The pilot of the tailwheel equipped airplane reported that during the landing roll, the airplane veered to the left and exited the runway. The pilot applied right rudder input and increased engine power to raise the tail as he maneuvered the airplane toward the runway surface. As the airplane rolled onto the runway surface, it veered to the right, exited the runway, and continued onto the parallel taxiway. The pilot firmly applied both brakes to avoid a fuel island and the airplane subsequently nosed over, which resulted in substantial damage to both wings and rudder. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. At the time of the accident, the pilot was landing on runway 16, with light and variable wind. The pilot reported that there was a helicopter to the left of the runway on a parallel taxiway and felt that its rotor wash was a factor in the accident.