged in a radial flux configuration.

9. The gearbox assembly of claim 8 , wherein the gearbox assembly defines a radial direction, and wherein the rotor is located inward of the stator along the radial direction.

10. The gearbox assembly of claim 8 , wherein the gearbox assembly defines a radial direction, and wherein the rotor is located outward of the stator along the radial direction.

11. The gearbox assembly of claim 1 , further comprising:

a gearbox assembly casing extending between a forward end and an aft end;

a first bearing assembly located at the aft end for rotatably mounting the gearbox assembly casing to the first drive shaft of the gas turbine engine at the aft end of the gearbox assembly casing; and

a second bearing assembly located at the forward end for rotatably mounting the gearbox assembly casing to the second drive shaft of the gas turbine engine at the forward end of the gearbox assembly casing.

12. The gearbox assembly of claim 1 , further comprising:

a gearbox assembly casing, wherein the stator of the electric machine is fixedly within the gearbox assembly casing of the gearbox assembly.

13. The gearbox assembly of claim 1 , wherein the input of the electric machine assembly is directly coupled to the ring gear of the first planetary gear set.