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