Alternatively, {HEAD ~ a stirring means} can be used, such as a rotating prop or {TAIL ~ blade} 
such as
Alternatively , { HEAD ~ a stirring means } can be used , such as a rotating prop or { TAIL ~ blade }
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL