Fan blade containment system for gas turbine engine

1. A fan blade containment system for surrounding a fan comprising a plurality of fan blades in a gas turbine engine for an aircraft, the fan blade containment system comprising:

a fan case arranged to surround the fan;

a debris retainer extending inwardly from the fan case and arranged to prevent forward debris release should all or part of one of the plurality of fan blades become detached from the fan when the fan blade containment system is installed in the gas turbine engine; and

a front panel:

mounted on the fan case and located forward of the fan and rearward of the debris retainer when the fan blade containment system is installed in the gas turbine engine,

arranged to move or break if struck by the detached all or part of one of the plurality of fan blades so as to facilitate the detached all or part of one of the plurality of fan blades engaging the debris retainer when the fan blade containment system is installed in the gas turbine engine, and

comprising a core sandwiched between a backing sheet and a face sheet, a thickness of the face sheet selected to trigger failure of the front panel if a load on the front panel meets or exceeds a first set threshold.

2. The fan blade containment system of claim 1 wherein the front panel is a front acoustic panel.

3. The fan blade containment system of claim 1 , wherein the front panel has a forward edge and a rearward edge and is detachably connected to the fan case at its forward edge such that a forward region of the front panel can move toward the fan case if struck when the fan blade containment system is installed in the gas turbine engine.

4. The fan blade containment system of claim 3 , wherein the front panel is arranged to be detachably connected to the fan case by a frangible connector, the frangible connector being arranged to break in response to pressure applied by the detached all or part of one of the plurality of fan blades when the fan blade containment system is installed in the gas turbine engine.

5. The fan blade containment system of claim 1 , wherein the front panel has a forward edge and a rearward edge and is cantilevered by connection to the fan case at its rearward edge such that a forward region of the front panel can move toward the fan case if struck when the fan blade containment system is installed in the gas turbine engine.

6. The fan blade containment system claim 1 , comprising a gap between a forward edge of the front panel and the debris retainer, the gap being arranged to expose the debris retainer to debris traveling forward on a surface of the front panel when the fan blade containment system is installed in the gas turbine engine.

7. The fan blade containment system of claim 1 , wherein the backing sheet is arranged to fail if the load on the front panel meets or exceeds a second set threshold.

8. The fan blade containment system of claim 7 , wherein the backing sheet comprises one or more holes arranged to trigger failure of the front panel if the load on the front panel meets or exceeds the second set threshold.

9. The fan blade containment system of claim 7 , wherein a thickness of the backing sheet is selected to trigger failure of the front panel if the load on the front panel meets or exceeds the second set threshold.

10. The fan blade containment system of claim 1 , wherein the face sheet comprises one or more holes arranged to trigger failure of the front panel if the load on the front panel meets or exceeds the first set threshold.

11. The fan blade containment system of claim 1 , wherein the face sheet comprises a wrinkle in the face sheet which is arranged to trigger failure of the front panel if the load on the front panel meets or exceeds the first set threshold.

12. The fan blade containment system of claim 1 , wherein the front panel is arranged to trigger shear failure of the core if the load on the front panel meets or exceeds a third set threshold.

13. The fan blade containment system of claim 1 , further comprising a gap or compressible region between a forward region of the front panel and the fan case, the gap or compressible region being arranged to facilitate movement of a forward region of the front panel toward the fan case if struck when the fan blade containment system is installed in the gas turbine engine.

14. The fan blade containment system of claim 1 , wherein the front panel is arranged to be penetrated by debris if struck when the fan blade containment system is installed in the gas turbine engine, if a load exerted by the debris meets or exceeds a third set threshold.

15. The fan blade containment system of claim 14 , wherein the backing sheet or the face sheet of the front panel comprises one or more joints and/or one or more holes arranged to facilitate shear of the face sheet if struck when the fan blade containment system is installed in the gas turbine engine.

16. The fan blade containment system of claim 1 , wherein the fan case is a composite fan case and further comprises a metallic insert mounted on the composite fan case, the metallic insert comprising the debris retainer and having the front panel at least partially mounted thereon.

17. A gas turbine engine for an aircraft comprising:

a fan comprising a plurality of fan blades; and

a fan blade containment system according to claim 1 surrounding the fan.