Critical Characteristic (CC)

A Critical Characteristic (CC) is a specific product or process attribute that is identified as having a significant impact on safety, regulatory compliance, or the fit, form, or function of a part or assembly. In regulated manufacturing environments such as aerospace, defense, and medical devices, CCs are formally called out, controlled, and verified to reduce the risk of severe failures.

What a Critical Characteristic includes

A Critical Characteristic commonly refers to any measurable feature where an out-of-tolerance or incorrect condition could:

• Compromise safety or airworthiness
• Violate a regulatory, contractual, or customer requirement
• Prevent the part from meeting required fit, form, or function
• Cause loss of performance that is not easily detectable in service

Examples in an industrial context include:

• Critical dimensions and tolerances (hole diameter, wall thickness, concentricity)
• Material or heat-treatment requirements (alloy type, hardness, temper condition)
• Special process parameters (plating thickness, weld penetration, cure time/temperature)
• Software or configuration items that affect control logic or safety interlocks

Operational meaning on the shop floor

In operations and quality systems, Critical Characteristics are typically:

• Identified in drawings, specifications, control plans, and FMEA outputs
• Ballooned and numbered in inspection plans and AS9102 First Article Inspection (FAI) reports
• Tagged in MES, QMS, or PLM systems for special handling and traceability
• Subject to enhanced inspection, measurement system analysis, and documented acceptance criteria
• Linked to specific process controls, operator qualifications, or special process approvals

Recording results for CCs is often required at the characteristic level, with clear traceability to the lot, work order, operator, equipment, and inspection gage used.

Relationship to risk and compliance

CCs are usually identified through risk-based methods such as FMEA, hazard analysis, or regulatory assessments. Once identified, they are managed through:

• Control plans that specify how the characteristic is produced and verified
• Documented inspection plans, sampling strategies, and acceptance criteria
• Nonconformance and CAPA workflows when CCs are found out of specification
• Evidence records used for audits, customer reviews, and regulatory inspections

Common confusion

Critical Characteristic vs. Key Characteristic (KC)

Both terms refer to important product or process features, but they are not always interchangeable:

• Critical Characteristic (CC): Typically tied to safety, regulatory, or functional risk. Failure can have severe consequences and often triggers stricter controls and traceability.
• Key Characteristic (KC): Often used for features that strongly influence product performance, manufacturability, or variation control, but may not always be directly safety-related.

Specific industries, customers, or standards may define these terms differently. It is common to find organization- or customer-specific definitions for CCs in quality manuals, procedures, or contracts.

Connection to aerospace and AS9102

In aerospace manufacturing, Critical Characteristics are frequently identified on engineering drawings and then carried into AS9102 First Article Inspection documentation. Each CC is ballooned, numbered as an inspection characteristic, and must have documented results. Digital FAI and MES systems often represent CCs explicitly to support traceability, inspection evidence, and audit readiness across the product lifecycle.