DRI-KRASH Simulation of an UH-1D Drop Test and Generation of Acceleration Pulses

Kurzfassung

The first helicopter drop test in the EU funded project ‘HeliSafe TA’ was carried out in May 2005 at CIRA’s test facility LISA with a Bell UH-1D helicopter. DLR generated the DRI-KRASH model of the UH-1D helicopter and carried out simulations of the planned drop test scenario as well as of different other impact scenarios. As DLR is the only partner in HeliSafe TA with a validated mathematical model of the tested helicopter type, these simulations became even more important after it was found out that the drop test was not carried out with the planned impact conditions and the acceleration pulses (in the test) were not survivable and therefore not suitable for the HeliSafe TA sled test programme. Therefore, the consortium decided that DLR should generate acceleration pulses for the sled tests that represent the situation in the planned impact scenario in the best possible way. For this purpose, the KRASH model of the Bell UH-1D had to be changed and improved. Where available, the drop test results were compared with the results of simulations with the actual impact velocities. The required modifications to the DRI-KRASH model include for example changes in the mass distribution, in characteristics of plastic hinges, in beam failure loads and in friction coefficients. A series of simulation runs was carried out until a relatively good correlation with the test results was achieved and major occurrences like the failing of the landing gear or the tail boom were matched in a satisfactory way. Then, simulations were again carried out with the originally planned impact conditions.