The present invention is concerned in particular with the scheduling of maintenance actions such as washing events for a compressor of a gas turbine. An objective function including fuel/power price forecasts is evaluated/optimised in order to determine the advisability of a washing event. The cost function depends on a state vector comprising both Integer/Boolean and continuous state variables which are interconnected via a set of rules or constraints. Mixed Integer Programming (MIP) is a used for implementing the inventive procedure
