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New Concept of High Pressure Hydraulic Filter for Aeronautics Preserving Environment

European Union
Complete with results
Geo-spatial type
Project Acronym
STRIA Roadmaps
Vehicle design and manufacturing (VDM)
Transport mode
Airborne icon
Transport policies
Environmental/Emissions aspects
Transport sectors
Passenger transport,
Freight transport


Background & Policy context

In Aeronautics, hydraulics energy is currently used for brakes, engine reverse system and flaps command. To significantly reduce weight, the major changes in the future will be: either an increase in the hydraulics pressure from 3000 Psi to 5000 Psi; or, an hybrid architecture electrical / hydraulics known as the EHA concept (Electrical Hydraulics Actuator), envisaged with possible increase of hydraulics pressure. For large aircrafts, the increase of pressure is studied in details and is planned in the future aircrafts. In parallel, the EHA concept may be used either in redundancy or complementary. For middle range aircraft, the EHA concept is nowadays preferred but the increase of pressure may be used in the future. The high-pressure technology is already applied in middle range military aircraft, and its civil application appears promising, stanting with the A380. In both cases, one of the key elements of the hydraulics circuit is the filtration function. Today most hydraulics filtration systems use renewable cartridges that are thrown away after use without the possibility of the incinerability or recycling. It is a highly polluting process, bearing in mind that hydraulics fluids are very chemically aggressive and hazardous to human health.

This project consists of working on future filtration requirements : use of more ecological material, improvement of cartridge lifetime and an increase in working pressure. The proposed approach is firstly to understand the physical mechanism of filtration by simulation. Theoretical models are proposed and then compared with experiments to obtain a high degree of confidence. New materials are studied, adapted and tested to fulfil performance requirements, most particularly incinerable conditions. Manufacturing processes are investigated for availability, cost impact and environmental constraints, and finally mock-ups are manufactured and tested to validate the technologies.


The research objectives of the AEROFIL project related to:

  • fluid mechanics of porous media modelling and characterisation of filtration system with very high pressure (up to software development and validation);
  • ester Phosphate characteristics for High pressure;
  • synthetic media with an increase in autonomy;
  • composite or polymer elements characteristics;
  • polymer meshes characteristics

The project was expected to produce the following deliverables:

  1. ester Phosphate characteristics vs Pressure and temperature;
  2. precise definition of a filtration system compatible with very high pressure hydraulic systems, increasing lifetime by a factor of 2 and incinerable;
  3. for this filtration system:
    • mechanical design software
    • fluid dynamics simulation software
    • mock ups
    • economical and environmental Life cycle analysis

The work on the project encompassed the following tasks:

Task 1: Needs and Concept description

The goal of this task is to define the requirements for the filter and the resulting requirements on the different components. It also includes the choice of a reference equipment for comparison between former and new technologies

Task 2: Material and technology

It consists in research and development work in new material needed for the conception and the manufacturing of the different components included in the filters in order to fulfil the Scientific and technological objectives of the project.

Task 3: Simulation
This task covers all activities to develop a numerical tool for simulation of flow across the filter. It includes all activities related to the modelisation of the flow and of particles deposition during contamination process, and afterwards, actual development of the sofware and validation by comparison with real data.

Task 4: Simulation tool validation on existing filter technologies

Task 5: Filter mock-up

Activities related to the design, procurement and manufacturing of a filter element prototype using the new technologies.

Task 6: Experimental testing
Testing of the filter element performances on a test bench and comparison between the former and new technologies

Task 7: Simulation tool refinement based on new technologies testing

Comparison of numerical results with test results, and refinement of numerical data


Parent Programmes
Institution Type
Public institution
Institution Name
European Commission, Directorate-General for Research (DG Research)
Type of funding
Public (EU)


The main results of the project are concerned with:

  1. Optimized manufacturing of carbon composite grid tubes

    • For efficiently manufacturing grid tubes using filament winding the process parameters have to be tuned carefully. As a result, tubes can be produced which have excellent mechanical properties at an extremely low weight.
  2. Multi-layers synthetic fine fibre filter media for hydraulic oil filtration
    • The project results have shown the capability to design new filter media able to meet the high particles removal efficiency and long service life required by the new aircraft hydraulic system.
  3. Design Tool for pressurized tube with hole
    • Software capable of calculating the buckling pressure of a holed tube subjected to internal and/or external pressure. Production of design plots for thickness radius and length.
  4. Evaluation of the resistance of composite materials in an aggressive environment
    • Techniques to evaluate the environmental resistance of polymer and polymeric composites;
    • Selection of thermoplastics and thermosets compatible with hot ester phosphate fluids.
  5. Life Cycle Analysis of Aeronautic Filters
    • Guidelines to calculate the effects of the use of an aeronautic composite filter on the environment and its global energy consumption
    • Evaluation of economical aspects
  6. Software design package for use with viscous fluids
    • A tool to assist engineers in assessing the design and performance of cartridge filters
  7. Fluid properties
    • Identification of Rheological and thermodynamical characteristics of hydraulic fluids used in commercial Aeronautics (ester phosphate bases) versus temperature (-60 ; +130°C) and pressure (up to 400 bars)
  8. Conception and realisation of specific laboratory equipment for fluid characterisation
    • Fall cylinder viscosimeter (patent), isotherm bulk modulus apparatus, Thermostated bath and hydraulic benches for pressurisation, enthalpimetric high pressure cell.
  9. Incinerable filtration system for different application (hydraulics, lube, Fuel…)
  10. Assembling processes for filters;
    • Optimised Glue composition and gluing process;
    • Surface treatment for plastic / fibrous materials gluing;
    • Welding process for plastic.

Technical Implications

Existing filter element for liquid aerospace applications are manufactured with fibre glass, Aluminium and Stainless steel. Technologies have been developed and validated for the design and the manufacturing of filter element 100% burnable. All components have been redesigned and material have been replaced by synthetic media, plastic and composite material.

These technologies are compatible with aeronautics fluids (kerosene, lubricants and hydraulics) and with temperature of circuits. They bring major interests and especially:

  • Mass reduction in between 30% to 70% depending on the application
  • Lifetime increase (between 30 to 100%)
  • Significant reduction of environment impacts either due to manufacturing of the component and also due to mass reduction in the aircraft

Policy implications

None - please see 'technical implications'.


Lead Organisation
EU Contribution
Partner Organisations
EU Contribution


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