The method also includes the step of sensing {HEAD ~ a parameter} representative of {TAIL ~ air flow} through the hole 
The method also includes the step of sensing { HEAD ~ a parameter } representative of { TAIL ~ air flow } through the hole
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH