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A first generation of commercial amphibious hovercraft
has now been operating on a scheduled basis with revenue payloads
on relatively-short over-water routes. On some of these routes,
open-sea conditions prevail. By and large, the degree of success
attained during these operations has been encouraging. However,
certain problem areas have been brought to light, one or the most
important being concerned with handling qualities.
As in the case of aircraft, the handling qualities of
hovercraft depend heavily on stability and control characteristics.
In this case, however, the problem is rather more complex being
dependent 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 of
these contributory effects must be isolated from the others, so
that individual study from a stability and control viewpoint can
be attempted.
The task of isolation is difficult. It does not fall
within the scope of full-scale testing, neither is it amenable to
analysis except possibly in the case of air-cushion effects where
good progress has been made using mathematical analysis. Thus
it becomes essential that to study the aerodynamic and hydrodynamic
effects, recourse be made to experimental testing. The National
Physical Laboratory at Feltham has provided most of the effort in
hydrodynamic experimentation, and the Cranfield Institute of
Technology (formerly known as the College of Aeronautics) has
complemented this work by undertaking the aerodynamic experimentation. |
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