Aircraft Rivet Nut As Opposed to Aerospace Composite Structures

Repairs to riveted or rivet nut truss type structures should be made employing some general principles. Methods for repair of important members ought to be particularly approved by a representative of the Federal Aviation Administration.

Aluminium alloy aerospace rivet nut

Extensive repairs to damaged stressed skin on monocoque kinds of aluminium alloy structures should preferably be made in accordance with specific recommendations of the producer of the aircraft. In many cases, repair parts, joints, or reinforcements can be designed, and proof of adequate strength shown, without the calculation of the design loads and stresses, by properly considering the material and dimensions of the original parts as well as the rivet nut. Examples illustrating the principles of this method as applied to typical repairs may be found in textbooks on metal structures. A significant point to bear in mind in making repairs on monocoque structures is that a repaired part must be as strong as the original with respect to all kinds of loads as well as general rigidity.

Disassembly Prior to Repairing.

If the parts to be removed are essential to the rigidity of complete aircraft structures, support the remaining structure prior to disassembly in such a manner as to prevent distortion and permanent damage to the remainder of the structure. When rivet nuts are to be removed, weaken the rivet head by drilling. Use a drill of the same size as the rivet. Drilling must be exact center and to the base of the head only. After drilling, break off the head with a pin punch as well as carefully drive out the shank. Removal of rivet heads with a cold chisel and hammer is not recommended simply because skin damage and distorted rivet holes will probably result. Care must also be taken whenever rivet nut must be removed for disassembly or removal of stress plates, access plates, fillets, and so on., to avoid damage to adjoining structure. When properly used, impact wrenches can be effective tools for removal of rivet nut; however, damage to adjoining structure may result from excessive vertical loads being applied through the screw axis. Excessive loads are generally related to improperly adjusted impact tools or attempting to remove screws that have seized from corrosion. Remove seized rivet nut by drilling and use of a screw extractor. Structural cracks may appear in the doubler that runs parallel to the line of anchor or plate nuts installed for securing access doors or plates. Inspect rivet joints adjacent to damaged structure for partial failure (slippage) by removing one or more rivets to see if holes are elongated or the rivet nuts have started to shear.

Rivet nut for replacement aircraft structures.

In selecting the rivet nuts, it's usually satisfactory to use 2024 in place of 2017 since the former is stronger. Therefore, it will not be permissible to replace 2024 by 2017 unless the deficiency in strength of the latter material is compensated by an increase in material thickness, or the structural strength is substantiated by tests or analysis. Information on the comparative strength properties of these alloys, as well as 2014, 6061, 7075, and so on., is available. The choice of temper depends upon the severity of the subsequent forming operations. Parts having single curvature and straight bend lines with a large bend radius may be advantageously formed from heat-treated material, while a part, like a fuselage frame, would have to be formed from soft, annealed sheet and heat-treated after forming. Ensure sheet metal parts which are to be left unpainted are made of clad (aluminum coated material. Make sure all sheet material and finished parts are free from cracks, scratches ( kinks, tool marks, corrosion pits, and other defects which may be factors in subsequent failure.