Research On Large Aircraft Modeling,hazards Detection And Control Under Low-level Windshear

Low-level windshear is a serious threat to flight operation. However, the windshear flight test conditions is difficult to implement and the windshear flight test itself is quite dangerous. In this paper, the full flight envelope 6-DOF large aircraft model flying through the low-level windshear is established to supply a platform for windshear detection research and windshear penetrating control law design. The aircraft model contains aircraft dynamics, flight environment and aircraft system model; The flight environment supplies windshear model, atmosphere data and terrain data and the aircraft systems include sensors such as ADC and IRS, engine, landing gear and actuators.The current algorithms take real time wind velocities to detect low-level windshear without consideration of real time altitude, weight and remaining thrust. Thus the warning is fast enough with low remaining thrust and low altitude. In this paper, the altitude, weight and remaining thrust supplied by Flight Management System are used to modify current low-level windshear algorithm and the Mont-Caro simulation experiment is taken to determine unfixed parameter in the modified detection algorithm. The experiment result shows that the new method can reduce false alarms efficiently. The Mode 7 function of Terrain Awareness and Warning System (TAWS) uses real-time airspeed, angle of attack, radio altitude and other information to detect the presence of low-level windshear. This function will warn the pilot to avoid dangerous situation which will lead to controlled flight into terrain (CFIT) caused by wind shear. The onboard verification conditions for TAWS Mode 7 function is very difficult to achieved, so a simulation and verification platform was developed to establish verification conditions for an engineering prototype TAWS. This platform uses low-level windshear model and 6DOF aircraft model togenerate the data required by TAWS to detect wind shear. A flight scene database is established to simulate the scenarios for many times and whether the caution and warning alerts will be given correctly when flying though an windshear is then verified.Traditional aircraft auto landing method is to use ILS to detection the deviation angle from glide slope and auto-pilot is used to eliminate deviation by pitch angle control. As the New Navigation System developed a lot recently, the auto approach and landing with GNSS became more practical. In this paper, the mathematical model and real time simulation system for auto approach with GNSS when encountering low-level windshear is established. The pilot need to be more careful and need to maintain flight path when encountering caution level windshear. In this paper, Linear Quadratic Tracker(LQT) is used to design an autopilot for auto approaching with windshear instead of pilot manual operation and the robustness of this controller is researched then. The flight model is nonlinear with velocity sharply variation, thus the Gain of LQT are scheduled with Airspeed to settle this problem. The simulation indicates that the Gain Scheduled LQT is quite helpful in maintaining flight path with low-level windshear disturbance.