Problems of an Aerodynamic Interference between Helicopter Rotor Slipstream and an Elevated Heliport

An elevated heliport, as it has been defined by FAA (Federal Aviation Administration), is a heliport located on a rooftop or other elevated structure where the TLOF (touchdown and lift-off area) is at least 30 inches (76 cm) above the surrounding surface [1]. One of greatest advantages of such heliports is that they require less free space, which eases its build nearby existing buildings – especially in densely built-up areas. However, design of such heliports is more complicated, than ground level ones, while one must include an aerodynamic impact of the building below the elevated heliport and surrounding buildings. The aerodynamic interference between the helicopter and the buildings may result with decline of flight safety, due to sudden decrease of thrust (when flying above the edge of building) or because of increased turbulence in windy weather, wake behind surrounding buildings causing sudden gusts etc. Moreover, oscillations of pressure caused by helicopter rotor influence on the building structure also must be taken into account due to increased wear of upper part of the building or devices mounted on its roof (for example, elevator drives). These oscillation may also cause vibrations of building’s structure, which is especially important in case of medical heliports – which are a vast majority of elevated heliports (and heliports in general) – because of strict requirements for acceptable vibration level. The article is aimed on summarize aerodynamic issues, which should be taken into account during design of elevated heliport.