Hybrid drive for gas turbine engine

1. A gas turbine engine comprising:

a fan drive turbine for selectively driving a fan rotor;

a drive shaft between said fan drive turbine and said fan rotor including a clutch, and an electric motor; and

said electric motor being positioned such that it is not downstream of a flow path relative to said fan drive turbine, said electric motor and said drive shaft of said fan drive turbine driving said fan rotor through a common shaft.

2. The gas turbine engine as set forth in claim 1 , wherein said fan drive turbine drives a shaft extending through a core engine duct delivering air into a compressor rotor, and said shaft driving a bevel gear to in turn drive said fan rotor.

3. The gas turbine engine set forth in claim 2 , wherein said electric motor is positioned radially outwardly of said core engine duct.

4. The gas turbine engine as set forth in claim 3 , wherein said clutch is also positioned radially outwardly of said core engine duct.

5. The gas turbine engine as set forth in claim 1 , wherein said fan drive turbine rotor also driving a compressor rotor.

6. The gas turbine engine as set forth in claim 1 , wherein there are three turbine rotors, wherein an upstream and intermediate turbine rotor each drive a compressor rotor, and a downstream of said three turbine rotors being said fan drive turbine.

7. The gas turbine engine as set forth in claim 1 , wherein a control may open said clutch when an associated aircraft is at cruise altitude.

8. The gas turbine engine as set forth in claim 1 , wherein said motor is operated when the associated aircraft is at cruise altitude.

9. The gas turbine engine as set forth in claim 1 , wherein an axially outer location of said gas turbine engine is defined as the location of said fan rotor, and said electric motor being positioned axially intermediate said fan rotor and said combustor.

10. The gas turbine engine as set forth in claim 7 , wherein said clutch is closed at least when the associated aircraft is at take-off conditions.

11. A method of operating a gas turbine engine comprising the steps of:

driving a turbine rotor through a clutch to drive an associated fan rotor, and providing an electric motor for selectively driving said fan motor;

driving said fan rotor with said clutch closed by said gas turbine engine when an associated aircraft is at a relatively high power condition; and

opening said clutch, stopping operation of said gas turbine engine, and driving said fan rotor through said electric motor when the associated aircraft is at a low power condition, and further including the step of positioning said electric motor such that it is not downstream of a flow path for products of combustion having passed downstream of a fan drive turbine rotor, that is driving said fan rotor, said electric motor and said drive shaft of said fan drive turbine driving said fan rotor through a common shaft.

12. The method as set forth in claim 11 , wherein said fan drive turbine driving a shaft extending through a core engine duct delivering air into a compressor rotor, and said shaft driving a bevel gear to in turn drive said fan rotor.

13. The method set forth in claim 12 , wherein said electric motor is positioned radially outwardly of said core engine duct.

14. The method as set forth in claim 13 , wherein said clutch is also positioned radially outwardly of said core engine duct.

15. The method as set forth in claim 11 , wherein the fan drive turbine rotor also driving a compressor rotor.

16. The method as set forth in claim 11 , wherein there are three turbine rotors, wherein an upstream and intermediate turbine rotor each drive the compressor rotor, and a downstream of said three turbine rotors being said fan drive turbine rotor.

17. The method as set forth in claim 11 , wherein said clutch is opened when an associated aircraft is at cruise altitude.

18. The method as set forth in claim 11 , wherein said motor is operated when the associated aircraft is at cruise altitude.

19. The method as set forth in claim 11 , wherein an axially outer location of said gas turbine engine is defined as the location of said fan rotor, and said electric motor being positioned axially intermediate said fan rotor and said combustor.

20. The method as set forth in claim 17 , wherein said clutch is closed at least when the associated aircraft is at take-off conditions.

21. The gas turbine engine as set forth in claim 1 , wherein there are a plurality of fan rotors, and said fan drive turbine driving said plurality of fan rotors through a plurality of clutches, and each of said fan rotors being provided with an electric motor.

22. The gas turbine engine as set forth in claim 1 , wherein said drive shaft of said fan drive turbine driving a gear which is turn drives the gear associated with the second drive shaft, said clutch being positioned on said second drive shaft, and said second drive shaft driving another gear which in turn drives a gear to drive a shaft associated with said fan rotor, and said electric motor being positioned on said second drive shaft.