Aircraft Modeling for Upset Recovery and its Applications - Development of a tool chain from model generations to flight simulations

Kurzfassung

Aircraft departing from the nominal flight envelop and entering upset situations have become a major safety concern for the air transportation industry. Evidence shows that purely relying on pilots to conduct the recovery maneuvers may not be an effective approach, thus more advanced alternative solutions are required. This report includes reviews of previous works and findings in the field of aircraft upset recovery. Starting from the current status of upset prevention approaches, detailed descriptions are given for various extended flight dynamics modeling methods formerly developed using wind-tunnel measurements and computational fluid dynamics simulations. Earlier attempts on implementing the extended model into flight simulator training programs, and control system designs for upset recovery are also examined. It is discovered that all researches in this field are essentially in their beginning stage with only premature solutions offered. Lack of common standards for evaluation of results can also be observed among various reference materials. Throughout the course of this master’s project, a complete tool chain is developed for generating extended and enhanced flight models for low speed flights. Starting from geometric based automatic generation of the baseline model, mathematical algorithms are added to supplement the model for simulation of aircraft dynamics in near stall and post-stall regions using decambering theories, as well as dynamic stall and spin dynamics modelings. Together with additional functions of empirical corrections, drag estimations and weight calculations, significant enhancement was made to computational capability of the German Aerospace Center’s in-house designed vortex lattice method program. The model is validated based on various reference materials. Direct comparisons to some wind-tunnel measurements, manufacturer’s reports and other academic publishing indicate satisfactory modeling results for the lift, drag, moments and control surface effectiveness. Furthermore, the simulation results of the Fokker 100 aircraft model are directly compared to flight data recordings of five different accidents involving aircraft upsets. Promising results are obtained for upset types of over-banking, rudder hard-over, symmetric stall and asymmetric stall spin. The model is designed to be applied into applications of both fields of integrated aircraft design and upset recovery control action researches. Concerning this project, the implementation of the model into German Aerospace Center’s Robot Motion Simulator aims at enabling realistic simulations of upset motions unachievable by conventional hex-pod simulators. Due to hardware constrains, simulation of flight upset with the current setup is not possible; however, analyzing the preliminary software simulation results demonstrate that with minor modifications, the Robot Motion Simulator is very capable of reproducing the motions created by flight upsets. Furthermore, a preliminary research is conducted into the evaluations of upset recovery control actions based on the observations of various simulations using the extended model.