ISO 8278:2016

DRAFT INTERNATIONAL STANDARD ISO/DIS 8278
ISO/TC 20/SC 10 Secretariat: DIN
Voting begins on Voting terminates on

2013-04-16 2013-07-16
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION  •  МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ  •  ORGANISATION INTERNATIONALE DE NORMALISATION


Aerospace — Hydraulic, pressure compensated, variable
delivery pumps — General requirements
Aéronautique et espace — Pompes hydrauliques à débit variable régulé en fonction de la pression —
Exigences générales
[Revision of first edition (ISO 8278:1986)]
ICS 49.080









To expedite distribution, this document is circulated as received from the committee
secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at
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Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
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THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
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©  International Organization for Standardization, 2013

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ISO/DIS 8278

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©  ISO 2013
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ISO/DIS 8278
Contents Page
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 7
5 Functional requirements . 7
6 Detail design requirements . 19
7 Strength requirements . 21
8 Construction requirements . 23
9 Installation requirements . 25
10 Maintenance requirements . 26
11 Reliability requirements . 26
12 Quality assurance provisions . 27
13 Acceptance tests . 28
14 Qualification tests . 32

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ISO/DIS 8278
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
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
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 8278 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.
This second edition cancels and replaces the first edition and also ISO 12334: 2000; the entire document has
been rewritten and it incorporates requirements from ISO 12334.

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DRAFT INTERNATIONAL STANDARD ISO/DIS 8278

Aerospace series — Hydraulic, pressure compensated, variable
delivery pumps — General requirements
1 Scope
This International Standard establishes the general requirements for pressure compensated, variable delivery
hydraulic pumps, suitable for use in aircraft hydraulic systems at pressures up to 35 000 kPa (5 000 psi).
This International Standard shall be used in conjunction with detail specifications that is particular to each
application.
2 Normative references
The following referenced documents are indispensable for the application 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 systems — O-rings — Part 1: Inside diameters, cross-sections, tolerances and designation
codes
ISO 6771, Aerospace — Fluid systems and components — Pressure and temperature classifications
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
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ISO/DIS 8278
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
3 Terms and definitions
For the purposes of this document the terms and definitions given in ISO 8625-1, ISO 8625-2 and ISO 8625-3
and the following apply.
3.1
variable delivery, hydraulic pump
self-regulating hydraulic pump that supplies hydraulic power to the hydraulic system (or sub-system) at a
nominal constant pressure
Note 1 to entry: The pump can be driven by a variety of power sources, including:
 by an engine via an accessory gearbox;
 electric motor;
 pneumatic power drive.
3.2
purchaser
organization that has the engineering responsibility for the hydraulic system that includes the pump
Note 1 to entry: Typically, the purchaser is an aircraft manufacturer, an equipment manufacturer that has hydraulic
system responsibility or a modification centre.
Note 2 to entry: The purchaser is responsible for the compilation of the detail specification.
3.3
detail specification
the document compiled by the purchaser that specifies the following:
a) technical requirements;
b) acceptance and qualification test requirements;
c) reliability requirements;
d) quality requirements;
e) packaging requirements;
f) other requirements
3.4
supplier
manufacturer of the pump who will be responsible for the design, production and qualification of the pump
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ISO/DIS 8278
3.5
ports of the hydraulic pump
3.5.1
pump inlet port
port that receives flow from the hydraulic reservoir to supply the pump
3.5.2
pump discharge port
port that supplies pressurised flow to the system
3.5.3
pump case drain port
port that drains internal leakage flow to the reservoir
3.5.4
shaft seal port
port that routes any shaft seal leakage from the pump to an overboard drain, collector tank etc.
3.6
temperature terms
3.6.1
rated temperature
maximum continuous temperature of the fluid to be supplied at the supply port of the pump
Note 1 to entry: The rated temperature is expressed in degrees centigrade.
3.6.2
minimum continuous temperature
minimum continuous temperature of the fluid to be supplied at the supply port of the pump
Note 1 to entry: The minimum continuous temperature is expressed in degrees centigrade.
3.7
pressure terms
3.7.1
design operating pressure
normal maximum steady pressure
Note 1 to entry: Excluded are reasonable tolerances, transient pressure effects such as may arise from:
 pressure ripple;
 reactions to system functioning;
 demands that may affect fatigue.
3.7.2
inlet pressure
3.7.2.1
rated inlet pressure
minimum pressure measured at the inlet port of the pump at which the pump is required to provide
performance without any degradation, with all other parameters at their rated values, except for the fluid
temperature, which is the minimum continuous temperature
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ISO/DIS 8278
3.7.2.2
maximum inlet pressure
maximum steady state inlet pressure at which the pump may be required to operate
3.7.2.3
minimum inlet pressure
lowest pump inlet port pressure, specified by the purchaser, for which the supplier ensures that the pump
might be required to operate without cavitation during a system failure or during a system high-flow transient
condition
Note 1 to entry: For the purposes of this International Standard, cavitation is assumed to occur when there is a 2 %
reduction in discharge flow with reducing inlet pressure.
3.7.3
discharge pressure
maximum pressure against which the pump is required to operate continuously at rated temperature, at rated
speed and at zero flow (see Figure 1)
Note 1 to entry: This diagram is given as an indication. It may be presented in a different way, for example, the axes
may be reversed.

Key
1 Actual discharge/pressure characteristic curve
2 At p , q > q
M A N
p pressure
p maximum full-flow pressure (see 3.7.3.1)
M
p rated discharge pressure
N
a
p tolerance range
N
q discharge flow
q actual discharge at maximum full-flow pressure
A
q rated discharge flow (see 3.8)
N
Figure 1 — Delivery/pressure characteristic curve of pumps
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ISO/DIS 8278
3.7.3.1
maximum full-flow pressure
maximum discharge pressure at which the pump control will not be acting to reduce pump discharge, at rated
temperature, rated speed, rated inlet and case drain pressure
3.7.3.2
maximum pump discharge transient pressure
peak value of the discharge pressure recorded during a discrete transient event (normally found whilst cycling
from full flow pressure to rated pressure (zero flow))
3.7.3.3
pressure pulsations
oscillations of the pump discharge pressure, occurring during nominally steady operating conditions, at a
frequency equal to the number of pistons times the drive shaft speed, or a multiple thereof
Note 1 to entry: The amplitude of the oscillations is the difference between the average minimum and the average
maximum oscillations recorded during a one-second trace.
3.7.4
case drain pressure
3.7.4.1
maximum case drain pressure
maximum continuous pressure developed by the pump to enable case drain fluid to return to the reservoir
3.7.4.2
rated case drain pressure
nominal pressure at which the pump case is required to operate continuously in the system
3.7.4.3
maximum transient case pressure
maximum pressure peak that may be imposed by the hydraulic system on the pump case drain port
3.8
rated discharge flow
flow rate measured at the pump delivery port under conditions of:
 rated fluid temperature;
 rated inlet pressure;
 rated case drain pressure;
 maximum full-flow pressure;
 using the hydraulic fluid specified in the detail specification
Note 1 to entry: The flow shall be measured in the compressed state.
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ISO/DIS 8278
3.9
rated displacement
maximum theoretical volume of fluid generated by one revolution of the pump drive shaft at full stroke
Note 1 to entry: The rated displacement shall be calculated from the geometrical configuration of the pump, without
allowing for the effects of:
 permissible manufacturing tolerances;
 distortions of the motor structure;
 the compressibility of the hydraulic fluid;
 internal leakage;
 temperature.
The rated displacement is used to indicate the size of the pump rather than its performance.
3.10
rated speed
maximum speed at which the pump will operate
Note 1 to entry: The rated speed is expressed as a number of revolutions of the pump drive shaft per minute
3.11
response time
time interval between the moment when an increase (or decrease) of the pump delivery pressure begins and
the subsequent time when the delivery pressure reaches its first maximum (or minimum) value, when
connected to a specified circuit
3.12
stability
freedom from persistent or quasi-persistent oscillation or “hunting” of the pump (cyclic variations in speed) at
any frequency that can be traced to the delivery control mechanism, within stated limits in the detail
specification
3.13
pump overall efficiency
pump overall efficiency (including volumetric efficiency) is obtained from the equation:
pump overall efficiency (%) = (output fluid power/input shaft power) x 100
where:
 input shaft power = shaft torque x RPM;
 output fluid power = (full-flow pressure – inlet pressure) x rated flow.
Note 1 to entry: This equation ignores compressibility effects. If this equation is to be used, the flow rate measurement
should be made on the compressed flow stream.
3.14
rated endurance
total number of hours and cycles of operation to be included in the endurance phase of its qualification testing
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ISO/DIS 8278
3.15
first article inspection
FAI
process that conducts the following:
 verifies that the parts of a component complies 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;
 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 General requirements
4.1 Order of precedence
The detail specification shall take precedence in the case of a conflict between the requirements of this
standard and the detail specification.
4.2 Hydraulic system characteristics
The hydraulic pump shall be designed to supply the hydraulic system as defined in the detail specification.
The detail specification shall include the characteristics of the hydraulic system in which the pump is to be
used. This shall include the flow versus pressure curves for the inlet, discharge and case drain lines for the
following hydraulic fluid temperatures:
 normal operating temperature (for example + 20 °C);
 rated temperature;
 minimum continuous temperature.
4.3 Airworthiness requirements
The hydraulic pump shall comply with the applicable airworthiness requirements.
4.4 Qualification
Hydraulic pumps furnished under this standard shall be products that have passed the qualification tests
specified in the detail specification.
5 Functional requirements
5.1 Hydraulic fluid
The detail specification shall state the applicable hydraulic fluid.
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ISO/DIS 8278
5.2 Pump pressure
5.2.1 Rated discharge pressure
The design of the pump shall be such as to maintain rated discharge pressure at the following combination
and range of conditions:
 from 30 °C to rated temperature;
 from 50 % to 125 % of rated speed;
 at rated inlet pressure.
The value of the rated discharge pressure shall be stated in the detail specification and shall be one of the
following values of rated discharge pressure listed in Table 1 (derived from ISO 6771):
Table 1 — Rated Discharge 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

The maximum and minimum tolerance of the rated discharge pressure shall be specified in the detail
specification: The permissible tolerance range shall be doubled in each direction for fluid temperatures below
30 °C or pump speeds from 25 % to 50 % of rated speed.
5.2.2 Maximum full-flow pressure
The maximum full-flow pressure of the pump shall be defined as the maximum discharge pressure at which
the pump control will not be acting to reduce pump delivery at rated temperature, speed and inlet pressure.
The detail specification shall specify the minimum value of the maximum full-flow pressure (see Figure 1).
5.2.3 Pressure pulsations
The detail specification shall state the maximum permitted amplitude of the discharge pressure pulsations.
The amplitude of pressure pulsations shall be determined by the test procedure of 14.2.9.
5.2.4 Inlet pressure
5.2.4.1 General
The inlet pressure shall be measured at the inlet port of the pump in a manner that indicates the static head.
5.2.4.2 Rated inlet pressure
The detail specification shall state the value of rated inlet pressure, which shall be in kPa (or psi) absolute.
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ISO/DIS 8278
5.2.4.3 Minimum inlet pressure
The detail specification shall state:
 the value of the minimum inlet pressure, which shall be in kPa (or psi) absolute, and whether it applies
during a short term high flow condition or during a steady state failure case;
 the associated minimum hydraulic fluid temperature;
 any allowable performance degradation when the pump operating at the minimum inlet pressure.
The purchaser shall specify the inlet conditions that will exist at the pump inlet including the provision of the
circuit impedance for the pump inlet and discharge piping system and/or a complete physical description of
the circuit. This is to enable the supplier to conduct a dynamic flow analysis to determine the pump operation
at the minimum inlet pressure.
5.2.4.4 Maximum inlet pressure
The detail specification shall state the value of the maximum steady state inlet pressure, which shall be in kPa
(or psi) absolute.
5.3 Case drain pressure
5.3.1 Rated case drain pressure
The detail specification shall state the value of the rated case drain pressure for the pump case, which shall
be in kPa (or psi).
5.3.2 Maximum transient case drain pressure
The detail specification shall state the value, duration and frequency of occurrence of the maximum transient
case drain pressure for the pump case, which shall be in kPa (or psi).
5.3.3 Maximum case drain pressure
The detail specification shall state the value of the maximum case drain pressure for the pump case, which
shall be in kPa (or psi).
5.4 Flows
5.4.1 Pump rated discharge flow
The detail specification shall state the value of the rated pump discharge flow, which shall be in l/min (or gpm).
The minimum and maximum rated discharge flow shall be specified.
5.4.2 Pump case flow
The detail specification shall state that the pump shall be capable of producing at least a minimum case drain
flow to limit the differential temperature between the inlet port and the case drain port to a stated maximum
value.
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ISO/DIS 8278
The pump case flow rate (which shall be in l/min (or gpm)) shall be specified under the following conditions:
 rated discharge pressure (minimum attainable steady-state flow);
 rated temperature;
 any discharge flow demand between 5 % to 100 % of rated flow;
 a given maximum differential pressure between case pressure and inlet pressure.
The minimum and maximum case drain flow shall be stated at conditions specified in the detail specification.
If the case drain flow is routed to a system heat exchanger, the detail specification shall state the minimum
case flow.
5.4.3 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:
 the pump filled with fluid, but un-pressurized;
 when subject to proof pressure at ambient temperature;
 when the pump is supplying rated discharge flow.
b) Qualification testing:
 over the expanded test envelope;
 at the completion of the endurance test;
 when subject to proof pressure at rated temperature;
 when subject to burst pressure at rated temperature.
5.4.4 External leakage
No leakage sufficient to form a drop from the pump case or from any case static seal shall be permitted.
Dynamic shaft seal leakage shall not be considered as external leakage.
5.5 Speed and direction of rotation
5.5.1 Speed
5.5.1.1 Rated speed
The rated speed of the pump shall be defined as the maximum speed at which the detail specification requires
the pump to operate continuously at rated temperature and at rated discharge pressure. The rated speed shall
be expressed as a number of revolutions of the pump driving shaft per minute.
The rated speed of the pump shall be stated in the detail specification.
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ISO/DIS 8278
NOTE As an indication, the maximum recommended values are given in the Nomograph in:
 Figures 2a and 2b for commercial aircraft applications;
 Figures 3a and 3b for military aircraft applications.
If speeds are kept well below those indicated by the curves, the operating life may be improved. However, several system
factors such as fluid, temperature, duty cycle, contamination, expected life, etc. will also influence the values.
5.5.1.2 Overspeed
Unless otherwise specified in the detail specification, the pump shall be capable of operation at 115 % of rated
pump discharge flow for the durations and at the conditions of Table 7.
5.5.2 Direction of rotation
The direction of rotation of the pump drive shall be stated in the detail specification, and shall be clearly
indicated on the installation drawings and by a label on the pump.
5.6 Torque
The detail specification shall specify:
 the maximum value of driving torque for rated operating conditions for the pump;
 the torque value when the pump is operated at zero flow, at rated pressure, temperature and rotation
speed.
5.7 Pump Overall Efficiency
The following efficiency values shall be stated in the detail specification:
 the overall efficiency of the pump when new;
 the overall efficiency of the pump after endurance test, this value being considered as an objective.
When determining output power by calculation from flow rate and pressure change, only the net pressure
difference between inlet and outlet ports of the pump shall be used. The flow rate may be as measured in the
low pressure side of the discharge line, provided that adequate compensation is made for compressibility
when calculating efficiency.

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ISO/DIS 8278

Key
X pump speed in rpm x 1 000
Y rated displacement in millilitres per revolution
a recommended maximum rated speeds
Figure 2a — Nomograph of maximum recommended values for rated speeds against pump
displacement (Metric units) — commercial aircraft applications
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ISO/DIS 8278

Key
X pump speed in rpm x 1 000
Y rated displacement in cubic inches per revolution
a recommended maximum rated speeds
Figure 2b — Nomograph of maximum recommended values for rated speeds against pump
displacement (American units) — commercial aircraft applications
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ISO/DIS 8278

Key
X pump speed in rpm x 1 000
Y rated displacement in millilitres per revolution
a recommended maximum rated speeds
Figure 3a — Nomograph of maximum recommended values for rated speeds against pump
displacement (Metric units) — military aircraft applications
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ISO/DIS 8278

Key
X pump speed in rpm x 1 000
Y rated displacement in cubic inches per revolution
a recommended maximum rated speeds
Figure 3b — Nomograph of maximum recommended values for rated speeds against pump
displacement (American units) — military aircraft applications
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ISO/DIS 8278
5.8 Variable delivery control
5.8.1 General
All pump models shall incorporate means to control the delivery which shall act to increase the delivery of the
pump from zero to its maximum full-flow value for any given operating speed, as the discharge pressure is
reduced from rated discharge pressure to maximum full-flow pressure and vice versa.
5.8.2 Adjustment
Means shall be provided to adjust the delivery control mechanism to cause zero flow to occur at rated
discharge pressure. This adjustment shall, preferably, be continuous or it is acceptable for it to be in steps of
less than 1 % of the rated discharge pressure over a minimum range from 95 % to 105 % of the rated
discharge pressure.
The adjustment device shall be capable of being securely locked and it shall be possible to carry out
adjustment and locking using only standard hand tools. Where practicable, the adjustment device shall be
fitted in such a way that adjustments can be made while operating under full system pressure with negligible
loss of fluid.
5.8.3 Response time
The real-time plot of discharge pressure against time shall be used as the criterion of movement of the
discharge control mechanism. All pumps shall have a maximum response time in accordance with the detail
specification when changing the flow demand, unless otherwise specified in the detail specification when:
a) operating at rated inlet temperature;
b) at rated flow;
c) in a circuit, with the system impedance defined in 14.2.8.2.2.
In Figures 4 and 5, the time intervals t and t are the response times of the pump as a function of the system
1 2
impedance.
The pump discharge pressure must be stabilized within ±2 % of the rate
...