Double seal element seal assembly for aircraft system

1 . A system for an aircraft, comprising:

a first rotating structure rotatable about an axis;

a second rotating structure rotatable about the axis, the second rotating structure secured to the first rotating structure;

a stationary structure axially overlapping the first rotating structure and the second rotating structure;

a first seal element fixed to the stationary structure and sealingly engaging the first rotating structure; and

a second seal element fixed to the stationary structure and sealingly engaging the first rotating structure, the second seal element axially next to the first seal element;

wherein a cavity is formed by and extends axially between the first seal element and the second seal element, the cavity is formed by and radially adjacent the first rotating structure, and the stationary structure comprises a drain passage fluidly coupled to the cavity,

wherein the second rotating structure is secured to the first rotating structure at an interface between the first rotating structure and the second rotating structure, and

wherein the first seal element or the second seal element is axially aligned with the interface between the first rotating structure and the second rotating structure.

2 . The system of claim 1 , wherein

the second rotating structure projects into a bore of the first rotating structure; and

the stationary structure axially overlaps the interface between the first rotating structure and the second rotating structure.

3 . The system of claim 2 , wherein

the stationary structure circumscribes the interface between the first rotating structure and the second rotating structure; and

the first seal element and the second seal element each circumscribe the first rotating structure.

4 . The system of claim 1 , wherein

the first seal element is axially between and fluidly separates the cavity and a first volume; and

the second seal element is axially between and fluidly separates the cavity and a second volume, and the second volume is fluidly discrete from the first volume.

5 . The system of claim 4 , further comprising:

a first lubrication system servicing one or more components within the first volume; and

a second lubrication system servicing one or more components within the second volume.

6 . The system of claim 1 , wherein at least one of

the first seal element radially engages the first rotating structure; or

the second seal element radially engages the first rotating structure.

7 . The system of claim 1 , wherein

the first rotating structure comprises a seal land surface; and

the first seal element and the second seal element each contact the seal land surface.

8 . The system of claim 1 , wherein

the first rotating structure comprises a first seal land surface and a second seal land surface;

the first seal element sealingly engages the first seal land surface; and

the second seal element sealingly engages the second seal land surface.

9 . The system of claim 1 , wherein at least one of

the first seal element comprises a first lip seal; and

the second seal element comprises a second lip seal.

10 . The system of claim 1 , wherein at least one of

the first seal element comprises a first polymeric material; and

the second seal element comprises a second polymeric material.

11 . The system of claim 1 , wherein at least one of

the first seal element comprises a first carbon face seal; and

the second seal element comprises a second carbon face seal.

12 . The system of claim 1 , further comprising:

a seal carrier removably mounted to the stationary structure;

the first seal element and the second seal element each attached to the seal carrier.

13 . The system of claim 1 , wherein the first seal element and the second seal element are each attached directly to the stationary structure.

14 . The system of claim 1 , further comprising a bearing rotatably mounting the first rotating structure to the stationary structure, the bearing axially next to the second seal element.

15 . The system of claim 1 , further comprising:

an aircraft powertrain including a powerplant, a power transmission, a clutch system and a bladed rotor, the power transmission operatively coupling the powerplant to the clutch system, the clutch system operatively coupling the power transmission to the bladed rotor, and the powerplant configured to drive rotation of the bladed rotor through the power transmission and the clutch system when the clutch system is engaged;

the power transmission comprising the first rotating structure; and

the clutch system comprising the second rotating structure.

16 . The system of claim 1 , further comprising:

a container configured to collect fluid drained from the cavity through the drain passage.

17 . A system for an aircraft, comprising:

a power transmission comprising a first rotating structure that is rotatable about an axis;

a clutch system comprising a second rotating structure that is rotatable about the axis, the second rotating structure coupled to and rotatable with the first rotating structure;

a stationary structure circumscribing the first rotating structure;

a first seal element fixed to the stationary structure and sealingly engaging the first rotating structure; and

a second seal element fixed to the stationary structure and sealingly engaging the first rotating structure, the second seal element axially adjacent the first seal element,

wherein the second rotating structure is coupled to the first rotating structure at an interface between the first rotating structure and the second rotating structure, and

wherein the first seal element or the second seal element is axially aligned with the interface between the first rotating structure and the second rotating structure.