Airframe Mechanic Certification Sheet Metal Structural Repairs 2 — Questions and Answers
Question 1: When performing a sheet metal repair, the minimum edge distance for a rivet from the edge of the sheet is typically:
- 1.5 times the rivet diameter (Correct answer)
- 2 times the rivet diameter
- 2.5 times the rivet diameter
- 3 times the rivet diameter
Correct answer: 1.5 times the rivet diameter
Minimum edge distance is 1.5 times the rivet diameter to prevent sheet splitting or edge tearout.
Question 2: Which type of corrosion appears as a white or gray powdery deposit on aluminum aircraft skin?
- Intergranular corrosion
- Galvanic corrosion
- Surface oxidation (white corrosion) (Correct answer)
- Stress corrosion cracking
Correct answer: Surface oxidation (white corrosion)
White or gray powdery deposits on aluminum are characteristic of surface oxidation, the most common and easily treated form of aluminum corrosion.
Question 3: A 'stop-drill' is used in sheet metal repair to:
- Create holes for new rivets
- Halt crack propagation by removing the stress concentration at the crack tip (Correct answer)
- Remove old rivets from damaged panels
- Align repair patches during installation
Correct answer: Halt crack propagation by removing the stress concentration at the crack tip
Stop-drilling places a hole at the end of a crack to redistribute stress and prevent the crack from continuing to grow.
Question 4: What is the purpose of using a dimpling operation in sheet metal work?
- To increase sheet thickness at rivet locations
- To create a countersunk recess in thin sheets that cannot be machine countersunk (Correct answer)
- To mark drill locations before punching
- To test material hardness before riveting
Correct answer: To create a countersunk recess in thin sheets that cannot be machine countersunk
Dimpling forms a countersunk recess in sheet metal that is too thin to machine countersink, allowing flush rivet installation.
Question 5: When sizing a rivet for a sheet metal repair, the correct rivet diameter should be:
- Equal to the total thickness of the sheets being joined
- 3 times the thickness of the thickest sheet (Correct answer)
- 3 times the diameter of the drill bit used
- Equal to the grip length of the material
Correct answer: 3 times the thickness of the thickest sheet
Rivet diameter should be approximately 3 times the thickness of the thickest sheet being joined for optimal strength.
Question 6: Which repair method is used when the damage to an aircraft skin panel is too extensive for a patch but the surrounding structure is still sound?
- Flush patch repair
- Insert repair
- Scab patch repair
- Section replacement (Correct answer)
Correct answer: Section replacement
Section replacement removes the entire damaged section and replaces it with new material when damage is too extensive for patching.
Question 7: What document must be consulted before performing any structural repair on a certificated aircraft?
- The aircraft flight manual (AFM)
- The aircraft's structural repair manual (SRM) or AC 43.13-1B (Correct answer)
- The manufacturer's parts catalog
- The avionics installation guide
Correct answer: The aircraft's structural repair manual (SRM) or AC 43.13-1B
The Structural Repair Manual (SRM) or AC 43.13-1B must be consulted to ensure all repairs meet approved data and airworthiness standards.
Airframe Mechanic Certification Sheet Metal Structural Repairs 2
When performing a sheet metal repair, the minimum edge distance for a rivet from the edge of the sheet is typically: