Key words: aircraft, water surface, mathematical modeling, forced landing, forced landing on water, finite element model, dynamic strength, anti-crash model test, stress distribution, pressure distribution in the middle of fuselage.
Aircraft used offshore/across the sea must evaluate the performance of landing on water. At present, the anti-crash standards, design methods and analysis methods of aircraft usually only consider hard landing, and rarely consider landing on water. This is because landing on water involves multiple coupling fields, and the problem is very complicated. In order to simplify the problem, the finite element model of the whole machine is established by decoupling method, combining simulation with experiment, and using MSC.PATRAN/DYTRAN software platform. Including full-scale fuselage, wing and tail structure, and introducing specific parameters, the dynamic numerical simulation calculation of 13 working condition is carried out, the transient stress distribution of the structure during the impact of the aircraft on the water surface is predicted, and the strength analysis of the lower skin of the aircraft fuselage is carried out. The results show that the aircraft skin will not be damaged during the impact.
Aircraft and helicopters are used more and more frequently in offshore or cross-sea areas, and forced landing and water crash accidents are also increasing. Therefore, the civil aviation departments of all countries regard the safety of forced landing on water as one of the key inspection contents of issuing airworthiness certificates, and the laws and regulations of our country have also made clear requirements. In this paper, from 1959 to 19 1, 26 marine accidents of commercial aircraft passing through the structural integrity of aircraft are counted.
From the whole forced landing process, the first problem to improve the survival rate is to solve the fuselage fracture; From the perspective of aircraft manufacturing technology, the fuselage is generally divided into several separate manufacturing processes and then spliced. Due to the different mechanical parameters such as mass and inertia, the weak parts of the structure will break under the impact load of water medium. Right?
In the conceptual analysis stage, appropriate engineering simplification can be done, such as dividing the whole fuselage into 4-5 sections according to the structural characteristics of the fuselage, connecting them with plastic hinges, and setting the mass, inertia and centroid position of each section. Then consider simplifying the excitation of water medium. Firstly, the mechanical characteristics of joints and the influence of a series of parameters, such as the magnitude of excitation, the position of action point and the mechanical characteristics of various parts of the fuselage, are analyzed with simple force input, and then further research is carried out.
Before the plane touches the water, the wing can be separated from the fuselage, and the shape of the lower part of the fuselage can be changed through some devices, so that its interaction with water is more conducive to reducing the impact load. After the optimized load is determined by some streamlined designs similar to the bow, the fuselage skeleton structure and the pilot's landing procedures can be designed accordingly, so that the fuselage can enter the water in the best posture and ensure the integrity of the fuselage to the greatest extent.
When the helicopter makes an emergency landing on the water, the life safety of the crew and passengers can be guaranteed. The following is ... The model has carried out landing tests with different parameters such as landing speed, attitude, roll angle, yaw angle and sea state.