Solenoid-operated hydraulic valves for aircraft applications

DURING the past several years there has been a definite trend by some aircraft manufacturers to eliminate hydraulic controls from combat airplanes. The vulnerability of hydraulic systems used on airplanes manufactured during this period and to a certain extent today are big factors in promoting this trend. Space requirements in the cockpit of an airplane to mount control valves and accommodate necessary piping to these valves, difficulty with packings at extremely cold temperatures, and the lack of flexibility of the control system are other factors that contributed to the aforementioned trend.