Fire-resistant hydraulic fluids have proven their ability to provide safe, reliable and economic operation in the commercial subsonic airline fleet. These operational criteria will become even more critical in the supersonic transport (SST), and additional demands will be made upon the hydraulic fluid. This paper will describe the development of a new fire-resistant hydraulic fluid specifically designed for the SST.
A satisfactory aircraft hydraulic fluid must meet many criteria, including fire resistance. All presently available classes of hydraulic fluids were reviewed in terms of such parameters. Because of the deficiencies revealed in this analysis, it was necessary to undertake a basic research program to develop new fluids. This program is discussed in general terms and the end products, fire-resistant polyaryl fluids, are described in detail. Physical, chemical, and performance properties are included.
Thus, a completely new class of fire-resistant hydraulic fluids has been established. A formulation has been developed around the specific requirements of the SST and is available for further evaluation by all concerned.