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