1. Scope
This procedure covers liquid penetrant examination (PT) of aerospace fasteners (high-tensile bolts, threaded fittings, and machined fastener forgings) using fluorescent (Type I) and visible-dye (Type II) penetrants in accordance with ASTM E165 / E165M and aerospace prime supplements (typically Boeing BAC 5424, Lockheed STP57-100, Airbus AITM 6-4001). Materials: precipitation-hardened stainless, titanium alloys (Ti-6Al-4V, Ti-5Al-2.5Sn), aluminum alloys, and high-strength low-alloy steels. Stress-corrosion-sensitive alloys (titanium, austenitic stainless, high-nickel) require halogen-and-sulfur-controlled penetrant chemistries per ASTM F519 supplement.
2. References
- ASTM E165 / E165M — Standard Practice for Liquid Penetrant Examination
- ASTM E1417 / E1417M — Standard Practice for Liquid Penetrant Testing
- ASTM E1209 / E1219 — Sensitivity-level qualification
- SAE AMS-2644 — Inspection Material, Penetrant
- NAS 410 / EN 4179 — Personnel qualification
- Customer Written Practice and aerospace prime PCD
3. Personnel Qualification
PT examination shall be performed by personnel certified to NAS 410 Level II in PT (or EN 4179 equivalent), with the prime-contractor procedure-specific authorization on file. Level III review per the customer's primary qualification chain.
4. Penetrant Material
Penetrants, removers, and developers shall be sourced from the same manufacturer's product family certified to AMS 2644 Level 3 (High) or Level 4 (Ultra-high) sensitivity for aerospace fastener work. Type I (fluorescent), Method A (water-washable) is the most common combination; Method C (post-emulsifiable) may be specified for surface-roughness conditions. Each batch must carry a Certificate of Analysis verifying:
- Halogen content < 25 ppm (for titanium, austenitic, and Ni-base service)
- Sulfur content < 25 ppm (for the same)
- AMS-2644 batch sensitivity grade
5. Surface Preparation
Fasteners shall be vapour degreased (Type I trichloroethylene or AMS-2644-compatible alternative) and dried before penetrant application. Mechanical surface treatments — shot peening, grit blast, machining — shall be performed prior to PT or the surfaces shall be acid-etched to remove smear that masks indications. Plating, painting, or chemical conversion coatings must be removed in the inspection area.
6. Process Parameters
6.1 Temperature Range
Penetrant application: 10 °C (50 °F) to 38 °C (100 °F). For excursion outside this range, a comparator block per ASTM E1208 shall be processed alongside the production lot.
6.2 Penetrant Application
Spray, brush, dip, or immersion. Full and continuous wetting of the surface and threads. Dwell time: 10 minutes minimum, 30 minutes maximum (Type I, Method A). Longer dwell required for tight cracks in machined surfaces — refer to ASTM E1417 Table 1.
6.3 Excess Penetrant Removal
Method A (water-washable): wash with low-pressure (≤ 40 psi / 280 kPa) water spray at 10-38 °C. UV inspection during wash to prevent over-wash — stop when the part background reaches uniform dark (Type I).
6.4 Drying
Forced air at ≤ 71 °C (160 °F), time as needed to remove residual moisture — typically 5-10 minutes. Over-drying degrades indication formation.
6.5 Developer Application
Non-aqueous wet developer (Form D) is preferred for aerospace fastener work; aqueous suspendible (Form B) acceptable for batch processing. Apply as a fine, even mist — heavy developer films mask fine indications. Developer dwell: 10 minutes minimum, 60 minutes maximum.
7. Examination
7.1 Type I (Fluorescent)
UV-A intensity at the examination surface: ≥ 1000 µW/cm² measured with a calibrated UV-A radiometer. Ambient white light at the inspection booth: ≤ 20 lux (2 fc). Inspector eye adaption: minimum 1 minute in darkroom.
7.2 Type II (Visible Dye)
Minimum 500 lux (50 fc) white-light illumination at the examination surface. Inspection performed under uniform light.
7.3 Magnification
Aerospace fastener examination shall be performed with 3× to 10× magnification for the thread roots and underhead fillet, per the prime PCD.
8. Acceptance Criteria
Per the applicable aerospace prime PCD — typical fastener acceptance:
- No crack-like indication permitted in the underhead fillet radius.
- No crack-like indication permitted in the thread root.
- Rounded indication on shank: maximum 0.4 mm (0.015 in), isolated.
- Linear indication length-to-width ratio ≥ 3 — rejectable.
- Cluster of three or more rounded indications in a 6 mm length — rejectable.
9. Reporting
Per ASTM E1417 §10 — minimum: part number, lot number, serial number where applicable, material, processing date, penetrant material identity and batch, comparator block readings, examiner name and NAS 410 cert number, Level III sign-off, and disposition (accept / reject) of each indication. Records retained per prime contractor PCD — typically design life of the airframe.
10. Safety
Penetrants and removers contain organic solvents — local-exhaust ventilation required at application and removal stations. UV-A inspection requires UV-blocking eyewear and skin coverage. Halogen and sulfur control protocols per AMS 2644 — segregation of inspection materials approved for titanium / austenitic stainless service.
This procedure is a published reference. Production use requires aerospace prime-specific PCD approval. Generate a custom fastener-PT procedure including the prime's exact dwell, wash, and acceptance limits at the free AI Procedure Generator.