C172 PLT HAS DIFFICULTY MAINTAINING ALT AND IS EVENTUALLY ASSIGNED BLOCK ALT BY ROA TRACON.

Narrative

I WAS ON A FLT FROM TOCCOA; GA; TO LANCASTER; PA. DEPARTED TOCCOA AT XA05 AND ARRIVED AT MY FUEL STOP; LYNCHBURG; VA; AT XC15. THE FLT WAS IN SMOOTH AIR AT 7000 FT; WITH CAVU CONDITIONS. THERE WAS MILD TURB ON APCH INTO LYNCHBURG WITH GUSTY WINDS. AT LYNCHBURG; I RECEIVED A THOROUGH WX BRIEFING FROM THE FSS SPECIALIST AT FSS. ACCEPTABLE WX CONDITIONS WERE TO CONTINUE WITH GOOD VISIBILITY AND CLR SKIES. MODERATE TURB WAS FORECASTED ALONG THE RTE WITH STRONG WINDS OUT OF THE W. I CALLED THE FBO AT THE DEST ARPT. THEY RPTED THAT THE ARPT WAS ACTIVE AND FLTS WERE BEING CONDUCTED. I FILED FOR AN EASTERLY RTE TO KEEP AS FAR FROM THE MOUNTAINS AS POSSIBLE. THIS CLRNC WAS RECEIVED FROM GND CTL. ON CLBOUT FROM LYNCHBURG; THERE WAS SOME LIGHT CHOP. DURING THIS TIME MY RTE WAS AMENDED TO A MORE NORTHERLY RTE; CLOSER TO THE MOUNTAINS. AT MY ASSIGNED ALT OF 7000 FT MSL; THE AIR WAS SMOOTH; SKY CLR WITH EXCELLENT VISIBILITY. I WAS AWARE OF THE POSSIBILITY OF UP- AND DOWNDRAFTS; AS THEY WERE EXPERIENCED ON THE TRIP TO TOCCOA A FEW DAYS EARLIER. APPROX 15 MI N OF LYNCHBURG; VA; THE PLANE ENCOUNTERED A STRONG DOWNDRAFT. I TOOK IMMEDIATE ACTION TO ARREST THE SINK RATE OF THE PLANE. I REALIZED THAT THE PLANE COULD NOT HOLD ALT. I CALLED ROA DEP CTL AND TOLD THE CTLR MY SIT AND ASKED FOR A BLOCK ALT. I WAS THEN DSNDING THROUGH 6700 FT MSL. THE CTLR SAID THAT HE COULD NOT GIVE ME A BLOCK ALT; BUT THERE WAS NO TFC IN THE AREA. AS THE PLANE CONTINUED TO DSND; CONTINUOUS COM TRANSPIRED BTWN MYSELF AND THE ROA DEP CTLR. HE SUGGESTED I TURN 90 DEGS TO THE E AND TRY TO CLB BACK TO 7000 FT MSL. THE SINK RATE SLOWED AND I SOON WAS ABLE TO HOLD ALT. I HAD ONLY TRAVELED A FEW MI WHEN I ENCOUNTERED A 2000 FPM UPDRAFT. THE CTLR AND I DISCUSSED THE OPTIONS. WE TALKED ABOUT RETURNING TO LYNCHBURG. THEN HE SUGGESTED I TRY 9000 FT ALT IF I ELECTED TO CONTINUE THE FLT. THE PLANE WAS THEN AT 7000 FT MSL AND CLBING AT LEAST 1500 FPM. I ELECTED TO GO TO 9000 FT. AT 9000 FT THE AIR WAS SMOOTH. A BLOCK ALT OF 7000-9000 FT MSL WAS GIVEN BY THE CTLR. WITH CTLR APPROVAL; I TURNED BACK TO THE N AND PROCEEDED TOWARD MY ASSIGNED RTE. THE FLT REMAINED IN CAVU CONDITIONS; SMOOTH AIR AND THE BLOCK ALT WAS REMOVED. THE REMAINDER OF THE TRIP TO LANCASTER WAS UNEVENTFUL.