Blade outer air seal with spring centering

1. A blade outer air seal assembly comprising:

a seal arc segment defining first and second seal supports;

a carriage defining first and second support members, the first support member supporting the seal arc segment in a first ramped interface and the second support member supporting the seal arc segment in a second ramped interface such that the seal arc segment is circumferentially moveable with respect to the carriage; and

first and second opposed springs biasing the seal arc segment toward a circumferential default position, the carriage including first and second deflection limiters and third and fourth deflection limiters, the first and second deflection limiters adjacent, respectively, the first and second springs, the first and second deflection limiters limiting low-load elastic movement of the first and second springs, the third and fourth deflection limiters radially adjacent, respectively, the first and second deflection limiters, the third and fourth deflection limiters limiting high-load elastic movement of the first and second springs.

2. The seal assembly as recited in claim 1 , wherein the first and second opposed springs are leaf springs.

3. The seal assembly as recited in claim 1 , wherein the first and second opposed springs bias the seal arc segment at, respectively, the first and second seal supports.

4. The seal assembly as recited in claim 3 , further comprising at least one shim between the seal arc segment and the first and second springs such that the first and second springs bias the seal arc segment through the at least one shim.

5. The seal assembly as recited in claim 1 , wherein the first spring biases the seal arc segment in a first circumferential direction and the second spring biases the seal arc segment in a second, opposite circumferential direction.

6. The seal assembly as recited in claim 1 , further comprising a third spring biasing the seal arc segment in a radial direction.

7. The seal assembly as recited in claim 6 , wherein the third spring is a leaf spring.

8. The seal assembly as recited in claim 1 , wherein each of the first and second deflection limiters comprises a protrusion with a curved bearing surface.

9. The seal assembly as recited in claim 1 , wherein the first and second springs each provide non-linear spring force.

10. A gas turbine engine comprising:

a rotor section including a rotor having a plurality of blades and at least one annular seal assembly circumscribing the rotor, the annular seal assembly comprising:

at least one seal arc segment defining first and second seal supports;

at least one carriage defining first and second support members, the first support member supporting the at least one seal arc segment in a first ramped interface and the second support member supporting the at least one seal arc segment in a second ramped interface such that the at least one seal arc segment is circumferentially moveable with respect to the at least one carriage; and

first and second opposed springs biasing the at least one seal arc segment toward a circumferential default position, the at least one carriage including first and second deflection limiters and third and fourth deflection limiters, the first and second deflection limiters adjacent, respectively, the first and second springs, the first and second deflection limiters limiting low-load elastic movement of the first and second springs, the third and fourth deflection limiters radially adjacent, respectively, the first and second deflection limiters, the third and fourth deflection limiters limiting high-load elastic movement of the first and second springs.

11. The gas turbine engine as recited in claim 10 , wherein the first and second opposed springs bias the seal arc segment at, respectively, the first and second seal supports.

12. The gas turbine engine as recited in claim 10 , wherein the first spring biases the seal arc segment in a first circumferential direction and the second spring biases the seal arc segment in a second, opposite circumferential direction.

13. The gas turbine engine as recited in claim 10 , further comprising a third spring biasing the seal arc segment in a radial direction.

14. The gas turbine engine as recited in claim 10 , wherein the first and second springs each provide non-linear spring force.

15. A method for maintaining positioning in a blade outer air seal assembly, the method comprising:

mounting a seal arc segment in a carriage on first and second ramped interfaces such that the seal arc segment is circumferentially moveable with respect to the carriage;

using first and second opposed springs to bias the seal arc segment toward a circumferential default position;

using first and second deflection limiters of the carriage that are adjacent, respectively, the first and second springs, to limit low-load elastic movement of the first and second springs; and

using third and fourth deflection limiters of the carriage that are radially adjacent, respectively, the first and second deflection limiters, to limit high-load elastic movement of the first and second springs.

16. The method as recited in claim 15 , wherein the first and second opposed springs bias the seal arc segment at, respectively, first and second seal supports of the seal arc segment.