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