Aircraft ditching: a free surface / free motion problem

Within a national research project on aircraft dynamic loads and resultant structural response the task was given to investigate aircraft emergency landings on water, generally called “ditching”. The work was initiated and funded by Airbus Industries. As controlled experiments for such events are costly and difficult to extrapolate to full-scale, the study at HSVA was completely based on computer simulations. The commercial RANS solver “Comet” was used to determine the path of the aircraft fuselage from initial conditions in air given at t = 0. After being released in air, the aircraft fuselage was free to react on the forces and moments developing at the free surface. In order to simplify the approach the hydrodynamic forces were derived in all details by the RANS simulation while the aerodynamic forces and moments were approximated. Simultaneously, the simulations were performed at the TUHH using the program “Ditch”, based on an extension of the “momentum method” developed by von Karman and Wagner. The results are presented in this paper for generic fuselage shapes called A-, D- and J-Body in terms of motion histories and section forces.