Turbine engines with variable area nozzle

1. A turbine engine, comprising:

an engine core;

an inner cowl radially surrounding the engine core;

an outer cowl radially surrounding the inner cowl and spaced from the inner cowl to form an annular passage, between the inner cowl and the outer cowl that defines a nozzle;

at least one control surface having a first end hingedly mounted to the inner cowl and a second end, opposite the first end, the at least one control surface movable between a retracted position, where the nozzle has a first cross-sectional area, and an extended position where the second end moves away from the inner cowl and the nozzle has a second cross-sectional area that is less than the first cross-sectional area, the first end forward of the second end;

an actuator operably coupled to the at least one control surface and configured to move the at least one control surface to control the cross-sectional area of the nozzle; and

a seal coupling the second end to the inner cowl, where the seal is elastic and is sized to stretch when the at least one control surface is moved from the retracted position to the extended position.

2. The turbine engine of claim 1 wherein the outer cowl translates axially relative to the engine core.

3. The turbine engine of claim 1 wherein the first cross-sectional area is sized for take-off operation and the second cross-sectional area is sized for cruise operation.

4. The turbine engine of claim 1 wherein the second cross-sectional area is up to ten percent less than the first cross-sectional area.

5. The turbine engine of claim 1 wherein the at least one control surface comprises multiple control surfaces circumferentially spaced about the engine core.

6. The turbine engine of claim 1 wherein the actuator comprises an inflatable airbag and wherein inflation of the inflatable airbag moves the at least one control surface from the retracted position to the extended position.

7. The turbine engine of claim 1 wherein an elastic force of the seal biases the at least one control surface from the extended position to the retracted position.

8. The turbine engine of claim 7 wherein the actuator comprises an inflatable airbag, which when inflated hingedly moves the at least one control surface from the retracted position to the extend position.

9. The turbine engine of claim 8 wherein the at least one control surface provides access from the inner cowl to the engine core.

10. The turbine engine of claim 1 wherein the at least one control surface is movable to at least one intermediate position, between the retracted position and the extended position.

11. The turbine engine of claim 10 wherein the at least one control surface is moveable to multiple intermediate positions and the actuator is configured to continuously vary the position of the at least one control surface.

12. A turbine engine, comprising:

an engine core;

an inner cowl radially surrounding the engine core and having a set of cowl doors, movable from a closed position to an opened position, spaced circumferentially about the engine core, wherein at least one cowl door in the set of cowl doors includes a first end that is hingedly mounted to the inner cowl and a second end, opposite the first end, that moves away from the inner cowl when the at least one cowl door moves from the closed position to the opened position;

an outer cowl radially surrounding the inner cowl and spaced from the inner cowl to form an annular passage, between the inner cowl and the outer cowl, that defines a nozzle having a cross-sectional area;

an elastic seal, sized to stretch when the at least one cowl door is moved from the closed position to the opened position, coupling the second end to the inner cowl; and

at least one inflatable airbag located between a subset of the set of cowl doors and the engine core that when inflated moves the subset of the set of cowl doors towards the opened position, wherein in the opened position the subset of the set of cowl doors reduce the cross-sectional area of the nozzle.

13. The turbine engine of claim 12 wherein in the opened position the subset of the set of cowl doors reduce the cross-sectional area of the nozzle by up to ten percent.

14. The turbine engine of claim 12 wherein the at least one inflatable airbag is configured to move the subset of the set of cowl doors to multiple intermediate positions.