# Launch Bar Dynamics Character Analysis of Carrier-Based Aircraft Catapult Launch
## 1 Introduction  
The main role of the launch bar is to transmit the catapult force [1; 2; 3] to the aircraft, allowing the aircraft to accelerate while taxing before reaching a safe catapult end airspeed within the limited length deck. At the end of the catapult [4; 5; 6], the launch bar pops out of the shuttle. The launch bar, which is in the air, needs a mechanism for controlling and overcoming other damping torque. The launch bar may strike the flight deck if the restoring moment of the launch bar cannot overcome the other damping torque. Therefore, restraining the contrarotation of the launch bar is an important condition when ensuring the secure catapult launch of an aircraft. It is very important to research the characteristics of launch bar dynamics. When researching the launch bar for a catapult launch, [PERSON] [7] indicated that the launching system should consist of launch bar installation, cockpit controls and components, and holdback and release installation. [PERSON] [8] studied full-scale tests of nose tow catapulting, and showed that nose wheel tow catapulting was better than a bridle launching system. Reference [9] established a six-degree-of-freedom dynamics model of a catapult launch for carrier-based aircraft taking into consideration aircraft off-center position, and the launch bar load was calculated. Reference [10] carried out parametric models and optimization analyses of launch bar driving mechanisms. There weresome patents introduced concerning the installation of launch bars, for example, (a) an improved power-operated launching system for aircraft [11]; (b) launching and holdback gear designed around the nose landing gear of the aircraft [12]; (c) a launch bar pivotally mounted on the oleo strut torque links [13]; (d) a control mechanism for controlling a catapult bar [14]; and (e) a nose gear assembly using one nose wheel for a catapult-launched airplane [15]. However, there is no literature on the characteristics of launch bar dynamics after the launch bar automatically disengages from the shuttle at the end of the power stroke. On the basis of the security of a catapult launch for carrier-based aircraft, Reference [8] indicated that nose wheel tow would increase the safety of the flight deck. [PERSON] [16] researched catapult criteria for carrier-based airplanes. Many studies were carried out on the problem of the main gear's off-center location for the catapult launch of carrier-based aircraft [7; 9; 17; 18; 19; 20]. Reference [21] indicated that the catapult minimum end airspeed was the airspeed value that could be safely tested aboard an aircraft carrier. In Reference [22], a total of 39 launching tests were performed during the first test campaign; the conclusion was that the launch bar retraction system had to be improved. Further research on catapult launch mainly focused on the effect of deck motion [23; 24; 25], the control problems of the climbing stage [26; 27; 28; 29], the effect of nose landing gear's sudden extension [30; 31; 32], the analysis of aircraft-carrier parameter matching [33; 34], and so on. However, despite all public documents in regard to catapult launch around the world, there is a lack of research on the effect of the characteristics of launch bar dynamics on the security of the catapult launch after the launch bar automatically disengages from the shuttle at the end of the power stroke. This paper made great efforts toward the goal of analyzing the characteristics of launch bar dynamics. This article built a mathematical model of catapult launch, including a launch bar dynamics model, and analyzed the effect of some factors on the characteristics of launch bar dynamics, such as the mass of the launch bar, the center of gravity position of the launch bar, and the restoring moment of the launch bar.