Prediction of Susceptibility of Small Aircraft to Pilot-Induced Oscillations

Indirect (Fly-By-Wire) flight control system for small aircraft has been developed at Department of Avionics and Control, Rzeszow University of Technology since 2000. Experimental SPS-1/A has been designed as an intuitive, human centered, simplified software-based flight control system. It would allow pilots with limited aviation experience to establish a safe control of the aircraft. Operator of the system is fully supported in normal control mode and all the properties of SPS-1/A are employed then. Second mode (simple CAS, Control Augmentation System) is reserved for more experienced operators for “more manual flying”. Third level of control should be used in emergency only, flight control computers are bypassed and control surfaces are deflected directly then. The system was tested on the board of PZL-110 “Koliber” aircraft in 2003 and next in 2006. First run of in-flight tests was preceded by detailed analysis of possibility of pilot-induced oscillations (PIO) occurrence. At first analytical PIO criteria were applied to the dynamics of experimental aircraft equipped with SPS-1/A. Next indirect flight control system was evaluated during pilot-in-the loop simulations and susceptibility to PIO was rated by pilots. PIO detector was applied for analysis of data collected during ground simulations as well as for data recorded during in-flight tests. Results of analytical criteria, simulations and flight experiments have been presented and discussed in this work.