A lighter than {HEAD ~ air} 1 wherein {TAIL ~ the image projection} means is operable to project an externally visible, variable image onto the projection surface 
A lighter than { HEAD ~ air } 1 wherein { TAIL ~ the image projection } means is operable to project an externally visible , variable image onto the projection surface
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH