Narrative:

Our flight originated from bdr as a part 61 training flight. A call to the FSS was made by my student to determine the local WX conditions, forecasts as well as any NOTAM's. I decided to let my student pick the best field and points for the ground reference maneuvers we would be practicing. After circling around our point about 4 times we noticed a C172 in close proximity to us that was maneuvering to follow our flight path. One time I was close enough to read the tail numbers and saw the last two digits were 'xx.' I knew that this was a state police aircraft at that point. I then thought that the pilot was just to check us out and possibly leave after they determined that we were conducting ground reference maneuvers. Remembering the aircraft intercept procedures, I monitored 121.5. I did not hear any transmission to our aircraft in any form. This led me to believe that we were fine. We then decided to practice s-turns across railroad tracks that run north to south. During the maneuvering, I was scanning for other traffic like always, but I could not see the C172 that was previously near me. After turning again, I saw that he was directly behind me which was impossible to see without a turn. I then decided to leave the area and head back to bdr to end the lesson, when I then noticed a second C172 in close proximity to the previous C172. I then decided to make a landing at the nearest airport mmk as we were approximately 5 miles to the south of the airport at that time. I parked on the ramp and waited for the C172 who followed me in and we both shut down and talked. I expressed my concern that I did not hear anything on 121.5 which would have helped if they did want me to land. Another concern was that the aircraft markings were tough to tell if it was a state police aircraft. The officer also told me that they were concerned about the close proximity of our aircraft to a reservoir. On the sectional it basically looked like a small lake, and from the air, it was the same thing. Therefore, our encounter may have been avoided if we knew that this was a target of interest by law enforcement. I believe it would be good to give this information out to local flight instructors.

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Original NASA ASRS Text

Title: PLTS OF PA28 MADE PRECAUTIONARY LNDG AFTER BEING SHADOWED BY STATE POLICE ACFT DURING TRAINING FLT.

Narrative: OUR FLT ORIGINATED FROM BDR AS A PART 61 TRAINING FLT. A CALL TO THE FSS WAS MADE BY MY STUDENT TO DETERMINE THE LCL WX CONDITIONS, FORECASTS AS WELL AS ANY NOTAM'S. I DECIDED TO LET MY STUDENT PICK THE BEST FIELD AND POINTS FOR THE GND REFERENCE MANEUVERS WE WOULD BE PRACTICING. AFTER CIRCLING AROUND OUR POINT ABOUT 4 TIMES WE NOTICED A C172 IN CLOSE PROXIMITY TO US THAT WAS MANEUVERING TO FOLLOW OUR FLT PATH. ONE TIME I WAS CLOSE ENOUGH TO READ THE TAIL NUMBERS AND SAW THE LAST TWO DIGITS WERE 'XX.' I KNEW THAT THIS WAS A STATE POLICE ACFT AT THAT POINT. I THEN THOUGHT THAT THE PLT WAS JUST TO CHK US OUT AND POSSIBLY LEAVE AFTER THEY DETERMINED THAT WE WERE CONDUCTING GND REFERENCE MANEUVERS. REMEMBERING THE ACFT INTERCEPT PROCS, I MONITORED 121.5. I DID NOT HEAR ANY TRANSMISSION TO OUR ACFT IN ANY FORM. THIS LED ME TO BELIEVE THAT WE WERE FINE. WE THEN DECIDED TO PRACTICE S-TURNS ACROSS RAILROAD TRACKS THAT RUN N TO S. DURING THE MANEUVERING, I WAS SCANNING FOR OTHER TFC LIKE ALWAYS, BUT I COULD NOT SEE THE C172 THAT WAS PREVIOUSLY NEAR ME. AFTER TURNING AGAIN, I SAW THAT HE WAS DIRECTLY BEHIND ME WHICH WAS IMPOSSIBLE TO SEE WITHOUT A TURN. I THEN DECIDED TO LEAVE THE AREA AND HEAD BACK TO BDR TO END THE LESSON, WHEN I THEN NOTICED A SECOND C172 IN CLOSE PROXIMITY TO THE PREVIOUS C172. I THEN DECIDED TO MAKE A LNDG AT THE NEAREST ARPT MMK AS WE WERE APPROX 5 MILES TO THE S OF THE ARPT AT THAT TIME. I PARKED ON THE RAMP AND WAITED FOR THE C172 WHO FOLLOWED ME IN AND WE BOTH SHUT DOWN AND TALKED. I EXPRESSED MY CONCERN THAT I DID NOT HEAR ANYTHING ON 121.5 WHICH WOULD HAVE HELPED IF THEY DID WANT ME TO LAND. ANOTHER CONCERN WAS THAT THE ACFT MARKINGS WERE TOUGH TO TELL IF IT WAS A STATE POLICE ACFT. THE OFFICER ALSO TOLD ME THAT THEY WERE CONCERNED ABOUT THE CLOSE PROXIMITY OF OUR ACFT TO A RESERVOIR. ON THE SECTIONAL IT BASICALLY LOOKED LIKE A SMALL LAKE, AND FROM THE AIR, IT WAS THE SAME THING. THEREFORE, OUR ENCOUNTER MAY HAVE BEEN AVOIDED IF WE KNEW THAT THIS WAS A TARGET OF INTEREST BY LAW ENFORCEMENT. I BELIEVE IT WOULD BE GOOD TO GIVE THIS INFO OUT TO LOCAL FLT INSTRUCTORS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.