Search Results (2)

Catapult-assisted takeoff is the initiation of flight missions for carrier-based aircrafts. Ensuring the safety of aircrafts during catapult-assisted takeoff requires a thorough analysis of their motion characteristics. In this paper, a rigid–flexible coupling model using the Finite Element Method and Multibody Dynamics (FEM-MBD) approach is developed to simulate the aircraft catapult process. This model encompasses the aircraft frame, landing gear, carrier deck, and catapult launch system. Firstly, reasonable assumptions were made for the dynamic modeling of catapult-assisted takeoff. An enhanced plasticity algorithm that includes transverse shear effects was employed to simulate the tensioning and release processes of the holdback system. Additionally, the forces applied by the launch bar and holdback bar, nonlinear aerodynamics loads, shock absorbers, and tires were introduced. Finally, a comparative analysis was conducted to assess the influence of different launch bar angles and holdback bar fracture stain on the aircraft’s attitude and landing gear dynamics during the catapult process. The proposed rigid–flexible coupling dynamics model enables an effective analysis of the dynamic behavior throughout the entire catapult process, including both the holdback bar tensioning and release, takeoff taxing, and extension of the nose landing gear phases. The results show that higher launch bar angle increase the load and extension of the nose landing gear and cause pronounced fluctuations in the aircraft’s pitch attitude. Additionally, the holdback bar fracture strain has a significant impact on the pitch angle during the first second of the aircraft catapult process, with greater holdback bar fracture strain resulting in larger pitch angle variations. Full article

The release load of holdback bar will affect the safety of catapult-assisted takeoff of carrier-based aircraft, and the accurate control of releasing the load will ensure success. The magnitude and the control accuracy of release load are important parameters which impact the takeoff performance, therefore unstable release load and insufficient release precision are the main factors affecting the takeoff safety. In this paper, mechanical models of the carrier-based aircraft in the catapult-assisted takeoff tensioning state and gliding state after release are established based on multi-body dynamics, contact mechanics and tribological theory, and the influence of the release load of the holdback bar on the catapult-assisted takeoff performance is analyzed. Furthermore, a kinetic model of the holdback bar device is established, and the kinetic characteristics of the release process of the holdback bar are studied. Based on the kinetic model and friction model of the holdback bar, the influencing factors of the sensitivity of the holdback bar release load are analyzed and the structural parameters are optimized. The results show that the released load decreases slowly with the increase of the contact surface angle of the holdback bar structure and increases rapidly when that angle reaches the critical value; besides, the release load increases slowly with the increase of the friction coefficient of the contact surface and increases faster when the critical friction coefficient is reached. Full article