Anti-spark structure, in particular for aircraft

Details Anti-spark structure, in particular for aircraft Anti-spark structure, in particular for aircraft

1995-11-30

1998-01-20

Grant, William

Aeronautics and astronautics

Miscellaneous

244132, 361218, B64D 4502

Patent

active

057093563

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to anti-spark structures, in particular for aircraft.


BACKGROUND OF THE INVENTION

Already known are structures including: inner face and which two elements are located such that the inner face of the first of said elements is at least partially superimposed on the outer face of the second of said elements, the superimposed parts of said elements including pairs or opposing holes; said opposing holes such that its head becomes housed in a countersink provided in the outer face of said first element; the inner face of said second element in order to press the countersunk head of the corresponding screw into said countersink.
When such a structure is subjected to the action of lightning, the discharge current is propagated via the screws toward said first and second elements and toward said nuts.
Owing to the generally high density of said discharge current and to the high resistance to current at the interface between on the one hand said screws and on the other hand said first and second elements, significant heating takes place at said interface by the Joule effect. This heating may at least locally melt the composite material of said first and second elements and thus create sublimation gases at said interface.
Such gases can give rise to overpressures which may destroy said structure.
Furthermore, the significant heating and significant sparking which are generated then may also be extremely damaging to the structure, especially if the latter forms part of a fuel tank, posing a risk of fuel catching fire.
It will be noted that the physical phenomena described above are even more substantial between the nut and the second element. This is because some of the discharge current coming from the screw arrives in the nut, without appreciable heating at the interface between the screw and the nut. There is no appreciable heating because the resistance at the interface is low, and is directed into the second element transversely thereto. This current directed transversely encounters high resistance especially if the second element consists of a carbon-carbon structure for which current flows much more easily longitudinally than transversely.
In order to remove the gases formed at the interface between the screw and the first and second elements, document GB-2 226 801 proposes two different solutions. According to a first solution, provision is made to replace the nut with a female element exhibiting a complicated shape and a substantial bulk, and including at least one storage chamber which is open toward the second element. The storage chamber is intended to recover and to store the gases formed at the interface. Even though, by means of such an orientation of the opening allowing access to the chamber, the female element is quite able to recover the gases formed, this solution is not really very attractive from the industrial point of view because the female element is much too complex for the envisaged use, regardless of the embodiment proposed.
According to a second solution of the GB-2 226 801 document, provision is made to form, in the screw, passages allowing certain regions of the interface to be made to communicate with the outside of the structure, in order to remove the gases formed at the interface directly to the outside. However, since such a solution can be envisaged only locally, it is impossible to recover all the gases formed at the interface. This is indeed what the aforementioned document explicitly confirms, because in such cases storage chambers are provided in the nut for the gases which could not be removed by the passages provided in the screw. This second solution is also, therefore, not satisfactory.
The object of the present invention is to overcome these drawbacks and to allow, using only standard, barely modified nuts, the structure to be made resistant to bolts of lightning. It is also an object of the invention to find a solution to the problem posed by the gases which are inevitably formed at the interface between the screw

REFERENCES:
patent: 2787185 (1957-04-01), Rea et al.
patent: 3755713 (1973-08-01), Paszkowski
patent: 3989984 (1976-11-01), Amason et al.
patent: 4556591 (1985-12-01), Bannink, Jr.
patent: 4755904 (1988-07-01), Brick
patent: 4839771 (1989-06-01), Covey
patent: 4891732 (1990-01-01), Jones
patent: 4905931 (1990-03-01), Covey
patent: 5175665 (1992-12-01), Pegg
patent: 5314144 (1994-05-01), Porter, Jr. et al.
patent: 5461534 (1995-10-01), Gondot et al.

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