This paper presents procedures for designing controllers for complex dynamical systems using single- and multiinput modal control theory. It is shown that the design of the appropriate modal controller for a given system is greatly facilitated by the inspection of mode-controllability indices which constitute the mode-controllability matrix of the system. The design procedures enable controllers for multi-input systems to be synthesized by sequential applications of a single-input theory or by an alternative method in which it is possible to impose gain constraints on the modal controller. The power of these procedures is demonstrated by the design of both longitudinal and lateral controllers for the Sikorsky SH-3D Sea King helicopter.