Narrative:

While cruising at 4500 ft between dmw and fdk; I saw a glider that appeared to be circling at 12 O'clock position; several hundred ft above me; several mi ahead. As I approached; I watched it closely. I determined that it was in fact circling in a steady path without any decrease in altitude; and I decided that there was enough room that I could safely pass underneath without changing altitude or taking other evasive action. While I was ready to dive if necessary; I held my altitude; and I continued to closely watch the glider until it disappeared above me. I briefly saw the glider through the small roof windows of the plane as I passed underneath it. I estimate that I was approximately 200-300 ft from the glider when I passed underneath it. While my attention at the time had been fully devoted to making sure that I could safely pass underneath the glider; in retrospect; I realize that the glider pilot had no way of knowing that -- and I probably gave him or her a serious scare as a result. I was probably too close for comfort; and it creates an open question of whether I was 'well clear' of the other aircraft; as required by the far's -- especially in light of the fact that the glider had the right-of-way. In the future; even if I think that I can safely pass another nearby aircraft without taking evasive action; I will do so with at least 500 ft of separation; and preferably more. I will also change position or altitude in a way that is visible to another pilot; so that he or she can see that I am; in fact; paying attention. Not only will that keep me from causing another pilot to be concerned; as I probably did in this case; but it would also give me a larger buffer zone in the event of any unexpected changes in path; position; or altitude that might result in a collision.

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Original NASA ASRS Text

Title: A C172 PILOT FLEW DIRECTLY UNDER A SAILPLANE WITH 300 FT VERTICAL CLEARANCE.

Narrative: WHILE CRUISING AT 4500 FT BTWN DMW AND FDK; I SAW A GLIDER THAT APPEARED TO BE CIRCLING AT 12 O'CLOCK POS; SEVERAL HUNDRED FT ABOVE ME; SEVERAL MI AHEAD. AS I APCHED; I WATCHED IT CLOSELY. I DETERMINED THAT IT WAS IN FACT CIRCLING IN A STEADY PATH WITHOUT ANY DECREASE IN ALT; AND I DECIDED THAT THERE WAS ENOUGH ROOM THAT I COULD SAFELY PASS UNDERNEATH WITHOUT CHANGING ALT OR TAKING OTHER EVASIVE ACTION. WHILE I WAS READY TO DIVE IF NECESSARY; I HELD MY ALT; AND I CONTINUED TO CLOSELY WATCH THE GLIDER UNTIL IT DISAPPEARED ABOVE ME. I BRIEFLY SAW THE GLIDER THROUGH THE SMALL ROOF WINDOWS OF THE PLANE AS I PASSED UNDERNEATH IT. I ESTIMATE THAT I WAS APPROX 200-300 FT FROM THE GLIDER WHEN I PASSED UNDERNEATH IT. WHILE MY ATTN AT THE TIME HAD BEEN FULLY DEVOTED TO MAKING SURE THAT I COULD SAFELY PASS UNDERNEATH THE GLIDER; IN RETROSPECT; I REALIZE THAT THE GLIDER PLT HAD NO WAY OF KNOWING THAT -- AND I PROBABLY GAVE HIM OR HER A SERIOUS SCARE AS A RESULT. I WAS PROBABLY TOO CLOSE FOR COMFORT; AND IT CREATES AN OPEN QUESTION OF WHETHER I WAS 'WELL CLR' OF THE OTHER ACFT; AS REQUIRED BY THE FAR'S -- ESPECIALLY IN LIGHT OF THE FACT THAT THE GLIDER HAD THE RIGHT-OF-WAY. IN THE FUTURE; EVEN IF I THINK THAT I CAN SAFELY PASS ANOTHER NEARBY ACFT WITHOUT TAKING EVASIVE ACTION; I WILL DO SO WITH AT LEAST 500 FT OF SEPARATION; AND PREFERABLY MORE. I WILL ALSO CHANGE POS OR ALT IN A WAY THAT IS VISIBLE TO ANOTHER PLT; SO THAT HE OR SHE CAN SEE THAT I AM; IN FACT; PAYING ATTN. NOT ONLY WILL THAT KEEP ME FROM CAUSING ANOTHER PLT TO BE CONCERNED; AS I PROBABLY DID IN THIS CASE; BUT IT WOULD ALSO GIVE ME A LARGER BUFFER ZONE IN THE EVENT OF ANY UNEXPECTED CHANGES IN PATH; POS; OR ALT THAT MIGHT RESULT IN A COLLISION.

Data retrieved from NASA's ASRS site as of January 2009 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.