Accident Narrative
According to the pilot of the accident airplane, while on the downwind leg of the traffic pattern, he heard a helicopter announce over the UNICOM frequency that it was "inbound...5 miles to the northeast." The pilot continued in the pattern. On final approach at an altitude of 100 feet, he obtained visual contact with the helicopter, which was descending toward the taxiway adjacent to runway 30, about one-third down the runway.
The pilot then decided to initiate a go-around. However, the airplane had already "lost its lift," and only climbed to about 20–30 feet before it was blown "by the propwash of the helicopter" to the left of the runway. The right wing dropped, impacted the runway, and the airplane "cartwheeled," coming to rest on the grassy area between the runway and the taxiway.
Wake Turbulence Guidance
A review of FAA Advisory Circular (AC) 90-23E, Wake Turbulence, revealed: "A hovering helicopter generates a downwash from its main rotor(s) similar to the 'prop wash' of a conventional aircraft. However, in forward flight, this energy is transformed into a pair of strong, high-speed trailing vortices similar to wing-tip vortices of larger fixed-wing aircraft. Pilots should avoid helicopter vortices since helicopter forward flight airspeeds are often very low which generate exceptionally strong wake turbulence."