FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesHard
A mechanic needs to detect a small surface crack in a nonferrous aluminum wing skin without removing paint or disassembling the structure. Which inspection method uses induced electrical currents to detect this type of flaw?
- AMagnetic particle inspection
- BRadiographic inspection
- CCoin tap test
- DEddy current inspection
Show answer & explanationAnswer & explanation
Correct answer: D. Eddy current inspection
Eddy current inspection induces alternating electrical currents into a conductive material and detects disruptions caused by surface or near-surface cracks; it works well on nonferrous conductive metals like aluminum and can often be performed through thin paint coatings.
Why the other options are wrong
- A. Magnetic particle inspection only works on ferromagnetic materials and aluminum is not magnetic.
- B. Radiographic inspection detects internal flaws using radiation but is less practical for quick surface crack checks and requires more safety precautions.
- C. Coin tap testing is used for detecting disbonds in composite/honeycomb structures, not metal cracks.
Eddy Current Inspection
A nondestructive testing method that induces alternating currents into a conductive material to detect surface and near-surface cracks, corrosion, or conductivity changes.
- Works only on electrically conductive materials
- Detects surface and near-surface flaws in metals
- Effective on nonferrous metals like aluminum
- Can often be performed without removing paint coatings
Memory trick: "Eddy currents swirl and stall at every crack."