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