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