Narrative:

I departed ZZZ airport and turned west. I was soaring engine off in thermal lift at 3;000 feet when my traffic detector alerted me to a circling aircraft 900 ft below and 3 NM north. Since I was less than 10 NM from ZZZ; I was monitoring unicom radio frequency. I then observed the cessna-182RG approach me nearly head on several hundred feet below and turning into me to pass directly below which I took as an aggressively hostile maneuver. I was certain that he had me in sight. My primary concern was to maintain safe separation to avoid collision; so I maneuvered to gain position above; behind and inside the cessna's turn. At first; I assumed the pilot was curious to investigate the unusual appearance of a glider in the air (although ZZZ is a designated glider field); however; it soon became clear by his tight climbing turns and reversals that the pilot was attempting to engage me in a dog fight. Since I did not know the pilot or his intentions or skills; plus the fact that we were not in radio contact. I re-started my engine and maneuvered defensively to keep him in sight while maintaining lateral and altitude separation. When he passed below in the opposite direction; I took advantage to disengage from the situation by leveling my wings at full power and lowering the nose to accelerate to 125 KTS. My traffic detector; however; indicated that the cessna was closing behind and below; outside my vision. There was now no doubt in my mind that the cessna pilot was flying in an overtly aggressive and threatening manner. My only recourse then was to turn to regain visual contact with him; which resulted in a repeat of the pattern of our initial encounter to gain a defensive position above and behind him. Again I attempted to break off the engagement by heading north and climbing. So it went again several times with the same sequence of being chased and turning defensively to regain visual contact. On the last engagement when I was in a quarter mile tail chase position behind him; I saw him open his left side window and put his arm out; so I closed in off to the side; maintaining safe separation; to find out what he was trying to communicate; but he only continued to wave violently. By then I had good reason to be truly concerned for my safety; so as a last resort option I was able to disengage by climbing into a cloud and turning east. After several minutes of 'cloud canyon flying;' I was hopeful that I had shaken this deranged pilot off my tail and I returned to soaring without further incident.

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Original NASA ASRS Text

Title: Powered Glider pilot reports NMAC with Cessna.

Narrative: I departed ZZZ Airport and turned west. I was soaring engine off in thermal lift at 3;000 feet when my traffic detector alerted me to a circling aircraft 900 FT below and 3 NM north. Since I was less than 10 NM from ZZZ; I was monitoring UNICOM radio frequency. I then observed the Cessna-182RG approach me nearly head on several hundred feet below and turning into me to pass directly below which I took as an aggressively hostile maneuver. I was certain that he had me in sight. My primary concern was to maintain safe separation to avoid collision; so I maneuvered to gain position above; behind and inside the Cessna's turn. At first; I assumed the pilot was curious to investigate the unusual appearance of a glider in the air (although ZZZ is a designated glider field); however; it soon became clear by his tight climbing turns and reversals that the pilot was attempting to engage me in a dog fight. Since I did not know the pilot or his intentions or skills; plus the fact that we were not in radio contact. I re-started my engine and maneuvered defensively to keep him in sight while maintaining lateral and altitude separation. When he passed below in the opposite direction; I took advantage to disengage from the situation by leveling my wings at full power and lowering the nose to accelerate to 125 KTS. My traffic detector; however; indicated that the Cessna was closing behind and below; outside my vision. There was now no doubt in my mind that the Cessna pilot was flying in an overtly aggressive and threatening manner. My only recourse then was to turn to regain visual contact with him; which resulted in a repeat of the pattern of our initial encounter to gain a defensive position above and behind him. Again I attempted to break off the engagement by heading north and climbing. So it went again several times with the same sequence of being chased and turning defensively to regain visual contact. On the last engagement when I was in a quarter mile tail chase position behind him; I saw him open his left side window and put his arm out; so I closed in off to the side; maintaining safe separation; to find out what he was trying to communicate; but he only continued to wave violently. By then I had good reason to be truly concerned for my safety; so as a last resort option I was able to disengage by climbing into a cloud and turning east. After several minutes of 'cloud canyon flying;' I was hopeful that I had shaken this deranged pilot off my tail and I returned to soaring without further incident.

Data retrieved from NASA's ASRS site as of April 2012 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.