Surface Preparation Of Metallic Structure To Achieve Electrical Bonding For The Rotables On Fighter Aircraft

Abstract

An aircraft consist no. of rotables of various systems which are electrically connected. It is required to establish sufficient electrical continuity between the body of the rotable and its mounted structure to avoid mal-functioning of rotables from EMI/EMC effects and protect them from lightening. The metallic structures are usually anodic coated and are painted with epoxy primer which are resistant to the electric current. This invention is intended for the surface preparation required on aircraft metallic structure components to achieve electrical bonding value of less than 2.5milliohms for rotables mounted on the component.

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DESCRIPTION

TECHNICAL FIELD

The invention describes a process used to achieve required electrical bonding value (less than 2.5milliohm) between the rotables and its mounting structure on an aircraft.

BACKGROUND OF INVENTION

All electrically connected rotables are to be electrically bonded to the aircraft structure to protect the rotables from EMI/EMC effect, electrical charges developed on the rotable and protection against lightening. Structure components of the aircraft are anodized and are painted with epoxy primer to protect from corrosion. Anodic coating and epoxy primer are resistant in nature to electrical current and hence direct mounting of the rotable on the structure component will not give required bonding value. A procedure is required to prepare the surface of mating area of the structure component to get electrical bonding for the rotable without compromise on the protection from corrosion.

SUMMARY OF INVENTION

Structure component has to be prepared by removing existing anodic coating locally and protecting the same with a coat which is anti-rusting and electrical conductive in nature.

PROCESS DETAIL DESCRIPTION

i. Clean to bare metal the structure covered by the foot of the rotable. The cleaned
areas being such that, after assembly, they extend 1 to 2mm around the contacting surfaces. The recommended method of removal is as follows: a. Mask around the area to be treated to contain the effect of abrasives. Remove the surface treatment finish from the area which is forming the bond using 320 grade or finer abrasive paper. Remove all dust with a clean paper tissue.

b. Remove all surface blemishes by cleaning with Aluminium wool or Polyamide
abrasive pads.

c. Remove all dust by cleaning in accordance with HPS101.

ii. Apply one coat of Alochrome-1200.

iii. Fix the rotable with fasteners as per the engineering drawing.

iv. Over seal the above extended 1 to 2mm area with barrier coat (PR1005).

DRAWINGS:

Fig-1: Rotable mounted structure component

CLAIMS

We claim the process of surface preparation of metallic structure (anodic coated aluminum alloys) to achieve required electrical bonding (less than 2.5milliohm) for rotable on fighter aircraft.

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