Some of the air leaks radially outwards, to seal {HEAD ~ the gas annulus} against hot gas leaks onto {TAIL ~ the face} of the turbine disc 
Some of the air leaks radially outwards , to seal { HEAD ~ the gas annulus } against hot gas leaks onto { TAIL ~ the face } of the turbine disc
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH