# Dynamics Test Research of Bounce of Carrier-Based Aircraft Arresting Hook
## 3 Test Key Technology  
### Simulation of Cushioning Performance of Main Landing Gear  
When the carrier-based aircraft lands, the arresting hook head usually touches the deck firstly, followed by the main landing gear tire. According to the dynamic simulation of the whole aircraft landing, the time gap between the contact of arresting hook, tires of main landing gear, and deck of aircraft carrier is in magnitude of 0.01 s, but no more than 0.1 s. Through the dynamic simulation of the carrier aircraft's landing, the curve of bounce height of the arresting hook and the stroke curve of the main landing gear buffer are obtained, as shown in Figure 2. It can be seen from the Figure 2 that the main landing gear buffer starts to compress after the arresting hook touches the deck in about 0.035 s. The time of the first positive stroke of the main landing gear buffer is 0.18 s, while the process of the first bounce of the hook is 0.08 s, and the time of the second bounce is 0.115 s. In the process of the first bounce and the second bounce of the hook, the aircraft is moving with the compression of the main landing gear buffer. The involved movement of the arresting hook with the fuselage has a certain influence on the whole bounce process, which cannot be ignored.  
Figure 2: Curves of hook bounce height and main landing gear stroke length.  
In the collision rebound test system of the arresting hook, the buffer performance of the main landing gear is simulated by installing a buffer under the basket. The buffer mainly needs to meet two requirements: first, the time of the first positive stroke should be consistent with that of the main landing gear in the simulation results; second, the compression of the first positive stroke should be consistent with that of the main landing gear in the simulation results. In this way, it can be ensured that the trajectory of the collision rebound of the arresting hook obtained in the test is closer to the actual situation.  
According to the total weight of the basket and the arresting hook, considering the friction and aerodynamic resistance when the basket falls freely, an oil-gas buffer is designed, which is installed under the basket to cushion the basket, and its internal structure is shown in Figure 3.  
Through the one-dimensional simulation platform Siemens LMS Imagine. Lab AMESim, the hydraulic system model of the buffer is established and the dynamic simulation of the basket falling is carried out. The simulation model is shown in Figure 4. With the aid of simulation, the filling parameters of buffer are optimized, and the simulation results are verified and corrected by using the real basket drop test to determine the filling parameters used in the final test.  
As the weight of the basket and the arresting hook is determined, the buffer performance is consistent with that of the main landing gear during landing by changing the filling of the buffer. The main performance indicators are the maximum buffer stroke and the time required for the first positive stroke. Carry out dynamic simulation on buffer performance, obtain a set of preliminary filling parameters, change the amount of filling oil and filling pressure of buffer, carry out multiple drop tests of the basket, and iteratively modify the filling parameters, so that its buffer performance is consistent with that of the main landing gear in the dynamic simulation of the whole aircraft landing at the same sinking velocity. The flow diagram of the determination of the damper filling is shown in Figure 5.  
Figure 3: Structure chart of damper.