--- title: "Aerospace Special Process Approvals Guide | TEK Precision" url: https://tekprecision.com/blog/special-process-approvals-aerospace-suppliers description: "Compare special process approvals before you choose an aerospace supplier. What each approval means, what to verify and what to ask." lang: en --- Image: Adhesive bonding room at TEK Precision with an observation window and work cabinets (https://tekprecision.com/assets/sikorsky-bonding-room-DgDDAjPA.webp) All Articles (https://tekprecision.com/blog) Buyer Guides # Aerospace Special Process Approvals: What Buyers Should Verify Before Choosing a Supplier TEK Precision October 9, 2026 5 min read Compare special process approvals before you choose an aerospace supplier. What each approval means, what to verify and what to ask. A special process approval tells you that a customer or an accreditation body has examined how a supplier controls a process whose results cannot be fully checked by inspecting the finished part. To compare suppliers, check who granted the approval, exactly what it covers, whether it is current, and whether the work is done in-house or subcontracted. This guide explains what counts as a special process, the kinds of approval you will see, and the questions that separate a real capability from a certificate on the wall. ## What counts as a special process A special process is one where the output cannot be verified by later inspection or measurement. Quality standards require such processes to be validated before use and revalidated periodically. AS9100D, which is built on ISO 9001, includes this requirement. Common aerospace examples include heat treatment, structural adhesive bonding, nondestructive testing, welding, coatings and chemical processing. A bonded joint or a heat-treated surface can look identical whether it was done correctly or not, so the quality has to be built in through process control rather than found by inspection. ## The kinds of approval you will see - **Quality system certification (AS9100D / ISO 9001).** An accredited registrar audits the supplier's management system. It shows that a system exists, but it does not approve any particular process. - **Customer approval.** Some OEMs approve suppliers directly against their own specifications. For example, Sikorsky specification SS8669 governs structural adhesive bonding, and a supplier can be approved for some of its classes and not others. - **Industry accreditation (Nadcap).** Nadcap is an industry-managed accreditation program run by the Performance Review Institute. It covers special processes such as heat treating, nondestructive testing, welding, coatings and chemical processing. Whether it is required depends on the prime contractor and the process, so read your drawing, purchase order and flow-downs. - **Personnel qualification.** Some specifications also require the people to be qualified. Under SS8669, bonding operators are individually qualified, and SS8705 requires temper etch examiners to be individually certified. ## What to verify before you approve a supplier - **Who granted it, and to which specification.** Ask for the specification and revision by name, not just "approved". - **What it covers.** Check the processes, classes and materials in scope. An approval for some classes does not cover the others. - **Whether it is current.** Ask when the approval was last audited and when it renews. - **Where the work is done.** Ask which special processes are performed in-house and which are subcontracted, and how any subcontracted processor is approved. - **Who does the work.** Ask whether operators and examiners are individually qualified and how that qualification is kept current. - **What is recorded.** Process parameters and results should be recorded for each lot, not just a pass or fail. - **How the process is verified.** Ask how the supplier confirms the process was in control on the day, for example with test panels or etch checks. The last two questions are the ones suppliers find hardest to answer. Our guide to evaluating an aerospace machining supplier (https://tekprecision.com/blog/how-to-evaluate-aerospace-machining-supplier) covers the wider checklist. ## Why in-house capability matters When a special process is subcontracted, parts leave the building, results come back later and traceability has one more place to break. Two examples show the difference. Structural adhesive bonding relies on test panels that are tensile tested to confirm the process was in control. If the panels are sent out and one fails, the hardware bonded in that window is already downstream. We explain this in What SS8669 All-Class Bonding Approval Actually Means (https://tekprecision.com/blog/ss8669-structural-adhesive-bonding-explained). Temper etch inspection finds grind burn, which dimensional checks cannot see. With the etch done in-house, a burn indication is a same-shift signal: grinding can stop and the cause can be found while the affected group of parts is still small. See Grind Burn: The Defect You Cannot See (https://tekprecision.com/blog/grind-burn-detection-nital-etch-inspection). Watch for these warning signs: - An approval described only as "certified", with no specification, scope or date. - Special processes sent out with no explanation of how the processor is approved. - Results kept only as pass or fail, with no recorded parameters. - No named qualified operators or examiners for a process that requires them. ## Special process approvals at TEK Precision TEK Precision's approved special processes are nital etch inspection, adhesive bonding (all classes), hardness testing, stress relieving, tensile testing and conductivity inspection. You can see them on our Quality page (https://tekprecision.com/quality#approvals). For structural adhesive bonding, we are approved for all classes of Sikorsky SS8669. Bonding takes place in an environmentally controlled room, with certified bonding operators, full traceability per Sikorsky SSQR, and tensile and etch verification carried out in-house. We perform temper etch inspection per SS8705 in-house with certified nital etch examiners, and hardness inspection in-house to ASTM E-10, E-18, E-92 and E-384. See our guide to choosing the right hardness test (https://tekprecision.com/blog/hardness-testing-methods-aerospace-parts). Thermal stress relief is available in-house per SS8407 and SS8669. Operator and inspector certifications are kept under our documented quality system, with training records tied to each special process approval. Procurement teams can request audit documentation or schedule a facility quality audit through our contact page (https://tekprecision.com/contact). ## Frequently asked questions **What is a special process in aerospace?** It is a process whose output cannot be fully verified by later inspection or measurement, such as heat treatment, bonding, welding or nondestructive testing. Its quality depends on controlling the process itself. **Is Nadcap required?** It depends on the prime contractor and the process. Some customers require Nadcap accreditation for certain processes, while others approve suppliers against their own specifications. Check the drawing, purchase order and flow-downs. **Does an AS9100D certificate cover special processes?** AS9100D requires a supplier to control its special processes, but the certificate alone does not tell you which processes a customer has approved or to which specification. Ask for the approval itself. **Why does in-house capability matter?** Fewer transfers mean fewer places for traceability to break, and results arrive faster, so a drifting process is caught while fewer parts are affected. **How do I compare two suppliers' approvals?** Ask each for the same things: the specification and revision, the scope, the last audit date, whether the work is in-house, and the records kept per lot. **Related capabilities:** Quality credentials and approvals (https://tekprecision.com/quality#approvals) · Inspection and test equipment (https://tekprecision.com/quality#inspection-lab) · Machining capabilities (https://tekprecision.com/products#machining-capabilities) _Discuss a program or audit requirement: https://tekprecision.com/contact._ TP Written by TEK Precision Related Articles ## More from Buyer Guides Buyer Guides ### Turnkey Mechanical Assemblies: What Tier-1 OEMs Gain From One Qualified Source October 9, 2026 https://tekprecision.com/blog/aerospace-mechanical-assembly-supplier-guide Buyer Guides ### What to Include in an Aerospace RFQ September 30, 2026 https://tekprecision.com/blog/aerospace-rfq-checklist Buyer Guides ### How to Evaluate an Aerospace Machining Supplier September 30, 2026 https://tekprecision.com/blog/how-to-evaluate-aerospace-machining-supplier ## Structured data ```json [ { "@context": "https://schema.org", "@graph": [ { "@type": "Organization", "@id": "https://tekprecision.com/#organization", "name": "TEK Precision Co., Ltd.", "alternateName": "TEK Precision", "url": "https://tekprecision.com/", "logo": { "@type": "ImageObject", "url": "https://tekprecision.com/brand/tek-logo.webp" }, "foundingDate": "1968", "description": "Precision aerospace manufacturer of flight safety-critical components, hydraulic assemblies and mechanical assemblies for rotorcraft and fixed-wing platforms.", "email": "teksales@tekprecision.com", "telephone": "+1-631-242-0330", "address": { "@type": "PostalAddress", "streetAddress": "205 West Industry Court", "addressLocality": "Deer Park", "addressRegion": "NY", "postalCode": "11729", "addressCountry": "US" }, "sameAs": [ "https://www.linkedin.com/company/tek-precision/" ], "hasCredential": { "@type": "EducationalOccupationalCredential", "credentialCategory": "certification", "name": "AS9100D / ISO 9001:2015", "identifier": "275724", "description": "AS9100D / ISO 9001:2015 certified. 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