Sheet Metal Structural Repair Flashcards

A technician discovers a 0.75-inch crack propagating from a rivet hole on a non-pressurized fuselage skin panel. According to standard aviation maintenance practices, what is the first corrective action that must be taken?

Answer: Consult the aircraft's Structural Repair Manual (SRM).

Before any physical repair action is performed, the Structural Repair Manual (SRM) must be consulted. The SRM is the manufacturer's approved document that provides specific damage limits, inspection criteria, and detailed repair procedures. Attempting a repair, even a standard procedure like stop-drilling, without first consulting the SRM could result in an unapproved and unairworthy repair.

In sheet metal layout for riveting, what is the term for the distance measured from the center of a rivet to the nearest edge of the metal?

Answer: Edge distance

Edge distance is the critical measurement from the center of a rivet to the edge of the sheet. Maintaining the proper edge distance, typically two to four times the rivet shank diameter, is essential to prevent the rivet from tearing out the edge of the material under load. Rivet pitch is the distance between adjacent rivets in the same row.

A technician is performing a repair that specifies the use of a universal head rivet made from 2117-T4 aluminum alloy. What manufacturer's mark should the technician look for on the head of the correct rivet?

Answer: A small dimple

Solid shank rivets are marked on their heads to identify the material alloy. A rivet made from 2117-T4 aluminum alloy, designated by the letters 'AD' in its part number (e.g., AN470AD), is identified by a small dimple in the center of the head. A raised dot indicates a 2017 ('D') alloy, two raised dashes indicate a 2024 ('DD') alloy, and a plain head indicates 1100 ('A') aluminum.

A technician is fabricating a bracket from a sheet of 0.040-inch thick aluminum alloy. The plans call for a single 90-degree bend with an inside bend radius of 0.125 inches. What is the correct setback for this bend?

Answer: 0.165 inches

For a 90-degree bend, the setback is calculated using the formula: Setback (SB) = Bend Radius (BR) + Material Thickness (MT). In this case, SB = 0.125" (BR) + 0.040" (MT), which equals 0.165 inches. The setback value is used to determine the location of the bend tangent line on the flat layout.

When repairing damage to the skin of a pressurized aircraft fuselage, which type of patch is required to restore the necessary strength and maintain aerodynamic smoothness?

Answer: A flush patch.

A flush patch is required for repairing the skin of pressurized aircraft and in areas where aerodynamic smoothness is critical. This type of repair involves a filler plug of the same thickness as the skin, supported by an internal doubler plate that carries the structural loads. This ensures a smooth external surface and proper load transfer.

Which of the following tool combinations is used to properly install a solid shank rivet by forming the shop head?

Answer: A rivet gun and a bucking bar.

A solid shank rivet is installed using a pneumatic rivet gun to apply force to the manufactured head and a heavy steel bucking bar held against the shank end. The impact from the gun, resisted by the inertia of the bucking bar, causes the shank to deform and create the 'shop head,' which clamps the metal sheets together.