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