Experimental observations of an 8ms-1 drop test of a metallic helicopter underfloor structure onto a hard surface: part 1

Abstract: This is the first part of a two-part paper that describes the experimental observations for two similar sections of floor that were dropped onto both hard and water surfaces at 8 m/s, as a part of one experimental campaign. The current paper provides an assessment of a simple box-beam underfloor structure typically found in metallic helicopters and provides an overview of the failure modes and the collapse mechanism observed when dropped onto a hard surface. All findings are supported by quantitative measurements and extensive photographic evidence. The current paper identifies two limitations with the existing design, which are based upon the observations of the failure modes for different frame types and the performance of the intersection joints. In order to increase the level of crashworthiness currently offered, significant frame and joint redesign is required in order to provide a more progressive collapse. The simple buckling modes currently observed should be avoided, as the existing stroke is not fully utilized in the event of a crash, resulting in an inefficient structure. The current paper also discusses the sensitivity to impact angle, as slight variations from a normal impact may result in a detrimental response.