Early aviation hydraulic systems were used to apply brake pressure. These systems used a vegetable oil-based hydraulic fluid. As aircraft design produced larger and faster aircraft, greater use of hydraulics was necessary.
These advances led to development of petroleum-based hydraulic fluids such as-O-3580 and, later, Mil-H-5606. Shortly after World War II, the growing number of aircraft hydraulic fluid fires drew the collective concern of the commercial aviation industry and the public.
In 1948, Monsanto Company, Solutia’s former parent, worked with Douglas Aircraft Company to develop a fire-resistant hydraulic fluid based on phosphate ester chemistry, which was named Skydrol® 7000. As the transport industry moved toward jets, Skydrol® 500A fluid was developed to meet the environmental needs of the new aircraft, and with the continuous development of more advanced aircraft further modifications to Skydrol fluid formulations were made.
These changes, required by the aircraft manufacturers, are known as modifications to the fluid specification ... or simply as Type I, II, III, IV, and now Type V fluids. Skydrol® LD-4 and Skydrol® 500B-4 hydraulic fluids are Type IV fluids formulated to exceed the rigid specifications of the aircraft manufacturers. They have been in commercial usage since 1978 and have demonstrated outstanding performance. Skydrol 5 was our first Type V fluid, and now Skydrol PE-5, introduced in 2010, is our newest, longest lasting hydraulic fluid. In 1997, Solutia Inc. was formed from the Industrial Chemicals Division of Monsanto.
Eastman Chemical acquired Solutia and the Skydrol product line in 2012. Skydrol became part of the Eastman Aviation Solutions family of brands in 2014 combining the proven performance of Skydrol with SkyKleen and Eastman Turbo Oils to provide an industry leading fluids solution to the industry.