A fan, having {HEAD ~ blades} adapted to operate in {TAIL ~ at least two positions} comprising, 
adapted to operate in
A fan , having { HEAD ~ blades } adapted to operate in { TAIL ~ at least two positions } comprising ,
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH