Spark containment cap

1. A joint comprising:

a structure;

an end of a fastener protruding from the structure; and

a unitary cap having an annular base terminating at a base rim and an annular mating feature on an external side of the annular base,

wherein the mating feature has an upper side and a lower side, and wherein the mating feature extends from an inboard end that meets the external side of the annular base to an outboard edge,

the annular base being at least substantially in abutment with the structure and the cap forming a sealed air cavity around the end of the fastener, the joint comprising a cured sealing material enclosing at least part of the mating feature to secure the cap to the structure, and

wherein the cured sealing material contacts the upper side, lower side and outboard edge of the mating feature.

2. An aircraft comprising the joint of claim 1 .

3. A sealing material distribution tool for injecting sealing material around an external side of a spark prevention cap, the tool comprising:

an annular passage,

a sealing material inlet to the annular passage and a sealing material outlet from the annular passage,

wherein the sealing material outlet has an annular configuration configured to distribute sealing material circumferentially about the external side of the spark prevention cap,

wherein the sealing material inlet is configured so that the sealing material flows circumferentially from the inlet along the annular passage, and

wherein the sealing material distribution tool is configured to be removed following application of the sealing material.

4. The tool of claim 3 , wherein the sealing material outlet comprises a plurality of outlet apertures.

5. The tool of claim 4 , wherein the diameter of at least one of the plurality of outlet apertures distal to the inlet is greater than the diameter of at least one of the plurality of outlet apertures proximal to the inlet.

6. The tool of claim 4 , wherein at least one of the plurality of outlet apertures is on at least one of an inner radial side of the annular passage and an underside of the annular passage.

7. The tool of claim 3 , wherein the annular pipe is resilient.

8. The joint of claim 1 , wherein the mating feature comprises a flange protruding from the external side of the annular base.

9. The joint of claim 8 , wherein the flange extends substantially parallel to the plane defined by the base rim from the juncture with the external side of the annular base to a free end of the flange.

10. The joint of claim 1 , wherein the mating feature is spaced from the base rim.

11. The joint of claim 1 , wherein the mating feature comprises at least one of a protrusion on the external side of the annular base and a recess in the external side of the annular base.

12. The joint of claim 11 , wherein the mating feature is one of a plurality of mating features.

13. The joint of claim 11 , wherein the at least one of the protrusion on the external side of the annular base and the recess in the external side of the annular base extends circumferentially.

14. The joint of claim 1 , wherein the unitary cap comprises an engaging feature configured to engage with the end of the fastener and locate the base rim against the surface of the structure.

15. A one-piece spark prevention cap for forming a sealed cavity around an end of a fastener protruding from a surface of a structure, the cap comprising:

a cap body with an annular base terminating at a base rim which surrounds an opening into a central cavity for receiving the end of the fastener;

the annular base having an external circumferential surface extending from the base rim, and an annular flange on the external circumferential surface configured to contact a sealant material applied externally to the cap; and,

wherein the flange has an upper side that extends substantially parallel to the plane defined by the base rim from the juncture with the external side of the annular base to a free end of the flange, and the flange has a lower side that extends substantially parallel to the plane defined by the base rim from the juncture with the external side of the annular base to a free end of the flange.

16. A one-piece spark prevention cap for forming a sealed cavity around an end of a fastener protruding from a surface of a structure, the cap comprising:

a cap body with an annular base terminating at a base rim which surrounds an opening into a central cavity for receiving the end of the fastener; and,

the annular base having an external circumferential surface extending from the base rim, and a recess in the external circumferential surface configured to contact a sealant material applied externally to the cap, wherein the recess comprises a circumferentially extending channel.

17. The cap of claim 16 , wherein the recess is one of a plurality of recesses.

18. A method of forming a sealed cavity around an end of a fastener protruding from a surface of a structure, the method comprising:

fitting a spark prevention cap over the end of the fastener;

the spark prevention cap comprising a cap body with an annular base terminating at a base rim which surrounds an opening into a central cavity for receiving the end of the fastener; and the method further comprising:

disposing a sealing material distribution tool for injecting sealing material around an external side of the spark prevention cap; and

injecting sealing material through the sealing material distribution tool around the juncture of the structure and the cap,

wherein the sealing material distribution tool comprises an annular passage and a sealing material inlet to the annular passage, wherein the sealing material flows circumferentially from the inlet along the annular passage and

wherein the sealing material distribution tool is removed following application of the seal material.

19. The method of claim 18 , wherein the sealing material distribution tool comprises an annular passage and a sealing material outlet from the annular passage with an annular configuration configured to distribute sealing material circumferentially about the spark prevention cap.