This paper documents progress in rotorcraft crashworthiness research and development that has been realized during the past forty years. Trends are presented in several categories including: facilities and equipment for conducting crash testing, updated crash certification requirements, the application of crash modeling and simulation techniques, and rotorcraft structural design for improved crash performance focusing on the application of advanced composite materials. Likely one of the most important advances is the ability to rapidly simulate crash impacts and to see the effects of design changes on the impact response. Enhanced dynamic computer simulations have greatly improved automotive safety today and are making inroads in the aerospace community. Consequently, a detailed discussion of advances in crash modeling and simulation is presented. The paper concludes with a list of suggested recommendations, such that the progress made to date can be continued into the future.

A rotorcraft roof composite sandwich panel has been redesigned to optimize sound power transmission loss (TL) and minimize structure-borne sound for frequencies between 1 and 4 kHz where gear meshing noise from the transmission has the most impact on speech intelligibility. The roof section, framed by a grid of ribs, was originally constructed of a single honeycomb core/composite facesheet sandwich panel. The original panel has acoustic coincidence frequencies near 600 Hz, leading to poor TL across the frequency range of 1 to 4 kHz. To quiet the panel, the cross section was split into two thinner sandwich subpanels separated by an air gap. The air gap was sized to target the fundamental mass-spring-mass resonance of the panel system to less than 500 Hz, well below the frequency range of interest. The panels were designed to withstand structural loading from normal rotorcraft operation, as well as 'man-on-the-roof' static loads experienced during maintenance operations. Thin layers of viscoelastomer were included in the facesheet ply layups, increasing panel damping loss factors from about 0.01 to 0.05. Transmission loss measurements show the optimized panel provides 6-11 dB of acoustic transmission loss improvement, and 6-15 dB of structure-borne sound reduction at critical rotorcraft transmission tonal frequencies. Analytic panel TL theory simulates the measured performance within 3 dB over most frequencies. Detailed finite element (FE)/boundary element (BE) modeling simulates TL slightly more accurately, within 2 dB for frequencies up to 4 kHz, and also simulates structure-borne sound well, generally within 3 dB.