PIPELINE PATROL PLT FLEW CESSNA 177 CARDINAL THROUGH WAKE TURB A MI BEHIND A DC-9.

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WAS PATROLLING PIPELINE (CLE). TWR CALLED TFC DC-9 LNDG RWY 5R. ONCE TFC IN SIGHT; PROCEEDED WBOUND; PASSING BEHIND DC-9. I DID JUST AS INSTRUCTED. I NOTICED I WOULD BE GOING THROUGH FLT PATH. THEREFORE; I TIGHTENED SEAT BELT BUT DECIDED NOT TO CLB. THIS DECISION MADE BECAUSE NUMEROUS SITS SIMILAR TO THIS; TRANSITIONING MANY CLASS B ARPTS; THE SLIGHTEST BUFFET FROM WAKE TURB HAS NEVER BEEN ENCOUNTERED. HOWEVER; ON THIS DAY WHILE FLYING THROUGH THE FLT PATH ALMOST PERPENDICULARLY WAKE TURB WAS ENCOUNTERED. TURB WAS MODERATE TO SEVERE; NO ROLLING MOTION. ACFT NEVER DEPARTED CTLED FLT. KNOWN WAKE AVOIDANCE PROCS WILL BE IMPLEMENTED TO AVOID WAKE TURB IN FUTURE SITS REQUIRING THAT ACTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING PIPE PATROL ALONE IN A 150 HORSEPWR CESSNA 177 CARDINAL. THE PIPELINE HE WAS PATROLLING IS ABOUT 2 MI S OF CLE ARPT. THE WX IN HIS OWN WORDS WAS MARGINAL VFR 2000 FT OVCST AND 5 MI EXCEPT IN THE SCATTERED SNOW SHOWERS. TEMP WAS ABOUT 28 DEGS AND THE WIND WAS ABOUT 240 DEGS AT 6-8 KTS. HE ESTIMATED HE CROSSED THE PATH OF THE DC-9 ABOUT A MI AT ABOUT A 40 DEG ANGLE. THE RPTR WAS AT ABOUT A 270 DEG HDG AND THE DC-9 WAS AT ABOUT A 230 DEG HDG. THERE WAS NO WARNING OF ANY KIND. FIRST NEGATIVE G'S AND THEN POSITIVE G'S. HE HAD GONE THROUGH THE PATH OF OTHER ACFT IN A SIMILAR FASHION WITH NO PROB IN THE PAST; SO THEREFORE; HE WASN'T CONCERNED. BUT; THIS TIME WAS DIFFERENT. FROM NOW ON HE SAYS HE WILL NEVER GO UNDER THE PATH; BUT RATHER; FOLLOW GOOD OPERATED PRACTICES LIKE FLYING OVER THE WAKE; STAYING UPWIND OF THE WAKE AND BEING ALERT FOR THE POSSIBILITY OF WAKE.