Gas turbine engine assembly and methods of assembling same

1. A method for assembling a gas turbine engine, said method comprising:

providing a low-pressure turbine that rotates in a single direction; and

coupling a counter-rotating fan assembly including a first fan assembly and a second fan assembly to the low-pressure turbine such that the first fan assembly is rotatable in a first direction and the second fan assembly is rotatable in a second direction that is opposite the first direction, wherein a single drive shaft is coupled between the low-pressure turbine and the first fan assembly, and wherein a gearbox is coupled between the single drive shaft and the second fan assembly such that the first fan assembly is rotatable in the first direction at a first rotational speed and the second fan assembly is rotatable in the second direction at a second rotational speed that is different than the first rotational speed.

2. A method in accordance with claim 1 further comprising positioning the second fan assembly axially aft of the first fan assembly.

3. A method in accordance with claim 1 wherein said coupling a counter-rotating fan assembly including a first fan assembly and a second fan assembly to the low-pressure turbine comprises coupling the first fan assembly and the second fan assembly to the low-pressure turbine such that the second rotational speed is approximately one-half of the first rotational speed.

4. A method in accordance with claim 1 further comprising coupling a booster compressor to the second fan assembly such that the booster compressor rotates at the second rotational speed.

5. A method in accordance with claim 1 further comprising positioning the gearbox within an engine sump.

6. A turbine engine assembly comprising:

a low-pressure turbine that rotates in a single direction;

a counter-rotating fan assembly coupled to said low-pressure turbine, said counter-rotating fan assembly comprising a first fan assembly configured to rotate in a first direction and a second fan assembly configured to rotate in a second direction that is opposite the first direction;

a single drive shaft coupled between said low-pressure turbine and said first fan assembly; and

a gearbox coupled between said shaft and said second fan assembly such that said first fan assembly is rotatable in the first direction at a first rotational speed and said second fan assembly is rotatable in the second direction at a second rotational speed that is different than the first rotational speed.

7. A turbine engine assembly in accordance with claim 6 wherein said second fan assembly is positioned axially aft of said first fan assembly.

8. A turbine engine assembly in accordance with claim 6 wherein said second fan assembly is configured to rotate at the second rotational speed such that the second rotational speed is approximately one-half of the first rotational speed.

9. A turbine engine assembly in accordance with claim 6 wherein said gearbox has a gear ratio that is approximately equal to 3.5 to 1 such that the second rotational speed is less than the first rotational speed.

10. A turbine engine assembly in accordance with claim 6 further comprising a booster compressor coupled to said second fan assembly such that said booster compressor is configured to rotate in the second direction and at the second rotational speed.

11. A turbine engine assembly in accordance with claim 6 wherein said gearbox is coupled within an engine sump.