HYDRAULIC fluids for high-speed, high-altitude aircraft need to encompass the temperature range -65 F to 450 F and over. In addition, the other physical properties must be satisfactory.
Since none of the fluids now being used in hydraulic systems are completely satisfactory, the Air Force has instituted a research program designed to develop a fluid that is capable of meeting these severe requirements.
Of the fluids investigated, the silicates and the polysiloxanes are considered to have real possibilities, although both need further development work done on them to take care of certain deficiencies.