Which method of magnetic particle inspection is used most often to inspect aircraft parts for invisible cracks and other defects?

• A. Residual
• B. Inductance
• C. Continuous
• D. Degauss

Answer: (C)

Magnetic particle inspection detects flaws by magnetizing a part and looking for leakage fields at discontinuities. The continuous method keeps the magnetic field active while the particles are applied and while the part is inspected. This allows indications to form immediately at surface and near-surface cracks as you scan or move the part, making it quick and reliable for detecting invisible or tightly closed cracks.

In aircraft maintenance, parts often pass through inspection stations or are scanned over extended surfaces, so having a magnetizing field always present during particle application lets inspectors spot cracks promptly and over large areas. Fluorescent particles with UV lighting further enhance visibility of even tiny indications, which is why this approach is used most often.

Other methods may be used in more limited situations, but they don’t provide the same combination of speed, continuous observation, and sensitivity that the continuous method offers for aircraft components.