ISO 9206:2018

INTERNATIONAL ISO
STANDARD 9206
Third edition
2018-12
Aerospace — Fixed displacement
hydraulic motors — General
specifications
Aéronautique et espace — Moteurs hydrauliques à cylindrée fixe —
Spécifications générales
Reference number
©
ISO 2018
© ISO 2018
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Classification . 6
5 General requirements . 6
5.1 Order of precedence . 6
5.2 Hydraulic system characteristics . 7
5.3 Airworthiness regulations . 7
5.4 Qualification . 7
6 Functional requirements . 7
6.1 Hydraulic fluid . 7
6.2 Pressures . 7
6.2.1 Rated supply pressure. 7
6.2.2 Rated differential pressure . 7
6.2.3 No-load break-out pressure . 8
6.2.4 Motor outlet port pressure . 8
6.2.5 Case drain pressure . 8
6.3 Flows . 8
6.3.1 Rated consumption . 8
6.3.2 Case drain flow . 8
6.3.3 Shaft seal leakage flow . 8
6.3.4 External leakage . 9
6.4 Speed and direction of rotation . 9
6.4.1 Speed . 9
6.5 Torque .12
6.5.1 Rated torque .12
6.5.2 Break-out torque .12
6.5.3 Stalling torque .12
6.5.4 Torque pulsations .12
6.6 Motor overall efficiency .12
6.7 Dynamic characteristics .12
6.7.1 General.12
6.7.2 Dynamic braking .12
6.7.3 Rapid reversals .13
6.8 Passive operation .13
6.9 Rated temperature .13
6.10 Acoustic noise level .13
6.11 Rated endurance .13
6.12 Environmental requirements .14
7 Detail design requirements .14
7.1 Dimensionally critical components .14
7.2 Maintainability features .14
7.3 Seals .14
7.4 Lubrication .15
7.5 Balance .15
7.6 Self-contained failure .15
7.7 Safety wire sealing .15
7.8 Electro-conductive bonding .15
7.9 Marking .15
7.9.1 Nameplate .15
7.9.2 Fluid identification .16
7.9.3 Ports .16
8 Strength requirements .16
8.1 General .16
8.2 Proof pressure .16
8.2.1 Motor case .16
8.2.2 Motor inlet port .16
8.2.3 Motor outlet port .16
8.3 Ultimate pressure .17
8.3.1 Motor case .17
8.3.2 Motor inlet port .17
8.3.3 Motor outlet port .17
8.4 Pressure impulse (fatigue) .17
8.5 Port strength .17
9 Construction requirements .17
9.1 Materials .17
9.1.1 General.17
9.1.2 Metals .18
9.2 Corrosion protection .18
9.2.1 General.18
9.2.2 Ferrous and copper alloys .18
9.2.3 Aluminium alloys .19
9.3 Castings .19
10 Installation requirements.19
10.1 Dimensions .19
10.2 Mass .19
10.3 Mounting .19
10.4 Orientation .20
10.5 Coupling shaft .20
10.6 Ports .20
11 Maintenance requirements .20
11.1 Maintenance concept .20
11.2 Service life limitations and storage specifications .21
12 Reliability requirements .21
12.1 Equipment compliance .21
12.2 Requirements .21
13 Quality assurance provisions .21
13.1 Responsibility for inspection .21
13.2 Classification of tests .21
13.3 Test stand requirements .21
14 Acceptance tests .22
14.1 General .22
14.2 Examination of the product .22
14.3 Test programme .22
14.3.1 General.22
14.3.2 External leakage requirements .23
14.3.3 Break-in run .23
14.3.4 Proof pressure and overspeed tests .23
14.3.5 Operational tests at rated conditions .24
14.3.6 Teardown inspection examination .24
14.3.7 Run-in .24
14.3.8 Performance data .25
14.3.9 Fluid contamination test .25
14.3.10 Electro-conductive bonding .26
14.4 Storage and packaging .26
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15 Qualification procedures .26
15.1 General .26
15.2 Qualification procedure .26
15.2.1 Qualification by analogy .26
15.2.2 Motor qualification test report .26
15.2.3 Samples and program of qualification tests .27
15.3 Qualification testing .27
15.3.1 Dimensional check .27
15.3.2 Expanded envelope acceptance tests .28
15.3.3 Overspeed test .28
15.3.4 Operational test at overpressure .28
15.3.5 Calibration .28
15.3.6 Endurance testing .29
15.3.7 Environmental tests .32
15.3.8 Structural tests .33
15.3.9 Supplementary tests .35
Bibliography .36
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 10, Aerospace fluid systems and components.
This third edition of ISO 9206 cancels and replaces the second edition (ISO 9206:2016) which has been
technically revised.
The main changes compared to the previous edition are as follows:
— title replaced “Constant displacement” with “Fixed displacement”;
— deletion of requirement for minimum case drain flow (6.3.2);
— update of external leakage requirements (6.3.4);
— correction of requirement for overspeed (6.4.1.2);
— coupling shaft requirements re-written (10.5);
— the test stand requirements have been revised (13.3);
— requirement to leave the case drain port unplugged in the Inlet port proof pressure test (14.3.4.3)
and the Case port proof pressure test (14.3.4.4);
— update of test procedures in Operational tests at rated conditions (14.3.5);
— revision of the Sampling requirements (14.3.6.1);
— correction of flow measurement in Torque and flow rate (15.3.5.3);
— additional detail provided in the stalling torque and internal leakage test (15.3.5.7);
— endurance test representativity text added (15.3.6.1);
— revision of Endurance test alternating loads test requirements (15.3.6.1 and 15.3.6.3);
vi © ISO 2018 – All rights reserved

— revision of filter used for endurance testing (15.3.6.6);
— revision of Recalibration requirements (15.3.6.9);
— correction of low-temperature test requirement (15.3.7.2);
— clarification of motor operation during vibration tests (15.3.8.1.4);
— clarification of resonant frequency vibration test (15.3.8.1.4);
— ports identified for the ultimate pressure test (15.3.8.5); and
— clarification of coupling shear test (15.3.8.6).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
INTERNATIONAL STANDARD ISO 9206:2018(E)
Aerospace — Fixed displacement hydraulic motors —
General specifications
1 Scope
This document establishes the general requirements for constant displacement hydraulic motors,
suitable for use in aircraft hydraulic systems at pressures up to 35 000 kPa (5 000 psi).
Primary and secondary function motors (see Clause 4) are covered in this document; however, actuators
with internal rotation angle limits and low-speed motors are not covered.
This document is to be used in conjunction with the detail specification that is particular to each
application.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2093, Electroplated coatings of tin — Specification and test methods
ISO 2669, Environmental tests for aircraft equipment — Steady-state acceleration
ISO 2671, Environmental tests for aircraft equipment — Part 3.4 : Acoustic vibration
ISO 2685, Aircraft — Environmental test procedure for airborne equipment — Resistance to fire in
designated fire zones
ISO 3323, Aircraft — Hydraulic components — Marking to indicate fluid for which component is approved
ISO 3601-1, Fluid power systems — O-rings — Part 1: Inside diameters, cross-sections, tolerances and
designation codes
ISO 7137, Aircraft — Environmental conditions and test procedures for airborne equipment
ISO 7320, Aerospace — Couplings, threaded and sealed, for fluid systems — Dimensions
ISO 8078, Aerospace process — Anodic treatment of aluminium alloys — Sulfuric acid process, undyed coating
ISO 8079, Aerospace process — Anodic treatment of aluminium alloys — Sulfuric acid process, dyed coating
ISO 8081, Aerospace process — Chemical conversion coating for aluminium alloys — General purpose
ISO 8399-1, Aerospace — Accessory drives and mounting flanges (Metric series) — Part 1: Design criteria
ISO 8399-2, Aerospace — Accessory drives and mounting flanges (Metric series) — Part 2: Dimensions
ISO 8625-1, Aerospace — Fluid systems — Vocabulary — Part 1: General terms and definitions related to
pressure
ISO 8625-2, Aerospace — Fluid systems — Vocabulary — Part 2: General terms and definitions relating to
flow
ISO 8625-3, Aerospace — Fluid systems — Vocabulary — Part 3: General terms and definitions relating to
temperature
ISO 11218, Aerospace — Cleanliness classification for hydraulic fluids
ISO 16889, Hydraulic fluid power — Filters — Multi-pass method for evaluating filtration performance of
a filter element
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8625-1, ISO 8625-2, ISO 8625-3,
and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1 General
3.1.1
fixed displacement hydraulic motor
mechanical actuator that converts hydraulic pressure and flow into torque and angular velocity
(rotation)
3.1.2
purchaser
organization that has the engineering responsibility for the hydraulic system that includes the motor
Note 1 to entry: Typically, the purchaser is an aircraft manufacturer, an equipment manufacturer that has the
actuation system responsibility or a modification centre.
Note 2 to entry: The purchaser is responsible for the compilation of the detail specification.
3.1.3
detail specification
document compiled by the purchaser (3.1.2) that specifies the following:
a) technical requirements;
b) acceptance and qualification test requirements;
c) reliability requirements;
d) quality requirements;
e) packaging requirements; and
f) other requirements
3.1.4
supplier
organization that provides the motor
Note 1 to entry: Typically, the supplier is the manufacturer of the motor who will be responsible for the design,
production, and qualification of the motor.
3.2 Ports of the hydraulic motor
A fixed displacement hydraulic motor typically achieves bi-directional operation by reversing the
differential pressure across the inlet/outlet ports, thus reversing the output torque. Table 1 below
2 © ISO 2018 – All rights reserved

illustrates the phasing of the motor ports in relation to the motor operation for this application, using
the port identification identifiers listed below.
— port A – motor inlet/outlet port
— port B - motor inlet/outlet port
— port C – motor case drain port
— port D – motor shaft seal port
Table 1 — Phasing of the motor ports in relation to the motor operation
Motor drive coupling Port A Port B Port C Port D
shaft rotation
Clockwise Motor inlet Motor return Case drain Shaft seal
outlet
Counter clockwise Motor return Motor inlet Case drain Shaft seal
outlet
3.2.1
motor inlet port
port that receives flow from the hydraulic system to supply the motor
3.2.2
motor outlet port
port that returns flow back to the system
3.2.3
motor case drain port
port that drains internal leakage flow to the reservoir
3.2.4
shaft seal port
port that routes any shaft seal leakage from the motor to an overboard drain, collector tank, etc.
3.3 Temperature terms
All temperatures are expressed in degrees Celsius.
3.3.1
rated temperature
maximum continuous temperature of the fluid to be supplied at the inlet port of the motor
3.3.2
minimum continuous temperature
minimum temperature of the fluid at the inlet port of the motor at which the motor is able to function
Note 1 to entry: This temperature is generally higher than the survival temperature.
3.3.3
normal operating temperature
temperature of the fluid to be supplied at the inlet port of the motor at which full motor performance is
required
3.4 Pressure terms
3.4.1
design operating pressure
normal maximum steady pressure
Note 1 to entry: Excluded are reasonable tolerances, transient pressure effects such as may arise from the
following:
— pressure ripple;
— reactions to system functioning; and
— demands that may affect fatigue.
3.4.2
rated supply pressure
system rated pressure, which is normally the hydraulic power generation system design operating
pressure (3.4.1)
3.4.3
rated differential pressure
differential pressure measured between the motor inlet and outlet ports required to produce rated
torque (3.8.1)
3.4.4
no-load break-out pressure
differential pressure required for starting the output shaft, without interruption, with the case drain
port at the rated case drain pressure and the outlet port at the rated return pressure
3.4.5 Motor return pressure
3.4.5.1
nominal motor return pressure
pressure generated at the outlet port as the motor returns flow back to the system
3.4.5.2
rated motor return pressure
maximum pressure at the outlet port
Note 1 to entry: This is applicable to uni-directional motors only.
Note 2 to entry: This is a stressing term only as the nominal motor pressure is generally considerably less than
the rated motor return pressure.
3.4.6 Case drain pressure
3.4.6.1
rated case drain pressure
nominal pressure at which the motor case is required to operate continuously in the system
3.4.6.2
maximum case pressure
maximum of either
— the maximum pressure peak that may be imposed by the hydraulic system on the motor case drain
port (3.2.3); or
— the pressure resulting from integral bypassing of the rated flow towards the outlet and drain ports
in order to take into account the accidental transitory separation of the components
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3.5
rated consumption
flow rate measured at the motor inlet port (3.2.1) under conditions of the following:
— rated fluid temperature;
— rated differential pressure (3.4.3);
— rated speed (3.7.1); and
— using the hydraulic fluid specified in the detail specification (3.1.3)
Note 1 to entry: This is typically specified as the maximum flow rate.
3.6
rated displacement
maximum theoretical volume of fluid consumed by one revolution of its output shaft
Note 1 to entry: It shall be expressed in cubic centimetres per revolution (cubic inches per revolution).
Note 2 to entry: The rated displacement shall be calculated from the geometrical configuration of the motor,
without allowing for the effects of the following:
— permissible manufacturing tolerances;
— distortions of the motor structure;
— the compressibility of the hydraulic fluid;
— internal leakage;
— temperature.
Note 3 to entry: The rated displacement is used to indicate the size of the motor rather than its performance.
3.7 Speed terms
3.7.1
rated speed
maximum speed at which the motor is required to operate continuously at rated temperature (3.3.1)
and at rated differential pressure (3.4.3)
Note 1 to entry: The rated speed shall be expressed as the number of revolutions of the motor output shaft
per minute.
3.7.2
maximum no-load speed
speed reached at rated conditions with no opposing torque
3.8 Torque terms
3.8.1
rated torque
minimum torque value at rated operating conditions
3.8.2
break-out torque
minimum torque against which the motor will start at operating conditions specified in the detail
specification (3.1.3)
Note 1 to entry: The specification shall be met at any angular position of the output shaft.
3.8.3
stalling torque
minimum opposing torque which stops the rotation of the outlet shaft at the rated supply pressure
(3.4.2) and for the outlet port and case drain port pressures specified in the detail specification (3.1.3)
3.9
motor overall efficiency
obtained from the formula:
motor overall efficiency (%) = (output shaft power/input fluid power) × 100
where
output shaft power = shaft torque × shaft speed;
input fluid power = (supply pressure – return pressure) × rated flow
Note 1 to entry: This formula ignores compressibility effects. If this formula is to be used, the flow rate
measurement should be made on the compressed flow stream.
3.10
rated endurance
total number of hours and cycles of operation to be included in the endurance phase of its
qualification testing
3.11
first article inspection
process that conducts the following:
— verifies that the parts of a component comply with the drawings;
— verifies that the manufacturing processes have been compiled and are adhered to;
— verifies that the assembly processes have been compiled and are adhered to; and
— verifies that the acceptance test of the component is in accordance with the test procedure, and that
the results of the test are in agreement with the test requirements
4 Classification
The hydraulic motors covered by this document are classified in two categories.
— Category A: Primary function motors, for example, flight controls, slats, flaps, adjustable planes,
transfer units, constant speed drives, etc.
— Category B: Secondary function motors, for example, hoists, guns, radars, doors, etc.
The motor category shall be specified in the detail specification.
5 General requirements
5.1 Order of precedence
The detail specification shall take precedence in the case of a conflict between the requirements of this
document and the detail specification.
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5.2 Hydraulic system characteristics
The hydraulic motor shall be designed to be operated by the hydraulic system as defined in the detail
specification.
The detail specification shall include the characteristics of the hydraulic system in which the motor
is to be used. This shall include the flow versus pressure curves for the supply, return, and case drain
lines for the following hydraulic fluid temperatures:
— normal operating temperature (for example, +20 °C);
— rated temperature; and
— minimum continuous temperature.
5.3 Airworthiness regulations
The hydraulic motor shall meet the applicable civil aviation requirements. Examples of these general
requirements are:
— in the USA: 14 CFR Part 25 § 25.1435;
— in the EU: EASA Certification Specification CS-25 § 25.1435.
5.4 Qualification
Hydraulic motors furnished under this document shall be products that have passed the qualification
tests that are specified in the detail specification.
6 Functional requirements
6.1 Hydraulic fluid
The detail specification shall state the applicable hydraulic fluid.
6.2 Pressures
6.2.1 Rated supply pressure
The value of the rated supply pressure shall be stated in the detail specification and shall be one of the
following values of rated supply pressures listed in Table 2 (derived from ISO 6771).
Table 2 — Rated supply pressure
Pressure Metric system Imperial system
Class kPa basic psi basic
A 4 000 600
B 10 500 1 500
C 16 000 2 500
D 21 000 3 000
E 28 000 4 000
J 35 000 5 000
6.2.2 Rated differential pressure
The rated differential pressure shall be specified in the detail specification.
6.2.3 No-load break-out pressure
The no-load break-out pressure shall be specified in the detail specification.
6.2.4 Motor outlet port pressure
6.2.4.1 Nominal return pressure
The nominal return pressure shall be specified in the detail specification.
6.2.4.2 Rated motor return pressure
The rated motor return pressure (where applicable) shall also be specified in the detail specification.
Unless otherwise specified in the detail specification, the rated motor return pressure shall be
7 000 kPa (1 000 psi).
6.2.5 Case drain pressure
6.2.5.1 Rated case drain pressure
The rated case drain pressure shall be specified in the detail specification.
Caution should be taken defining the rated case drain pressure. Too high a pressure may cause abnormal
shaft seal and shaft bearing loading, affecting their operation and reducing the motor life.
6.2.5.2 Maximum case drain pressure
The maximum case drain pressure shall be specified in the detail specification.
6.3 Flows
6.3.1 Rated consumption
The detail specification shall state the value of the rated consumption, which shall be in l/min (or gpm).
6.3.2 Case drain flow
The motor case flow rate [which shall be in l/min (or gpm)] shall be specified under the following
conditions:
1) the motor turning at rated torque and speed;
2) the motor turning at zero torque; and
3) the motor stalled, shaft locked at any position.
The maximum case drain flow shall be stated at conditions specified in the detail specification.
6.3.3 Shaft seal leakage flow
The detail specification shall state the value of the maximum dynamic shaft seal leakage (which shall
be in drops/min) at the following conditions.
a) New build:
1) the motor filled with fluid, but un-pressurized;
2) when subject to proof pressure at ambient temperature; and
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3) when the motor is operating at rated consumption flow.
b) Qualification testing:
4) over the expanded test envelope;
5) at the completion of the endurance test;
6) when subject to proof pressure at rated temperature; and
7) when subject to ultimate pressure at rated temperature.
6.3.4 External leakage
No leakage sufficient to form a drop from the motor case or from any static se
...