EXPERIMENTAL ACFT PILOT REPORTS NMAC WITH HELICOPTER ON SHORT FINAL.

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FOLLOWING A SHORT VFR TEST FLT; I BEGAN ENTRY INTO THE VFR TFC PATTERN AT ZZZ. CONDITIONS WERE CLR UNLIMITED VISIBILITY WITH LIGHT WINDS FAVORING RWY XX. I ENTERED THE NORMAL L-HAND TFC PATTERN AT PATTERN ALT ON THE UPWIND LEG. PROGRESSING THROUGH THE PATTERN; I MADE 4 TA'S ON THE CTAF OF 122.8. THERE WERE NO OTHER ADVISORIES HEARD ON THE FREQ OR OTHER ACFT SEEN WHEN SEARCHING THE LCL AREA. I WAS ALSO MONITORING THE APCH CTL FREQ AND DID HEAR AT LEAST 1 ATTEMPT BY THEM TO CONTACT A HELI APPARENTLY TRYING TO DISCONTINUE RADAR SVC. THERE WAS NO RESPONSE HEARD FROM THE HELI AND NO LOCATION WAS NOTED. ON SHORT FINAL APCH AT ABOUT 1/2 MI FROM THE END OF THE RWY AND APPROX 400 FT AGL; THE FBO ATTENDANT BROADCAST; 'DO YOU SEE THE HELI?' I RESPONDED 'NO; WHERE?' THE ATTENDANT CORRECTLY IDENTED THE LOCATION 'OFF YOUR R WING.' AT THIS POINT; I OBSERVED THE HELI EMERGE FROM THE BLIND AREA BELOW MY R WING FLYING R TO L ACROSS THE APCH END OF THE RWY AT APPROX 100 FT AGL. I TOOK EVASIVE ACTION INITIATING A CLBING R TURN TO AVOID THE HELI AND ABORTING THE LNDG APCH. AFTER LNDG; IN DISCUSSIONS WITH THE HELI PLT; HE ACKNOWLEDGED NOT BEING ON THE CTAF; NOT MAKING ANY TA'S AND APOLOGIZED FOR HIS ACTIONS. SEVERAL GND WITNESSES OBSERVED THE HELI FLYING AT HIGH SPD AND LOW ALT WBOUND NEAR THE ARPT SOUTHERN BOUNDARY AND MAKING A RAPID TURN OVER THE ARPT BOUNDARY AND PROCEEDING DIRECTLY TO A RAMP ON THE W SIDE OF THE ARPT. I CREDIT THE ALERT RESPONSE OF THE FBO ATTENDANT WITH THE PREVENTION OF A POSSIBLE MIDAIR COLLISION.