THE PLT OF A C150 ENCOUNTERED HAZARDOUS WAKE PRODUCED BY A DEPARTING HELI AT A NON TWR ARPT. WAKE ENCOUNTER. WAKE TURB.

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DURING NORMAL LNDG IN CESSNA 150; IN FINE WX CONDITIONS; A HELI ABEAM OF MY RWY TOUCHDOWN POINT; APPROX 50 FT FROM RWY ON ADJACENT TXWY; LIFTED OFF GND INTO HOVER. I WAS WITHIN 5 FT OF TOUCHDOWN WHEN HE LIFTED OFF. I TRIED TO ADD PWR TO LAND LONG; PAST HELI. SUDDENLY; MY CESSNA WAS HIT BY ROTOR AIR BLAST TURNING ME ALMOST 90 DEGS TO LNDG DIRECTION AND LIFTING WING SO OPPOSITE WINGTIP ALMOST HIT GND. I ADDED FULL PWR; PULLED UP NOSE TO LUCKILY CLR HANGARS NOW IN FRONT OF ME. MANAGED TO RECOVER AND DID NOT HIT BUILDINGS. THIS IS UNCTLED ARPT. FIXED WING PLTS ANNOUNCE ALL TURNS FOR LNDGS. HELI WAS FACING AWAY FROM RWY AS HE LIFTED OFF AND COULD NOT SEE LNDG TFC. HELI DID NOT REALIZE EFFECT OF ROTOR AIR BLAST ON LIGHT ACFT AND WAS TOO CLOSE TO RWY; AND DID NOT PAY ATTN TO CTAF LNDG COMS. RECOMMENDATION -- CAUTION HELI PLTS ABOUT EFFECTS ON LIGHT ACFT. ESTABLISH RIGHT-OF-WAY FOR LNDG LIGHT ACFT SO HELIS WILL NOT HOVER CLOSE AS ACFT IS LNDG. KEEP HELIS AT SAFE DISTANCE FROM RWYS. TELL LAW ENFORCEMENT HELI PLTS NOT TO BE SO ARROGANT WHEN THEIR ACTIONS ARE POINTED OUT. I AM LUCKY TO BE ALIVE AND OWE CREDIT TO MANY HRS OF UNUSUAL ATTITUDE TRAINING GIVEN BY MY PVT INSTRUCTOR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR BELIEVES THAT HELIS WERE NOT 'ON;' EVEN THOUGH IT WAS PAST SUNSET AND THE RWY LIGHTS HAD BEEN ACTIVATED. HE IS ALSO CERTAIN THAT HIS RADIO XMISSIONS WERE NOT HEARD BY THE HELI PLT. WHILE RECOVERING THE ACFT; RPTR WAS UNCERTAIN IF HE PASSED OVER OR NEXT TO THE HELI -- HE WAS FOCUSED UPON THE BUILDINGS; WHICH HE BARELY MISSED BY A FEW FEET. THE ERRATIC PATH OF HIS C150; HOWEVER; RECEIVED CURT VERBAL RECOGNITION BY THE HELI PLT; WHO DIDN'T RESPOND AFTER THE RPTR EXCLAIMED 'YOUR DOWNWASH TURNED MY ACFT.' RPTR BELIEVES THAT THE HELI MAY HAVE BEEN A HU50.