The invention provides a back up supply, by putting the air through a plenum chamber and dividing it so that when cooling airflow is reduced, {HEAD ~ a further sealing air flow} is provided in {TAIL ~ compensation} therefore 
The invention provides a back up supply , by putting the air through a plenum chamber and dividing it so that when cooling airflow is reduced , { HEAD ~ a further sealing air flow } is provided in { TAIL ~ compensation } therefore
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH