Aerospace Hydraulic Systems

Research and field experience has established that fluid contamination degrades the performance and life of hydraulic equipment.

To improve hydraulic component and system reliability and performance, fine filtration is required. For details on filtration solutions for hydraulic systems, contact your local Pall sales representative at

  Aerospace, Defense, and Marine OverviewAerospace ProductsApplications
Air Systems
CBRN Protection
Cabin Air
Engine Protection - Helicopters
Engine Protection - Vehicles
Other Air Systems
Fluid Recycling
Fuel Systems
Hydraulic Systems
Lubrication Systems
Water Treatment/Desalination

Problems Caused by Contamination

The hydraulic fluid is a repository for particulate contamination. This contamination originates from several sources:
  • Debris built-in during all the processes involved in the manufacture of the hydraulic system and its components
  • Wear debris generated during hydraulic system operation
  • Environmental contamination ingressed during normal operation or added during routine servicing and maintenance
If this contamination is not removed it will recirculate around the fluid system and cause the following problems:

Component wear, eg abrasive wear on pumps. Increased pump leakage, higher temperatures, lower pump pressures and reduced efficiency
Valve Erosion and stiction Jerky valve movement, valve hysteresis, valve jamming
Water Contamination Corrosion, high acid levels in hydraulic fluid
Water Contamination and High Temperature Fluid Oxidation leading to degradation in hydraulic fluid properties

More details on mechanisms of wear.

Benefits of Fine Filtration

Fine filtration removes harmful contaminants from the hydraulic system and this will:
  • Improve the operating reliability and performance of the hydraulic system
  • Significantly reduce maintenance costs
  • Extend component service life

Typical Filter Locations – Hydraulic System

  • Pressure line filter
    • Protects system from pump generated contaminant
    • Generally requires high collapse pressure elements
  • Return line filter
    • Removes contaminant ingressed or generated by valves and actuators
    • Prevents contaminant from returning to reservoir and pump
  • Case drain line filter
    • Removes pump wear particles before they go to other parts of system
Last Chance Filters (LCFs) upstream of critical or sensitive components

  • Ground support equipment (GSE) – Portable Purifier
    • Removes solid particulate contaminant using a high efficiency filter element
    • Removes water, air and volatile solvents using a vacuum dehydration process

Schematic diagram of typical hydraulic system

Filter Solutions

Filtration products include:
  • Filter Manifold
  • Filter Assembly
  • Filter Element
  • Differential Pressure Indicators/Switches
  • ARB Valve
  • Bypass valves/Check Valves.
  • Last Chance Filters
  • Portable Fluid Purifier
To determine the best product for your application, contact your local Pall sales representative at

Technical Papers/Field Studies

Bensch, L (2005) "Contamination Control in Hydraulic and Lubricating Systems"

Bensch, L. Lundquist, J. (1999) "The Impact of New Test Dusts on Measuring and Maintaining Aircraft Hydraulic Fluid Cleanliness"

Bensch, L. Needleman, W. Lundquist, J. (1996) "Improving Commercial Airliner Hydraulic System Reliability through Contamination Control" Presented to the FAA Hydraulics Task Force, SAE A-6 Committee, USA

Madhavan, P. Bensch, L. Xiaojian, T. (2008) Pall Corporation and Southwest Research Institute, U.S.A. "Advances in Laboratory Performance Evaluation of Hydraulic Filter Elements – Application to the Study of Aircraft Hydraulic Filter Elements" 16th International Colloquium TribologyTechnische Akademie Esslingen

Madhavan, P (1996) "Service Life Extension of Hydraulic and Lubricant Fluids Through Contamination Control" First Annual Joint Service Pollution Prevention Conference and Exhibition, USA

Madhavan, P (1999) "Extending the Service Life of Hydraulic and Lubrication Fluids via Contamination Control"