NTSB Factual Report

On July 16, 2016, about 1315 eastern daylight time, a Schweizer 269C-1, N6148D, was substantially damaged after it experienced ground resonance while on a taxiway at the Tom B David Field Airport (CZL), Calhoun, Georgia. The commercial pilot and a commercial pilot rated passenger were not injured. The helicopter was registered to and operated by R & B Helicopters, Inc., under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and no flight plan was filed. The local flight originated about 15 minutes earlier from CZL.

The commercial pilot, who was seated in the right seat stated that because he had not previously flown the accident make and model helicopter before, the owner took him for a demonstration flight and executed several full touchdown autorotations. After concluding that flight, the owner exited the helicopter and a commercial rated pilot who was a friend of the owner, and the commercial pilot boarded the left seat of the helicopter. The helicopter subsequently departed and while in the vicinity of the airport, the left seat pilot flew the helicopter briefly. After about 10 to 15 minutes, the right seat pilot landed the helicopter uneventfully on a taxiway and remained there between 30 seconds and 1 minute with the engine at idle, while they discussed the differences between a helicopter that was equipped with a correlator and a helicopter that was equipped with a governor to maintain rpm, which they intended to operationally test. The right seat pilot guarded the collective in the down position with his hand and slowly applied throttle. As the rpm increased he reported feeling a shake, then a "boom boom" sound and noticed a vibration, which he identified from training as ground resonance. He reduced throttle but the vibration increased. At that time the left seat pilot advised him to pick the helicopter off the ground, and attempted to assist by raising the collective. The throttle was advanced and with the rpm near the green arc the helicopter began shaking and did not become airborne, although the collective was raised. The main rotor blades contacted the tailboom several times and the right seat pilot attempted to locate the rotor brake, and then turned off the ignition switch.