The Study On Ground Reaction Force Of Civil Aircraft Wheels Up Landing

The aircraft landing can be divided into two ways according to the landing status: the normal landing and the emergency landing.Aircraft wheels up landing is the controlled flight emergency landing under the condition that the aircraft undercarriage could not open.The ground reaction force gained from the collision with the ground for the reason that the undercarriage can't work well.The calculation and analysis of the ground reaction force is an essential part of the crashworthy airworthiness requirements as it is important in the aircraft structure design and system design.So far,there is no unified method for the civil aircraft's ground reaction force analysis.The methods adopted by the different aircraft manufacturers are quite varied,and even the same manufacturer will take the different methods for the calculations of different models of aircrafts.This paper is based on a type of aircraft,studying the method of solving the ground reaction force of civil aircraft.Take the method of combing the simplified fuselage with the equivalent spring model to solve the ground reaction force of civil aircraft's wheels up landing.Study the ground reaction force under the different conditions of the landing gears open/closed.The main research contents are as follows:1.Confirm the touchdown location and simplification of model.Firstly,the touchdown position under the aircraft wheels up landing of different configurations is determined by the rigid-body kinematics and the corresponding simplified models(belly and nacelle)and fuselage are based on the stiffness equivalence.This paper calculated the ground reaction force by the combination of simplified model,compared with the NASA test report and verified the effectiveness and correctness of the local simplify model.2.The nonlinear relationship between deformation and force is determined.The local simplified models are calculated by connecting it to the rigid fuselage respectively.The fuselage and nacelle local models' nonlinear relationships between force and deformation are gained by the emergency landing simulation under the airworthiness specified safety pitching angle.3.The calculation of the ground reaction force.The relationships between force and deformation of undercarriage,belly and nacelle are described by the spring elements.The ground reaction force is calculated and analyzed by simulating the process of the aircraft landing under the condition of the undercarriage different open/close combination.The feasibility and accuracy of the method is verified by comparing the calculated results with the NASA experiment results.