Compliance · 6 min read
AS9100 Calibration Requirements, Explained
AS9100 doesn’t tell you how often to calibrate a caliper — it tells you to prove your measurements can be trusted. This guide walks through what clause 7.1.5 requires, what aerospace customer auditors actually check, and how to keep your calibration program off the findings list.
Where calibration lives in AS9100
AS9100 (Rev D) addresses calibration in clause 7.1.5, “Monitoring and Measuring Resources.” The requirement is outcome-driven: when you use measurement to verify product conformity, the measuring equipment must be suitable, maintained, and — where measurement traceability is required — calibrated or verified at planned intervals against standards traceable to national or international standards. Where no such standard exists, the basis used must be recorded.
The clause also requires equipment to be identified (so its calibration status is knowable), safeguarded from adjustments that would invalidate results, and protected from damage. And critically: when equipment is found out of tolerance, you must assess the validity of previous measurements made with it and take appropriate action on any product affected — the “reverse traceability” exercise auditors love to probe.
What aerospace customer auditors actually check
Registrar and customer-quality audits rarely stop at “is there a sticker.” Common threads they pull: whether the calibration certificate shows traceability and data (not just PASS), whether intervals are justified rather than arbitrary, whether out-of-tolerance conditions triggered a documented impact assessment, and whether the calibration supplier itself is competent.
That last point is where supplier selection matters. ISO/IEC 17025 accreditation is the recognized evidence of a calibration lab’s competence, and many aerospace primes flow down requirements referencing ANSI/NCSL Z540.3 — which brings decision rules and false-accept risk into play. Certificates from American Gage document as-found/as-left data, measurement uncertainty, NIST traceability, and the Z540.3 decision rule with test uncertainty ratio (TUR), under A2LA accreditation (certificate 4296.01).
A checklist that survives an AS9100 audit
A calibration program that holds up typically has these elements in place:
- A controlled equipment list with unique IDs, locations, and calibration status
- Documented intervals with a rationale (manufacturer guidance, usage, as-found history)
- Certificates with data, uncertainty, and traceability from an ISO/IEC 17025-accredited supplier
- A documented out-of-tolerance / impact-assessment procedure — with records showing it was actually used
- Safeguards against unauthorized adjustment (seals, restricted menus)
- Recall / due-date tracking so nothing measures product while overdue
Common questions
Does AS9100 require an ISO 17025 accredited calibration supplier?
AS9100 itself requires traceable calibration and competent processes; many aerospace customers and primes contractually require ISO/IEC 17025-accredited suppliers, and auditors treat accreditation as the standard evidence of competence. Check your customer flow-downs — and using an accredited lab removes the argument entirely.
What happens if an instrument is found out of tolerance?
Clause 7.1.5 requires you to determine whether previous measurement results were affected and take appropriate action — which can mean re-inspecting product back to the last good calibration. As-found data on your certificates is what makes that assessment possible.
How are calibration intervals set under AS9100?
The standard requires calibration at planned intervals but leaves the interval to you — justified by manufacturer guidance, usage severity, and as-found history. Shortening intervals for tools that repeatedly drift, and documenting why, is exactly what auditors want to see.