The technical note introduces a constrained optimization approach to active fault detection and control. Detection and control aims can be expressed either as a part of an objective function or as a constraint. Five principal formulations of active fault detection and control problem are proposed and investigated in the technical note. Three formulations are focused on alternative detection and control aims combinations while the other formulations represent marginal cases that outline a relationship to the well know fields of optimal control and active fault detection. The underlying difficulty of the optimal solution is discussed and a suboptimal solution is proposed that makes use of nonlinear programming techniques.