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In 1948, Douglas Aircraft Company and Monsanto cooperatively developed Skydrol 7000, the first phosphate ester fire resistant hydraulic fluid to address the growing number of aircraft hydraulic fluid fires.
With advancements in aircraft designs, improved hydraulic fluid performance was needed. Airframe manufactures' specifications defined these performance enhancements via Type I, II, III and IV designations.
Since 1977, Skydrol LD-4 and 500B-4 have met the performance demands of commercial aircraft.
Skydrol 5, introduced in 1996, was the first Type V fluid approved under BMS3-11. It still offers the lowest density of any phosphate ester fluid, plus better paint compatibility and thermal stability compared to Type IV fluids.
Skydrol PE-5, our newest Type V fluid, is approved by both Boeing and Airbus, and compatible with all aircraft using phosphate ester fluids. It offers the longest fluid life of any phosphate ester fluid, plus improvements over Type IV fluids in density and low temperature viscosity.
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Skydrol Chronology
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Type
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Name
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Industry Need
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Introduced
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Discontinued
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--
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Skydrol 7000
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Fire Resistance
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1948
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1972
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I
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Skydrol 500A
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Low Temp Viscosity
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1957
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1969
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II
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Skydrol 500B
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Erosion Resistance
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1968
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1981
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III
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Skydrol LD
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Thermal Stability
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1970
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1981
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IV
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500B-4
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Erosion Resistance & Thermal Stability
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1977
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Current
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IV/V
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Skydrol LD-4
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Erosion Resistance & Thermal Stability
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1977
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Current
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IV/V
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Skydrol 5
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Low Density, High Temperature Stability
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1996
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Current
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V
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Skydrol PE-5
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Harmonized Specification
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2010
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Current
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