The total duct system thus constitutes {TAIL ~ a fixed intake aperture} feeding a configurable exhaust aperture through {HEAD ~ a volume and volume velocity driven turbine type fan}, 3 
The total duct system thus constitutes { TAIL ~ a fixed intake aperture } feeding a configurable exhaust aperture through { HEAD ~ a volume and volume velocity driven turbine type fan } , 3
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH