PLT OF PIPER CUB FLEW BELOW MSA OVER A CITY AND HAD NMAC WITH A GOV HELI.

Narrative

ON OCT/XX/94; I WAS FLYING A PIPER CUB OVER DOWNTOWN DAYTON; OH; TAKING PHOTOGRAPHS WITH A FRIEND. THE GND ELEVATION VARIES SLIGHTLY; BUT 950 FT IS THE APPROX AVERAGE. DUE TO THE LACK OF MANY OFF-FIELD LNDG SITES WITHIN THE CITY; I HAD BEEN SPECIFICALLY MONITORING MY ALT; VERY FREQUENTLY; WHILE OVER THE CITY TO TRY AND MAINTAIN 1000 FT AGL. WHILE CIRCLING A HOUSE; I DID ALLOW THE ACFT TO INADVERTENTLY DROP TO JUST ABOVE 1700 FT MSL (750 FT AGL) ON 1; POSSIBLY 2 OCCASIONS; BUT UPON NOTICING THAT; I CLBED BACK UP TO APPROX 1950 FT MSL. AFTER CIRCLING; WE HEADED IN A SSE DIRECTION; NOT OVER ANY TALL BUILDINGS; BACK TOWARDS THE ARPT WE TOOK OFF FROM. WHILE JUST S OF THE DOWNTOWN AREA; AND JUST OVER A MAJOR E/W RUNNING FREEWAY; THE PAX POINTED OUT; AND THEN I IMMEDIATELY SAW THROUGH THE OVERHEAD SKYLIGHT BTWN THE WINGS; A SMALL HELI FLY OVER US IN AN EASTERLY DIRECTION. ALTHOUGH I HAD BEEN CLRING CONSTANTLY THROUGHOUT THE FLT; I DID NOT SEE IT APCH US DUE TO IT BEING OBSCURED BY THE R WING. WHILE IT APPEARED TO BE CLOSE; IT DID NOT APPEAR TO BE MAKING ANY KIND OF EVASIVE MANEUVER. I DO NOT REMEMBER MY EXACT ALT AT THAT MOMENT; BUT BECAUSE I WAS SO NEAR THE DOWNTOWN AREA WHERE WE HAD BEEN CIRCLING; I AM SURE I WAS AT LEAST CLOSE TO THE 1000 FT AGL THAT I HAD BEEN TRYING TO MAINTAIN. AS SOON AS WE REACHED THE SPARSELY POPULATED AREAS JUST SE OF TOWN; I ALLOWED US TO DSND TO APPROX 500 FT AGL; BUT THEN CLBED ANOTHER HUNDRED FT OR SO FOR THE FLT BACK TO WAYNESVILLE; OH; WHERE WE HAD DEPARTED FROM. UPON LNDG; I NOTICED A SMALL 2-SEAT HELI LNDG ON THE FIELD BESIDE US; AND REALIZED THEY WERE PROBABLY THERE TO TALK TO ME. THEY TOLD ME THEY HAD BEEN AT 500 FT AGL CHASING A STOLEN CAR WHEN THEY FLEW OVER US. THEY MADE NO MENTION OF AN EVASIVE MANEUVER SUCH AS A CLB OR A TURN TO AVOID US. HE THEN TOOK DOWN MY LICENSE NUMBER AND NAME; AND STATED HE WOULD RPT THE INCIDENT TO THE FAA. I ALSO NOTED THAT OUR ACFT ALTIMETER INDICATED WITHIN 10 FT OF FIELD ELEVATION. BESIDES THE OBVIOUS EMBARRASSMENT OF BEING CHASED DOWN BY A HELI; A COUPLE OF OTHER THINGS ABOUT THE WHOLE EVENT DISTURB ME. FIRST; WHILE I WAS NOT FLYING THIS ACFT PRECISELY AND BY THE INSTS DURING MOST OF THE FLT; ON THE PORTION OF THE FLT WHERE THE INCIDENT OCCURRED; I HAD BEEN SPECIFICALLY MONITORING MY ALT. I REALIZE THAT I DROPPED BELOW 1000 FT AGL AT LEAST ONCE INADVERTENTLY; AND WHILE A DROP OF 1 FT OR 500 FT BELOW THAT CONSTITUTES A VIOLATION; I AM ABSOLUTELY SURE I WAS NOWHERE NEAR THE 350 FT AGL TO 450 FT AGL (1300 FT MSL TO 1400 FT MSL) THAT THEY CLAIMED I WAS AT WHEN THEY OVERFLEW ME AT AN ALLEGED 1500 FT MSL. THOUGH I DO NOT QUESTION THE INTEGRITY OF THOSE OFFICERS; I DO BELIEVE THAT WHILE I MAY POSSIBLY HAVE BEEN A LITTLE LOW; THEY; PREOCCUPIED WITH THE CHASE; MAY HAVE BEEN HIGHER THAN THEY THOUGHT; AND HENCE THE INCIDENT OCCURRED. IN THAT CASE; I WOULD HAVE STILL BEEN IN THE WRONG; BUT AGAIN; I REALLY DON'T THINK THAT I WAS BELOW 1000 FT AGL SINCE I HAD BEEN MONITORING MY ALT AT THE TIME TO TRY AND ENSURE THAT I AT LEAST MAINTAINED THAT ALT. I BELIEVE THAT PROB COULD HAVE BEEN AVOIDED HAD I TRIED TO MAINTAIN AN EXTRA 100 OR 200 FT ALT OVER THE CITY; ESPECIALLY DUE TO THE LOW PWR SETTING; TIGHT TURNS; AND GUSTING WIND. CONTRIBUTING TO MY DECISION TO REMAIN RIGHT AT THE 1000 FT AGL LEVEL WAS THE DESIRE TO ACHIEVE THE BEST POSSIBLE PHOTOS. IN ADDITION; ALTHOUGH I HAD BEEN CLRING; BANKING OCCASIONALLY WHILE IN STRAIGHT FLT WOULD HELP ME TO SEE THROUGH THE BLIND SPOTS INHERENT TO HIGH WING ACFT. HOWEVER; I ALSO BELIEVE THAT THE HELI MAY HAVE BEEN WATCHING THE GND A LITTLE MORE THAN THEY SHOULD HAVE BECAUSE; FROM THEIR DESCRIPTION OF THE EVENT; IT SEEMED THEY DIDN'T SEE ME UNTIL THEY WERE RIGHT OVERHEAD. AND; THEY MAY NOT HAVE BEEN PAYING MUCH ATTN TO THEIR ALTIMETER EITHER. REGARDLESS OF THE ALTS; IT IS OBVIOUS THAT BOTH MYSELF AND THEY SHOULD HAVE BEEN USING BETTER CLRING TECHNIQUES.