Disassembly, Inspection, Repair & Assembly
Defect recognition and visual inspection; non-destructive testing methods and their applications; repair schemes and limits; SB and AD compliance.
Inspection & NDT, summary notes
- Covers defect recognition, cleaning, non-destructive testing, repair schemes and limits, and compliance with service bulletins and airworthiness directives.
- Common defects: cracks, corrosion, wear, distortion, fretting, pitting, dents, scores and heat/overload damage. Visual inspection, aided by magnification and borescopes, is the first line.
- NDT, non-destructive testing, finds defects without damaging the part. DYE PENETRANT reveals surface-breaking flaws in any non-porous material (limit: surface-breaking only).
- MAGNETIC PARTICLE finds surface and slightly sub-surface cracks in FERROMAGNETIC materials only, it cannot be used on aluminium or austenitic stainless steel.
- EDDY CURRENT finds surface and near-surface cracks in conductive materials and works through thin coatings (limit: skilled interpretation, limited depth). ULTRASONIC finds internal and volumetric defects and measures thickness (limit: needs a couplant, access and skill).
- RADIOGRAPHY (X-ray) images internal and volumetric defects but needs radiation-safety controls and is poor at fine cracks lying across the beam. A borescope gives visual access to internal areas.
- Repairs are carried out only to an approved scheme (SRM, AMM or an approved repair design) and within stated limits; SBs and ADs are complied with as mandated, and the work is recorded.
- ⚠ Exam trap: magnetic particle will NOT work on aluminium, it is non-ferromagnetic; use penetrant or eddy current instead.
- Penetrant
- surface-breaking flaws, any non-porous material
- Magnetic particle
- ferromagnetic only, surface / near-surface
- Ultrasonic / radiography
- internal and volumetric defects
A surface crack is suspected in an aluminium fitting. Which NDT methods are suitable, and which is not?
Dye penetrant or eddy current are suitable for a surface crack in aluminium. Magnetic particle is not, aluminium is non-ferromagnetic, so no flux leakage forms and the method cannot work.
Which NDT method would you choose to detect an internal void in a thick component, and what does it require?
Ultrasonic testing, it sends high-frequency sound into the material and times the reflection from an internal defect. It requires a couplant between probe and part, adequate access, and a skilled operator to interpret the trace; radiography is the alternative for volumetric internal defects.
Inspection & NDT concept map
Inspection & NDT
Inspection & NDT quiz
Inspection & NDT, quiz
1. A crack is measured at 0.75 inch. Taking 1 inch as 25.4 mm, its length is:
19.05 mm33.9 mm1.9 mm2. Which NDT method will NOT work on an aluminium component?
Magnetic particleDye penetrantEddy current3. Dye penetrant inspection detects defects that are:
Open to the surfaceDeep internal onlySub-surface in ferrous parts only4. Magnetic particle inspection is limited to:
Ferromagnetic materialsAny conductorNon-metals5. Ultrasonic testing is used to find:
Internal and volumetric defectsOnly surface cracksCorrosion colour6. Ultrasonic testing requires a:
Couplant between probe and partMagnetising currentDeveloper spray7. Eddy-current testing works on:
Conductive materials, surface/near-surfaceNon-conductorsOnly ferrous parts8. Radiographic testing requires particular attention to:
Radiation safetyCouplant selectionMagnetising the part9. A borescope is used to:
Visually inspect internal areasMeasure hardnessMagnetise a part10. Repairs may be carried out only:
To an approved scheme and within limitsBy any method that restores strengthIf no NDT is available11. An airworthiness directive (AD) is:
MandatoryAdvisory onlyOptional after a bulletin12. A surface crack in a steel part is quickly found by:
Magnetic particle inspectionRadiographyWeighing