BY 1973, AFTER TWO YEARS IN OPERATION, THE HELICOPTER UNITS HAD, INDEED, LOWERED THEIR RESPONSE TIME ON ALL CALLS FOR SERVICE TO AN AVERAGE OF FOUR MINUTES COMPARED TO SIX MINUTES FOR GROUND UNITS. HOWEVER, THE IN-THE-ACT ARREST RATE FOR THE DEPARTMENT REMAINED VERY LOW. ONLY 0.06 PERCENT OF THE ARMED ROBBERIES AND 0.01 PERCENT OF THE BURGLARIES WERE STOPPPED IN-THE-ACT. POLICE OFFICERS REALIZED THAT IF THE ASSUMPTION THAT FASTER RESPONSE TIMES DO LEAD TO INCREASED ARRESTS WAS VALID, THEN THE RESPONSE TIME NEEDED TO BE FURTHER REDUCED TO ACHIEVE THE DESIRED RESULTS. OTHER RESULTS SEEMED TO INDICATE THAT THE PRESENCE OF THE HELICOPTERS PREVENTED SOME CRIME THAT NORMALLY WOULD HAVE OCCURRED. (AUTHOR ABSTRACT MODIFIED)