 The Arrow 's thin wing required aviation 's first 4 @,@ 000 lb / in2 ( 28 MPa ) hydraulic system to supply enough force to the control surfaces , while using small actuators and piping . A rudimentary fly @-@ by @-@ wire system was employed , in which the pilot 's input was detected by a series of pressure @-@ sensitive transducers in the stick , and their signal was sent to an electronic control servo that operated the valves in the hydraulic system to move the various flight controls . This resulted in a lack of control feel ; because the control stick input was not mechanically connected to the hydraulic system , the variations in back @-@ pressure from the flight control surfaces that would normally be felt by the pilot could no longer be transmitted back into the stick . To re @-@ create a sense of feel , the same electronic control box rapidly responded to the hydraulic back @-@ pressure fluctuations and triggered actuators in the stick , making it move slightly ; this system , called " artificial feel " , was also a first . 
