The fluidized catalytic cracker unit (FCCU) process provides an involved, coupled and nonlinear multivariable control problem. A systematically constructed chain of gain-scheduled fuzzy logic controllers (GS-FLCs) is used with some generalisable modifications. A single fixed 'full' fuzzy rule-base is sufficient to sustain performance for each control channel. The key FLC modification is the use of a sigmoidal gain-schedule (SGS) that is the significantly parameter-reduced equivalent of a flexible fuzzy input/output variable. The SGS simultaneously has a crisp and intuitive gain-like format, and together these permit relatively simple heuristic tuning for the GS-FLC. This nonlinear GS-FLC structure permits the use of a very simple static linear decoupler (SLD). The general multivariable GS-FLC/SLD construct demonstrates very good controller performance, covering servo/regulatory and robustness tests.