ISO 11218-2017 PDF

Full title and description

ISO 11218:2017 — Aerospace — Cleanliness classification for hydraulic fluids. This International Standard specifies a cleanliness classification system intended for hydraulic fluids used in aeroplanes, helicopters and space vehicles; it provides concise classification guidance for use in procurement, maintenance and quality-control activities within aerospace hydraulic systems.

Abstract

ISO 11218:2017 specifies a cleanliness classification for hydraulic fluids in aeroplanes, helicopters and space vehicles. The document is short (informative/classification type) and gives a standardized way to express fluid cleanliness for aerospace applications.

General information

• Status: Published (International Standard; confirmed on review).
• Publication date: February 16, 2017 (Edition 2, 2017).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 49.080 (Aerospace systems and components).
• Edition / version: Edition 2 (2017).
• Number of pages: 2 pages (short classification standard).

(General information above is taken from the ISO bibliographic entry for ISO 11218:2017; the publication was subject to ISO systematic review and was confirmed in 2022.)

Scope

ISO 11218:2017 provides a cleanliness classification specifically for hydraulic fluids intended for aerospace use — aircraft (aeroplanes and helicopters) and space vehicles. It is intended to standardize how cleanliness requirements and cleanliness levels are specified and communicated between suppliers, maintenance organisations and system integrators in the aerospace domain.

Key topics and requirements

• Definition of a concise cleanliness classification applicable to aerospace hydraulic fluids.
• Application scope limited to aeroplanes, helicopters and space vehicles (aerospace hydraulic systems).
• Intended use for procurement, acceptance criteria and maintenance reporting of fluid cleanliness.
• Alignment with established aerospace cleanliness practices and historical reference to SAE/industry cleanliness classifications (AS4059 / NAS heritage), used to enable consistent interpretation across organisations.
• Short, classification-style standard (no extensive test procedures contained — references and cross‑reference to particle-counting / calibration standards are typically used in practice).

Typical use and users

Typical users are aerospace engineers, hydraulic-system designers, maintenance and overhaul organisations, procurement and quality teams, component suppliers, test laboratories and regulators who need a standardized way to specify and communicate hydraulic-fluid cleanliness for aerospace equipment. The standard is used when writing procurement specifications, acceptance criteria after maintenance, or to document allowable contamination levels in system refurbishment and testing activities.

Related standards

Standards commonly used alongside ISO 11218:2017 include SAE AS4059 (Aerospace cleanliness classification for hydraulic fluids) and particle-counting / coding and calibration standards such as ISO 4406 (coding of contamination level by solid particles) and ISO 11171 (calibration of automatic particle counters). Older/related historical cleanliness systems include NAS 1638; these documents are frequently cross-referenced when specifying or measuring fluid cleanliness.

Keywords

aerospace, hydraulic fluids, cleanliness classification, fluid contamination, particle count, AS4059, ISO 4406, aerospace maintenance, fluid procurement

FAQ

Q: What is this standard?

A: ISO 11218:2017 is an international standard titled "Aerospace — Cleanliness classification for hydraulic fluids" that provides a concise cleanliness classification system for hydraulic fluids used in aeroplanes, helicopters and space vehicles.

Q: What does it cover?

A: It covers the classification (nomenclature/levels) of hydraulic-fluid cleanliness for aerospace applications — i.e., how to express allowable contamination levels and thereby communicate cleanliness requirements between suppliers, maintainers and manufacturers. It is a short classification standard rather than a detailed test-method specification.

Q: Who typically uses it?

A: Aerospace engineers, hydraulic-system designers, maintenance/overhaul organisations, procurement and quality assurance teams, component suppliers and test laboratories involved with aerospace hydraulic systems typically use ISO 11218 to specify or interpret fluid cleanliness requirements.

Q: Is it current or superseded?

A: ISO 11218:2017 (Edition 2) is published and was confirmed at systematic review in 2022; it remains the current edition (it replaced the earlier ISO 11218:1993).

Q: Is it part of a series?

A: ISO 11218 is a standalone, short classification standard within the broader family of hydraulic-fluid and contamination-control standards. It is typically used together with particle-counting and calibration standards (for example ISO 4406 and ISO 11171) and with industry aerospace cleanliness documents such as SAE AS4059.

Q: What are the key keywords?

A: Aerospace; hydraulic fluid; cleanliness; contamination; particle count; AS4059; ISO 4406; fluid procurement; maintenance acceptance.