The collective control for pitch change employs {HEAD ~ a coil spring} mounted between {TAIL ~ a pitch horn} and a hub 
mounted between
The collective control for pitch change employs { HEAD ~ a coil spring } mounted between { TAIL ~ a pitch horn } and a hub
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH