Ram air turbine shaft whirl damper

1. A ram air turbine (RAT), comprising:

a housing;

a turbine shaft configured to connect to one or more turbine blades and be turned by the one or more blades, the turbine shaft disposed in the housing to rotate relative to the housing along a rotational axis;

a first bearing and a second bearing mounted between the turbine shaft and the housing to allow the turbine shaft to rotate relative to the housing; and

a whirl reduction system configured to dampen or eliminate whirl around the rotational axis, wherein the whirl reduction system includes:

a third bearing between the housing the turbine shaft; and

a spring connected to the third bearing and to the housing to provide a spring force to the turbine shaft to bias the turbine shaft toward a whirl extent, wherein the whirl extent is a line that passes through a center axis and is coplanar with the center axis.

2. The RAT of claim 1 , wherein the whirl reduction system includes damper connected to the third bearing and the housing.

3. The RAT of claim 1 , wherein the whirl reduction system includes damper connected to the third bearing and the housing with the spring.

4. The RAT of claim 1 , wherein the third bearing is aft of both of the first bearing and the second bearing.

5. The RAT of claim 4 , wherein a center of gravity of the RAT is forward of both of the first bearing and the second bearing.

6. The RAT of claim 1 , wherein the spring force includes a sufficient spring force to maintain a whirl extent under all loading conditions in flight.

7. An aircraft, comprising:

a ram air turbine (RAT) comprising:

a housing;

a turbine shaft configured to connect to one or more turbine blades and be turned by the one or more blades, the turbine shaft disposed in the housing to rotate relative to the housing along a rotational axis;

a first bearing and a second bearing mounted between the turbine shaft and the housing to allow the turbine shaft to rotate relative to the housing; and

a whirl reduction system configured to dampen or eliminate whirl around the rotational axis, wherein the whirl reduction system includes:

a third bearing between the housing the turbine shaft, and

a spring connected to the third bearing and to the housing to provide a spring force to the turbine shaft to bias the turbine shaft toward a whirl extent, wherein the whirl extent is a line that passes through a center axis and is coplanar with the center axis.

8. The aircraft of claim 7 , wherein the whirl reduction system includes damper connected to the third bearing and the housing.

9. The aircraft of claim 7 , wherein the whirl reduction system includes damper connected to the third bearing and the housing with the spring.

10. The aircraft of claim 7 , wherein the third bearing is aft of both of the first bearing and the second bearing.

11. The aircraft of claim 10 , wherein a center of gravity of the RAT is forward of both of the first bearing and the second bearing.

12. The aircraft of claim 7 , wherein the spring force includes a sufficient spring force to maintain a whirl extent under all loading conditions in flight.

13. A method for reducing whirl of a ram air turbine (RAT), comprising:

providing a spring force and/or damping between a turbine shaft and housing to dampen and/or eliminate whirl of the RAT, wherein providing a spring force includes providing a sufficient spring force to maintain a whirl extent under all loading conditions in flight.

14. The method of claim 13 , wherein providing a spring force and/or damping includes providing both a spring force and damping.

15. The method of claim 14 , wherein damping the whirl includes reducing a whirl extent.

16. The method of claim 15 , wherein reducing a whirl extent includes changing a whirl orbit shape about a rotational axis.