Study On The Analysis Method Of Flight Control System Failure Effect

The performance of flight control system affects the flight capability of the aircraft directly.In the airworthiness certification,the system safety analysis in failure condition and the flight test verification in failure condition are the critical and difficult point in airworthiness certification.For existing failure effect analysis,subjective experience is often used to determine the effect level of the aircraft flight control system failure,but as a result of actual pilot control differences,environment,engineer experience differences and other factors,the assessed failure effect level may be different from the reality.And it is a trend to evaluate the effect of system failure by numerical simulation.In this paper,by developing the pilot-aircraft closed-loop simulation model,the analyze method of flight control system failure effect was studied,and it mainly includes:First of all,a pilot-aircraft-environment system simulation model is developed based on aircraft motion and kinetic model.It includes the pilot model,flight control system model,environment model and non-linear 6 degree-of-freedom aircraft model.And the longitude and lateral control system are designed separately using perturbation method.McRuer Pilot Model is used to simulate the pilot manipulation in the closed loop,in which the time delay of pilot's reaction to the failure,and the randomness of pilot's manipulation were considered.And the continuous turbulence is considered in the environment model.Secondly,according to the requirements of airworthiness regulation,with the typical flight control system architecture as the object,the main failure modes of flight control system were analyzed and the modeling of jamming and oscillation was carried out.Thirdly,for flight risk after flight control system failure,a risk level classification method of flight safety is proposed according to FHA,which dividing the risk level into four level including no-effect,minor,serious,and disastrous.The basic of risk level dividing is the limitation of critical parameter.This method can assist in the process of FHA in safety analysis.Finally,aiming at flight control system failure flight test,a risk probability calculation method is put forward,which can assess the flight test risk by the risk probability values,and give risk mitigation measures according to the results of sensitivity analysis.An assessment method of flight control system failure is put forward in this paper,which can be conducted in the early design,assist to determine the effect level of failure in FHA process,and provide references to flight test risk assessment.