The development of the F-16 flight control system (FCS) had definite impacts on the design of the primary control surface actuation devices. The YF-16 employed one of the first aircraft fly-by-wire (FBW) control systems. One of the challenges of the YF-16 FCS design was to use existing state-of-the-art components with little or no development required yet provide the necessary redundancy and reliability levels needed for a fly-by-wire system.The FSD and production F-16 programs allowed for the development of an integrated servoactuator (ISA) for use on the primary control surfaces. This ISA design combined the command servo and power actuator functions and allowed all types of actuator inputs to be summed electrically.The AFTI/F-16 airplane presented some unique requirements due to the implementation of a digital FBW system. Twin vertical canards meant additional actuation requirements.