A&P - Aircraft and Powerplant Sheet Metal Structural Repair Questions and Answers

Question 1

When performing a sheet metal repair on an aircraft, what is the generally accepted minimum edge distance for a single row of protruding head rivets?

Accepted Answer

Two times the rivet shank diameter

Answer

According to FAA Advisory Circular (AC) 43.13-1B, the minimum edge distance, measured from the center of the rivet hole to the edge of the sheet, should be no less than two times the diameter of the rivet shank for a single row. This ensures sufficient material is present to prevent the rivet from tearing out under load.

Question 2

A technician discovers a 1.5-inch long crack in a non-structural aluminum alloy skin panel. Which of the following is the correct initial step to repair the crack?

Accepted Answer

Stop-drill the ends of the crack.

Answer

The proper procedure to prevent a crack from propagating further is to stop-drill each end of the crack. This involves drilling a small hole at the very tip of the crack, which distributes the stress concentration over a larger area, effectively halting its growth until a permanent repair can be made.

Question 3

In a sheet metal lap joint repair, the rivet pitch (the distance between the centers of adjacent rivets in the same row) should generally be no less than:

Accepted Answer

Three times the rivet diameter.

Answer

To ensure the strength of the joint and prevent the sheet metal from buckling or failing between fasteners, the standard minimum rivet pitch is three times the diameter of the rivet shank. Spacing them closer could weaken the material between the rivets.

Question 4

When fabricating a replacement part that requires a 90-degree bend, the term 'bend allowance' refers to:

Accepted Answer

The length of the curved portion of the metal within the bend.

Answer

Bend allowance is the specific length of the material in the curved area of a bend. It's calculated to ensure the final dimensions of the formed part are correct, as the material on the outside of the bend stretches and the inside compresses.

Question 5

A repair is being made to a section of 0.040-inch 2024-T3 aluminum skin using a doubler patch of the same material and thickness. According to common practice, what is the most appropriate solid shank rivet diameter to use for this repair?

Accepted Answer

1/8 inch (0.125")

Answer

A general rule of thumb for selecting rivet diameter is to use a rivet with a diameter that is at least three times the thickness of the thickest sheet being joined. In this case, 3 x 0.040" = 0.120". The closest standard rivet size that is equal to or greater than this value is 1/8 inch (0.125").

A&P - Aircraft and Powerplant Certification Practice Test

A&P - Aircraft and Powerplant Certification Practice Test

A&P - Aircraft and Powerplant Sheet Metal Structural Repair Questions and Answers