Luscombe 8A pilot reported loss of directional control on landing roll after encountering rotor wash from a helicopter operating near the runway.

Narrative

Upon entering the pattern on downwind to Runway 09 (winds 090 at 5 MPH); I made contact with the pilot of a Bell 505 helicopter who was giving dual instruction. The helicopter was hovering very near the intersection of Runway 09-27 (asphalt) and Runway 17-35 (Turf). By the time I was abeam the numbers (09) the helicopter had positioned itself approximately 50-75 feet south of Runway 09 while hovering over the centerline of Runway 35-17. Turning off of the abeam; I noticed that the aircraft was clear of Runway 09-27; but still fairly close to the southern edge of the asphalt. I slowed to final approach speed in the descending turn and landed close to the numbers as possible in order to make the first turn off. I wheel landed the aircraft on centerline and the tail-wheel had not yet contacted the runway surface. The landing and subsequent rollout were uneventful (winds 090-5MPH) - but after traveling approximately 700 FT the aircraft abruptly lurched to the left. Full right rudder and right braking with full left stick did not remedy the out-of-control travel to the left side of the 80FT wide runway. The aircraft came to rest at the edge of the runway (approximately 750 feet from the threshold) after having rotated left approximately 110 degrees in a ground loop that damaged the right wheel and wheel pant; and damaged the right wingtip that had contacted the ground in the tight turn. I shut down the engine and pushed the aircraft clear of the runway. I believe that the wake turbulence and rotor downwash from the helicopter that was hovering UPWIND of my chosen landing location was the key contributing factor in this incident. I should have elected to land on Runway 27 to completely avoid any exposure to the wake generated by the helicopter. Even with a slight tailwind; the 5000 ft runway would have afforded me ample space to safely land and avoid any ground turbulence contact. Having been segregated most of my professional and personal aviation career from working in close proximity to rotary wing aircraft---I was astonished at the level of turbulence generated by this relatively small aircraft. Additionally; I do not think the pilot of the helicopter realized that ground handling characteristics of tail-wheel (conventional gear) aircraft are MUCH more sensitive than that of nose gear aircraft.