Vehicles for travelling over land and/or water

Claim 1

A VEHICLE FOR TRAVELLING OVER LAND AND/OR WATER WHICH IS SUPPORTED ABOVE THE SURFACE OVER WHICH IT IS OPERATING BY AT LEAST ONE CUSHION OF PRESSURISED FLUID, THE CUSHION BEING CONTAINED ROUND AT LEAST PART OF ITS PERIPHERY BY A FLUID CURTAIN FORMED BY FLUID FLOWING FROM A SUPPLY PORT BETWEEN THE BOTTOM SURFACE OF THE VEHICLE AND THE SURFACE OVER WHICH THE VEHICLE IS OPERATING, COMPRISING MEANS FOR SENSING AND PRODUCING SIGNALS INDICATIVE OF VARIATIONS IN AT LEAST ONE OF THE FOLLOWING PARAMETERS, VARIATION OF WHICH IS INDICATIVE OF A NEED FOR VARIATION IN THE STRENGTH OF THE FLUID CURTAIN, (A) THE PRESSURE DIFFERENTIAL ACROSS THE FLUID CURTAIN, (B) THE HEIGHT OF THE SUPPLY PORT ABOVE THE SURFACE OVER WHICH THE VEHICLE IS OPERATING, AND (C) THE ANGLE OF FLOW OF THE CURTAIN FORMING FLUID RELATIVE TO THE BOTTOM SURFACE OF THE VEHICLE, AND MEANS RESPONSIVE TO SAID SIGNALS FOR ADJUSTING THE MASS FLOW OF THE FLUID FORMING THE FLUID CURTAIN AT ANY LOCALITY ROUND THE CIRCUMFERENCE OF THE FLUID CURTAIN TO THAT REQUIRED TO SUSTAIN THE CUSHION IN THE CONDITIONS PREVAILING AT THAT LOCALITY, SAID LAST NAMED MEANS BEING OPERATIVE TO REDUCE THE MASS FLOW OF THE CURTAIN FORMING FLUID WHEN SAID PARAMETER SENSING MEANS PRODUCES A SIGNAL INDICATIVE OF A DECREASE IN AT LEAST ONE OF SAID PARAMETERS.