French Marine Air Cushion Vehicles

Extract

The first research carried out in France relating to air cushions was effected in 1957 by the Bertin Company. The phenomenon was first observed during thrust measurements on inward directed annular jet silencers (Fig. 1), in which the effects of air inlets were being studied. Thrust was measured by the weighing of a plate located in front of the nozzle; when the secondary air inlets were closed, the scheme was in fact the one of the peripheral jet air cushion and the thrust read on the dynamometer was found to be much greater than the theoretical jet thrust (Fig. 2).

It should be noted that this work was an extension of research carried out by SNECMA concerning striction, that is to say the control of the exit area of the engine nozzle by means of an inward directed peripheral fluid curtain the purpose of which was to increase the pressure inside the exhaust pipe which is the characteristic of annular jet air cushions (Fig. 3).