Special characteristics (CC / SC): how to identify and control them
What special characteristics are, what IATF 16949 clause 8.3.3.3 asks for, a severity-based way to classify them, and how they flow into the FMEA, the control plan, capability requirements and the supplier.
Updated 2026-10-28
What a special characteristic is
A special characteristic is a product characteristic or a process parameter whose variation has a particularly strong effect on safety, regulatory compliance, fit, function or the later processing of the part, so that it needs extra attention and control. Customers use their own symbols and names; the idea is the same: not every dimension is equal, and the few that matter most get the strongest controls.
What IATF 16949 asks for
Clause 8.3.3.3 asks for a multidisciplinary process to identify special characteristics, including those set by the customer and those found by your own risk analysis. In short, you have to:
- mark them in the drawings (where required), the risk analysis (FMEA), the control plan and the operator instructions;
- define control and monitoring strategies for each of them;
- use the customer’s definitions and symbols, or your own equivalent symbols with a conversion table that the customer can see.
Always check the customer-specific requirements: the symbols, the classes and the capability targets differ between OEMs.
A severity-based starting rule
If the customer gives no rule, a common starting point from the FMEA is the severity of the effect of failure:
| Severity | Effect | Class |
|---|---|---|
| 9–10 | Safety or regulatory compliance affected | Critical (CC) |
| 7–8 | Loss of primary function, or fit and function with high customer impact | Significant (SC) |
| 1–6 | Minor effects | Not special |
The FMEA-to-control-plan conversion in this site uses exactly this rule as a draft, and you adjust it to the customer’s definitions. Also look at characteristics with a high occurrence and a medium severity: they do not become special by the table, but they are often where complaints come from.
What changes for a special characteristic
- Capability: a higher requirement, typically Ppk ≥ 1.67 in the initial study and Cpk ≥ 1.33 in series, unless the customer says otherwise (see PPAP capability requirements).
- Control method: SPC with a defined reaction plan, error proofing, or 100 % inspection when capability cannot be reached yet.
- Measurement system: an accepted Gage R&R before the data are trusted.
- Records and traceability: measured values kept for the required retention period.
- Suppliers: the characteristic and the requirement are passed on in the drawing and the quality agreement.
Keep the list short and consistent
Too many special characteristics dilute the effort: if everything is special, nothing is. Review the list at every design change and after complaints. The same characteristic must carry the same symbol in the FMEA, the control plan, the work instruction and the drawing; an audit finds the mismatch immediately.
Common mistakes
- The customer’s symbol is in the drawing but missing in the control plan.
- No capability data for a characteristic marked as special.
- Special characteristics identified once during APQP and never updated.
- The supplier receives the drawing but not the capability requirement.