TEMPORARY LOSS OF ACFT CTL IN A C152 WHEN IN PROX OF ROTARY WINGED TFC.

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I WAS FLYING WITH A STUDENT IN L CLOSED TFC TO RWY 19L. SEVERAL OTHER AIRPLANES WERE IN THE PATTERN; AS WELL AS A B206 HELI. MY AIRPLANE STUDENT IS A HIGH-TIME B206 PLT AND WE BOTH OBSERVED AND AGREED THAT THE B206 WAS HAVING A TOUGH TIME WITH THEIR CTL ON THEIR APCHS. THE B206 WAS FULL-STOPPING TO A HOVER OVER THE NUMBERS ON RWY 19L ON SEVERAL CIRCUITS AND WAS TAKING QUITE A LONG TIME TO TKOF AFTER EACH APCH AND WAS SLOWING DOWN THE TFC PATTERN AND I BELIEVE THAT SEVERAL AIRPLANES HAD TO GAR BECAUSE THE B206 HADN'T CLRED THE RWY. ON ONE OF OUR FULL-STOP TAXI BACKS WE OBSERVED THE B206 TKOF DOWN RWY 19L AFTER REQUESTING AN 'AIR TAXI' TO THE COMPASS ROSE AT THE END OF RWY 19L. THE HELI FLEW AT ABOUT 100 FT AGL. THEN WE WERE CLRED INTO POS AND HOLD ON RWY 19L AND RIGHT AWAY FOR TKOF FOR L CLOSED TFC. TWR ADVISED US TO MAINTAIN VISUAL SEPARATION ON THE HELI AHEAD BUT DID NOT ADVISE US ABOUT ROTOR-WAKE TURB. AS WE TOOK OFF IN OUR C152; AT ABOUT 50 FT AGL WE EXPERIENCED A 25 DEG UNCOMMANDED R ROLL NEAR THE END OF RWY 19L WHERE THE HELI HAD JUST BEEN. I TOOK THE CTLS AND NEUTRALIZED THE DANGER; WE CONTINUED OUR PATTERN. A COUPLE OF CIRCUITS LATER THE HELI WAS BACK IN THE PATTERN WITH US AND AT ONE POINT TWR CALLED THE HELI TO SCOLD THEM ABOUT MESSING UP THE PATTERN. THE HELI THEN REQUESTED AN AIR TAXI TO THE SE PADS AND WAS CLRED FOR THAT REQUEST. TWR THEN CLRED US TO TKOF AGAIN BEHIND THE HELI. I TOLD MY STUDENT TO HOLD IN POS AND REQUESTED A DELAY FOR 'ROTOR TURB AVOIDANCE.' IT THEN BECAME OBVIOUS THAT TWR WAS UNAWARE OF THE DANGER. ON THE CIRCUITS WHEN THE HELI FLEW A NORMAL PATTERN WE DIDN'T END UP IN PROX TO THE WAKES. THE DANGER SEEMED TO HE RELATED TO THE LONG LOW LEVEL AIR TAXIS.