Abstract: An apparatus is provided for effecting rapid changes in the geometry of a flexible wall structure forming at least a part of the cushion seal on an air cushion vehicle. The apparatus comprises one or more inflatable members co-operating with the flexible wall structure and an air ejector for rapidly introducing pressurized air into each inflatable member. Each inflatable member may be constituted by a wall structure portion of hollow construction. The invention finds particular application in assisting directional control of an air cushion vehicle.

Abstract: The inflated geometry of an inflatable skirt wall constituting at least a part of the cushion sealing means on an air cushion vehicle (A.C.V.) is changed to effect a shift in the center of pressure of the vehicle supporting air cushion for assisting in directional control or to reduce the overall width dimension of the A.C.V. when the skirt wall projects outwardly of vehicle rigid body structure while maintaining a skirt structure sufficient to contain an air cushion for slow speed maneuvering of the A.C.V. Means for changing the inflated skirt wall geometry comprise duct means and co-operating valve means for controlling supply of pressurized air to one or more compartments of the skirt structure, and further duct means and co-operating valve means for venting air from said one or more compartments.