Title: IMPROVEMENTS IN AND RELATING TO AIR VEHICLES Inventors: George Ninkovich Ted Kellogg Ray Lim An air vehicle primarily for use as a flying billboard has a spherical envelope which contains a lighter-than-air gas and at least four individual fan units carried by the envelope and operable to displace the envelope vertically and laterally for maneuvering the air vehicle. A fan unit which may be used in the air vehicle or for other fan applications has a rotary fan blade located in a dish-shaped housing so that there is an annular gap between the blade and the wall of the housing through which air is drawn into or expelled from the housing depending on the direction of blade rotation.
