Patent ID: 7972984
Filing Date: 2011-07-05
Classification: B32B,B64F,E01C,Y10T

Abstract:
1. A mat for reducing the disturbance of particulate matter by wind created during the landing of a helicopter on the mat when the mat is placed on the particulate matter, the mat comprising: (a) a first wind permeable layer of mesh material; and (b) a second wind permeable layer of mesh material, wherein: the first layer is held in a substantially fixed position on top of the second layer without an intervening layer between the first and second layers, and the first layer is attached to the second layer in a peripheral region; the first and second layers of mesh material each are a knitted material with an average stitch length of between 2 mm and 6 mm; the average separation between the first layer and the second layer is between 2 mm and 10 mm; each layer of the mesh material has a porosity of between 10% and 50%, the porosity being the proportion of surface area of the mesh material which consists of holes rather than fibers; and each layer of the mesh material has a wind attenuation factor of between 40% and 80% for wind directed at right angles onto the mesh material at 50 km/h based on the average stitch length, the average separation, and the porosity of the first and second mesh layers.