A first generation of commercial amphibious hovercrafthas now been operating on a scheduled basis with revenue payloadson relatively-short over-water routes. On some of these routes,open-sea conditions prevail. By and large, the degree of successattained during these operations has been encouraging. However,certain problem areas have been brought to light, one or the mostimportant being concerned with handling qualities.As in the case of aircraft, the handling qualities ofhovercraft depend heavily on stability and control characteristics.In this case, however, the problem is rather more complex beingdependent on aerodynamic, hydrodynamic, and air-cushion effects.There are also important interference effects at the aero-hydro-interface. To understand the overall handling problem, each ofthese contributory effects must be isolated from the others, sothat individual study from a stability and control viewpoint canbe attempted.The task of isolation is difficult. It does not fallwithin the scope of full-scale testing, neither is it amenable toanalysis except possibly in the case of air-cushion effects wheregood progress has been made using mathematical analysis. Thusit becomes essential that to study the aerodynamic and hydrodynamiceffects, recourse be made to experimental testing. The NationalPhysical Laboratory at Feltham has provided most of the effort inhydrodynamic experimentation, and the Cranfield Institute ofTechnology (formerly known as the College of Aeronautics) hascomplemented this work by undertaking the aerodynamic experimentation.
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