The aircraft complex systems (ACS) contains the auxiliary power unit (APU) based gas turbine, the performance assessment is totally cramped to inspection of different kind of parameters. So many other parameters can be observed in Quick Access Recorder (QAR) returns the APU condition from different aspects not having enough attention. The investigation intends to propose incorporated performance indicators by feature extraction many observing parameters. To approve the effectiveness of the strategy by anomaly identification, the clustering analysis is conducted. This technique can possibly effectively evaluate performance of some complex aircraft systems for early cautioning and prevent degradation at early stage. The parameters of Rowen's model for APU based gas turbines in unique studies are assessed by utilization of accessible operational and performance data. Here, the work is planned to make understanding into different parts of the APU model and to present simple and comprehensive strategy to extract the parameters out of basic physical laws, focusing especially on researchers to let their interest in dynamic models and simulations. Gas turbine parameters are approximated by using straightforward thermodynamic assumptions, resulting great performance. In this paper, the step response of the simulation model is also simulated for number of scenarios and is presented here.