FAA Aviation Mechanic Airframe (AMA)Airframe StructuresMedium
A technician wants to inspect an unpainted aluminum wing skin for small surface cracks around rivet holes without disassembling the structure or removing paint. Which nondestructive inspection method is best suited for this task?
- ADye penetrant inspection
- BMagnetic particle inspection
- CUltrasonic thickness testing
- DEddy current inspection
Show answer & explanationAnswer & explanation
Correct answer: D. Eddy current inspection
Eddy current inspection is well suited for detecting surface and near-surface cracks in conductive materials such as aluminum, and it can often be performed through thin paint or coatings without requiring surface preparation like cleaning or stripping, unlike dye penetrant which requires bare, clean metal.
Why the other options are wrong
- A. Dye penetrant requires bare, clean metal and would require paint removal first.
- B. Magnetic particle inspection only works on ferromagnetic materials, not aluminum.
- C. Ultrasonic thickness testing measures material thickness/delamination, not primarily surface cracks around holes.
Eddy Current Inspection
A nondestructive inspection method using induced electrical currents to detect surface and near-surface flaws in conductive materials, often without removing paint.
- Works only on electrically conductive materials
- Can detect cracks around fastener holes without disassembly
- Sensitive to material conductivity changes, thickness, and flaws
Memory trick: 'Eddy Currents Swirl Through Paint' — no strip needed for surface cracks.