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