ISO 6771:2007

INTERNATIONAL ISO
STANDARD 6771
Third edition
2007-08-15
Aerospace — Fluid systems and
components — Pressure and temperature
classifications
Aéronautique et espace — Systèmes de fluides et éléments
constitutifs — Classification des températures et des pressions

Reference number
©
ISO 2007
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ii © ISO 2007 – All rights reserved

Foreword
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(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
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International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
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ISO 6771 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.
This third edition cancels and replaces the second edition (ISO 6771:1987), which has been technically
revised. This third edition adds imperial unit equivalents, and the nominal temperatures and pressures for all
classes have been revised.
Introduction
Aerospace fluid systems and components are generally designed and marked for a specific fluid pressure
class and temperature type.
iv © ISO 2007 – All rights reserved

INTERNATIONAL STANDARD ISO 6771:2007(E)

Aerospace — Fluid systems and components — Pressure and
temperature classifications
1 Scope
This International Standard specifies the pressure classes and temperature types for the basic systems and
component systems that are commonly used in aerospace fluid systems. Classes and types in the lower ranges
represent systems in common use. Those in the higher ranges represent systems that are in less common use
or that are used in developmental systems.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
basic system
temperature types and pressure classes of the aircraft fluid systems, usually specified in the aircraft
specification, with which the vehicle is designed to be operated
NOTE 1 The basic system consists of several subsystems.
NOTE 2 The temperature type and pressure classes are tested and certified as an integral part of vehicle performance.
2.2
component system
system whose temperature types and pressure classes are usually defined in the product specification
NOTE 1 The components are tested and qualified individually under each subsystem.
NOTE 2 The harmonization of temperature and pressure tolerances is accomplished in the component systems so that
one product can be used in both systems, metric or imperial, and attain the same degree of performance of the
subsystem.
3 Classification
3.1 Basic system
3.1.1 General
The pressure classes and temperature types for the basic systems are as specified in Tables 1 and 2. No
tolerance is permitted in the basic systems.
3.1.2 Pressure classes
Nominal system pressure classes for the basic systems shall be as specified in Table 1. The old pressure
classes designated in Table 1 are the existing systems commonly used in the United States and Europe
...