FAA Aviation Mechanic Airframe (AMA)Airframe InspectionMedium
A technician is inspecting the area around rivet holes on an aluminum wing skin for subsurface fatigue cracks without disassembling the structure. Which NDT method is most appropriate for this application?
- AVisual inspection with a 10x loupe
- BDye penetrant inspection
- CMagnetic particle inspection
- DEddy current inspection
Show answer & explanationAnswer & explanation
Correct answer: D. Eddy current inspection
Eddy current inspection is well suited for detecting surface and subsurface cracks around fastener holes in conductive nonferrous materials like aluminum without disassembly.
Why the other options are wrong
- A. A loupe only reveals visible surface conditions, not hidden subsurface cracks
- B. Dye penetrant only detects surface-breaking cracks, not subsurface ones
- C. Magnetic particle only works on ferromagnetic materials, not aluminum
Eddy Current Inspection
An NDT method that induces electrical eddy currents in a conductive material; disruptions from cracks or corrosion change the current's magnetic field response.
- Effective on both ferrous and nonferrous conductive metals
- Commonly used to inspect around fastener holes for fatigue cracks
- Can detect surface and shallow subsurface flaws without disassembly
Memory trick: Eddy currents swirl and stumble when they hit a hidden crack near a rivet