{HEAD ~ a rotor blade} rotated in {TAIL ~ synchronism} with said second sprocket drum to actuate said hinged door panel momentarily open on each half revolution of said rotor blade 
rotated in
{ HEAD ~ a rotor blade } rotated in { TAIL ~ synchronism } with said second sprocket drum to actuate said hinged door panel momentarily open on each half revolution of said rotor blade
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH