Working liquid NGZH-4u is synthetic flame safety a liquid on the basis of aethers of phosphoric acid. It has been created liquid NGZH-4 in exchange earlier widely applied in aircraft calling erosion of valves of hydrosystems and, as consequence of it, liquid leak. Liquid NGZH-4u is erosion-resistant liquid, contains the additives improving it вязкостные, antierosive, antioxidizing properties. It is efficient in the range of temperatures from -55 to 125 °C at working pressure to 21 megapascal. Has temperature of spontaneous ignition 650-670 °С, slowly burns in a flame, but does not sustain combustion and does not extend a flame unlike oil liquids of type АМГ-10. Is good softener and solvent for many nonmetallic materials, therefore at use of the last in contact to liquid NGZH-4u it is necessary to check carefully their compatibility or to use only those materials which are picked specially up and recommended for liquids of type NGZH.