Sheet Metal Structural Repair Flashcards

Which repair method restores the greatest percentage of original strength in a damaged aircraft skin panel?

Answer: Flush patch repair

A flush patch (insert patch) restores close to 100% of original strength because it maintains the original skin thickness and aerodynamic surface.

What is the correct sequence for laying out rivet holes in a sheet metal repair pattern?

Answer: Mark rivet locations, drill patch, cleco, drill structure

Rivet holes are laid out on the patch first, drilled, then the patch is clecoed to the structure and used as a template to drill the structure.

Which type of corrosion is most likely to occur between aluminum aircraft skin and a steel fastener?

Answer: Galvanic corrosion

Galvanic corrosion occurs when dissimilar metals (aluminum and steel) are in electrical contact in the presence of an electrolyte.

What is the purpose of using a cleco fastener during a sheet metal repair?

Answer: To temporarily hold parts in alignment while drilling and riveting

Clecos are temporary spring-loaded fasteners used to hold sheets in position while remaining holes are drilled and rivets installed.

When cutting a repair patch from aluminum sheet stock, the corners of rectangular patches should be:

Answer: Clipped or radiused to reduce stress concentration

Square corners on repair patches create stress concentrations that can initiate cracks, so corners must be radiused or clipped.

What does the 'T' designation in an aluminum alloy temper (e.g., 2024-T3) indicate?

Answer: The alloy has been thermally treated

The 'T' temper designation indicates the alloy has been thermally treated (heat treated) to improve mechanical properties.

When using a countersink tool to prepare holes for flush rivets, what angle is used for standard 100-degree countersunk (AN426) rivets?

Answer: 100 degrees

AN426 (MS20426) rivets have a 100-degree head angle, so countersunk holes must also be cut to 100 degrees to achieve a flush fit.