By this, {HEAD ~ unnecessary frequent swiveling} of {TAIL ~ the nacelle} is avoided and also a large amount of electricity for swiveling the nacelle is saved 
By this , { HEAD ~ unnecessary frequent swiveling } of { TAIL ~ the nacelle } is avoided and also a large amount of electricity for swiveling the nacelle is saved
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH