FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesMedium
A technician suspects internal porosity inside a cast aluminum engine housing that shows no surface indications. Which nondestructive inspection method is best suited to detect this defect?
- ALiquid penetrant inspection
- BMagnetic particle inspection
- CRadiographic (X-ray) inspection
- DCoin tap test
Show answer & explanationAnswer & explanation
Correct answer: C. Radiographic (X-ray) inspection
Radiographic (X-ray) inspection uses penetrating radiation to reveal internal defects such as porosity, voids, and inclusions inside castings that are not visible or accessible from the surface.
Why the other options are wrong
- A. Liquid penetrant inspection only detects defects open to the surface, not internal porosity.
- B. Magnetic particle inspection only detects surface and near-surface flaws in ferromagnetic materials, and aluminum is not magnetic.
- D. Coin tap testing detects disbonds in laminated/honeycomb composite structures, not internal metal casting defects.
Radiographic (X-ray) Inspection
A nondestructive testing method using penetrating radiation to reveal internal flaws such as porosity, cracks, or inclusions inside metal parts.
- Detects internal/subsurface defects invisible to other methods
- Commonly used on castings and welds
- Requires radiation safety precautions and shielding
- Produces a film or digital image showing density variations
Memory trick: "X-rays see through metal like a flashlight through fog."