{TAIL ~ The flaps} are biased towards {HEAD ~ the extended position}, and normally retained in the inner position by retaining devices 
{ TAIL ~ The flaps } are biased towards { HEAD ~ the extended position } , and normally retained in the inner position by retaining devices
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH