Adjustable blade outer air seal apparatus

1. An adjustable blade outer air seal apparatus, comprising:

a case extending circumferentially around an axis;

a support ring non-rigidly mounted to the case on spring connections radially inwards of the case, whereby the support ring radially floats with respect to the case; and

at least one blade outer air seal segment that is radially adjustable relative to the support ring;

wherein the at least one blade outer air seal segment includes a lower body portion that has a leading end and a trailing end, circumferential sides, and a radially inner gas path surface and an opposed radially outer surface, with a shaft that extends radially outwards from the radially outer surface and through an unthreaded opening in the support ring structure such that a threaded end of the shaft projects from an outer surface of the support ring structure.

2. The adjustable blade outer air seal apparatus as recited in claim 1 , wherein the spring connections bias the support ring to a centered position with respect to the case.

3. The adjustable blade outer air seal apparatus as recited in claim 1 , wherein the shaft includes an internal cavity.

4. The adjustable blade outer air seal apparatus as recited in claim 1 , further comprising an actuation arm that engages the threaded end.

5. The adjustable blade outer air seal apparatus as recited in claim 4 , further comprising a clamp secured on the threaded end such that the actuation arm is secured between the clamp and the support ring structure.

6. The adjustable blade outer air seal apparatus as recited in claim 5 , further comprising a thrust plate between the actuation arm and the support ring structure.

7. The adjustable blade outer air seal apparatus as recited in claim 1 , further comprising a spacer mounted adjacent the support ring structure, the spacer being adjustable in radial size, the radial size controlling a radial position of the at least one blade outer air seal segment relative to the support ring.

8. The adjustable blade outer air seal apparatus as recited in claim 7 , wherein the spacer includes a variable number of stacked washers that define the radial size of the spacer.

9. The adjustable blade outer air seal apparatus as recited in claim 1 , wherein the at least one blade outer air seal segment and the support ring structure include an anti-rotation feature limiting rotation of the at least one blade outer air seal segment about a radial axis, the anti-rotation feature including a slot and a tab received in the slot, and the tab and the slot are located at a leading end or a trailing end of the at least one blade outer air seal segment.

10. A gas turbine engine comprising:

a compressor section, a combustor section, and a turbine section,

at least one of the compressor section and the turbine section including an adjustable blade outer air seal apparatus comprising a case structure extending circumferentially about an engine central axis, a support ring structure non-rigidly mounted on spring connections radially inwards of the case structure, whereby the support ring structure radially floats with respect to the case structure, and at least one blade outer air seal segment radially adjustably mounted relative to the support ring structure;

further comprising a spacer mounted adjacent the support ring structure, the spacer being adjustable in radial size, the radial size controlling a radial position of the at least one blade outer air seal segment relative to the support ring.

11. The gas turbine engine as recited in claim 10 , further comprising a fan and a gear assembly, the fan being rotatably coupled to the turbine section through the gear assembly.

12. The gas turbine engine as recited in claim 10 , wherein the spring connections bias the support ring to a centered position with respect to the case.

13. The gas turbine engine as recited in claim 10 , wherein the spacer includes a variable number of stacked washers that define the radial size of the spacer.

14. A method for adjusting position of a blade outer air seal, the method comprising:

setting a starting radial position of a blade outer air seal to obtain a desired starting clearance between the blade outer air seal and a rotatable blade, the setting including adjusting a radial size of an adjustable spacer; and

after the setting, in response to one or more flight conditions, using an actuation arm for fine adjustment control of the radial position of the blade outer air seal; wherein:

the blade outer air seal is in a blade outer air seal apparatus having a case structure extending circumferentially about an engine central axis, a support ring structure non-rigidly mounted on spring connections radially inwards of the case structure, whereby the support ring structure radially floats with respect to the case structure, and the blade outer air seal segment is radially adjustably mounted relative to the support ring structure.

15. The method as recited in claim 14 , wherein the fine adjustment control includes changing the radial position in an increment of approximately 0.001 inches.

16. The method as recited in claim 14 , wherein the adjustable spacer includes a variable number of stacked washers that define the radial size of the spacer, and the setting includes selecting the number of the stacked washers to use.