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Aerospace Topic: Hydraulic Fluids in Aviation

  1. May 22, 2016 #1

    We all know that, in Commercial aviation, we use Hyjet (SKydrol or 500B4). and in military we use MIL-H-83282 (red oil). what are the main reasons?

    MIL-H-83282 has a synthetic hydro carbon base and contains additives to provide the required viscosity and anti wear characteristics, which inhibits oxidation and corrosion. and having a temperature range of -40 Deg C to +135 Deg C, and its a fire resistant fluid.

    Why are we not using MIL standard fluid for Commercial aircraft?
    What are the defined standards for Hydraulic systems in Commercial and Military? (where can i get that info. CS/FAA-25?)
    Difference in Properties of both fluids?

    Thanks in Advance.
  2. jcsd
  3. May 22, 2016 #2


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    There are many different standards. You must use the approved fluid. How could you know that two fluids specified in different standards were not the same ?
    Anything MIL spec wil be more expensive because the taxpayer pays the bill.
    Commercial airlines probably get exactly the same fluid for a lower price, but with a different standard and part number.


  4. May 22, 2016 #3
    Thanks for the reply. Actually, the two specified fluids are not the same. I'm working in this area currently. we use red oil for military and hyjet for commercial. Both have different properties, i think. While we handle those fluids, we use different set of gloves for each type and different care. Thanks for the manual info book. i'll dig into that and observe the differences and post back the reasons.
  5. Jul 7, 2016 #4
    The reason why Hyjet is used in commercial sector is because of its inflammable properties upto 1600 C. and its auto ignition point is about 400 0 C. While Red Oil or MIL-5606/83282 has a lower flash point of about 940 C. They use red oil in military sector because of the confidentiality in technologies and gathering information.
  6. Jul 8, 2016 #5


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