EN 2257:1997

Overview

EN 2257:1997 (published by CEN) is an aerospace-series standard that specifies the dimensions and tolerances for circular tubes used in aerospace structures made from aluminium and aluminium alloys. The standard covers nominal diameters from 6 mm to 100 mm and wall thicknesses from 1 mm to 6 mm. It has been adopted nationally (for example as SIST EN 2257:2001 in Slovenia) and is intended to ensure dimensional interchangeability and consistent quality for structural tubing in aerospace applications.

Key topics and requirements

• Scope and applicability: Defines which circular aluminium tubes are covered (structural use in aerospace) and the range of nominal diameters and wall thicknesses.
• Dimensional requirements: Establishes nominal dimensions and acceptable dimensional variations (tolerances) for outer diameter and wall thickness within the stated ranges.
• Tolerance classes and measurement: Provides the framework for inspection and measurement of tube dimensions to ensure compliance with the standard.
• Identification and documentation: Requires appropriate identification of tube items and documentation to demonstrate conformity (e.g., dimension certificates, traceability).
• Compatibility with aluminium alloys: Applies to tubes manufactured from aluminium and aluminium alloys commonly used in aerospace; material-specific mechanical properties are covered by separate material standards.
• Relevant classification codes: Linked to ICS categories for aerospace fluid systems and components (49.080) and aluminium (49.025.20).

Note: EN 2257 focuses on geometric and dimensional aspects. It does not itself prescribe specific alloy compositions or mechanical properties - those are addressed by material specifications and other standards.

Applications

• Aerospace structural components: Selection and procurement of circular aluminium tubing for airframe structures, subassemblies, supports and secondary structures.
• Design and engineering: Ensures designers can specify tube sizes with confidence that manufacturers will meet standardized dimensions and tolerances.
• Manufacturing and quality control: Used by tube producers, fabricators, and inspection teams to verify dimensional conformity during production and incoming inspection.
• Procurement and supply chain: Enables buyers and suppliers to reference a common dimensional standard for contracts and part acceptance.

Who uses this standard

• Aerospace designers and structural engineers
• Tube manufacturers and extrusion/welding shops
• Quality assurance and inspection personnel
• Purchasing and supply chain managers in aerospace OEMs and Tier suppliers
• Certification and regulatory bodies verifying component compliance

Related standards

• Other CEN/EN standards for aluminium material specifications and mechanical property requirements
• Standards for dimensional tolerances, testing and inspection methods used in aerospace manufacturing
• National adoptions such as SIST EN 2257:2001

Keywords: EN 2257, circular aluminium tubes, aerospace tubing, aluminium alloy tubes, dimensions and tolerances, diameter 6-100 mm, wall thickness 1-6 mm, CEN standard, SIST EN 2257.