Simulation And Research Of Lightning Indirect Effects On The Aircraft

Aircrafts fly in the atmosphere will inevitably encounter lightning environment, resulting any safety incidents, and some even catastrophic. In particular, modern electronic technology and a large number of advanced composite materials are adopted, improving the performance and economic efficiency of the flight, but also bringing more lightning accidents. The hazards of lightning to aircraft include direct effect (physical effects) and indirect effect (electromagnetic effects). Although lightning current may not directly contact with the electrical wiring in the aircraft, but it may be coupled to the aircraft interior by resistance coupling, magnetic coupling and electric coupling mechanism, and producing induction voltage and current surge, thus causing a disturbance or damage, this is lightning indirect effect. In order to obtain airworthiness certificate civil aircraft must take the whole laboratory lightning indirect effect protection test, but, lightning test is time-consuming and aircraft parts are damaged after the lightning test generally. Therefore, in this paper, the numerical simulation technology is used to simulate the aircraft lightning indirect effects, provide some theoretical data for large aircraft development programs in our country.According to the types of active mainstream aircraft, this paper designs three plane models:Seminole PA44 small transport aircraft which is whole metals, Airbus A350 large transport aircraft and AS350B3 helicopter, and builds 5 types of cable in different regions: single core cable, twisted pair, coaxial cable, shielded wire, shielded twisted pair. The CST electromagnetic simulation software based on the transmission line matrix method is used to simulate surface current distribution, the regional transient distribution of magnetic field and internal cable coupling situations when the flying aircraft suffered by the lightning strike in the different conditions. In the simulation high current pulse injection method is used, and set different paths, different lightning current model according to the relevant norm.Through the simulation test, the results show that:as lightning path changing, surface current distribution will change, the regional value of the transient magnetic field also will change, the current density and magnetic field of the lightning strike point area may be strongest, the area of lightning current channel, the door gap around and the larger radius of curvature may be smaller; the amplitude of lightning transient induced current in the cable increases linearly with the increase of growth of lightning current, decreases linearly with rise time, but does not affected by the decline in fall time; aluminum can provide good shielding for its internal equipment and wire, the shielding effect of CFRP composite was worse than aluminum, such as helicopter fuselage material settings as CFRP, the shielding efficiency is about 15dB, setting as aluminum the shielding efficiency is about 70dB; the lightning induced current of cable is greatly affected by the way of laying, installing shielding layer or the metal conduit outside cables can effectively reduce the lightning induced currents, when a shield layer is added on the twisted pair, the effect is more obvious; the larger the size of the aircraft, the regional transient magnetic field strength and internal induced current of cable smaller. It can be seen that the study of the indirect effects of aircraft lightning must pay attention to the factors:Lightning path, lightning current model, body material, aircraft size and shape, laying method of cables.