On June 5, 2000, at 1600 hours Pacific daylight time, a Schweizer 269C-1, N2029H, was substantially damaged when the pilot lost control of the helicopter during a practice quick-stop maneuver and impacted the ground near Brentwood, California. The student pilot, the sole occupant, was not injured. The instructional flight was operated by Helicopter Adventures, Inc., of Concord, California, under 14 CFR Part 91. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed from Concord about 1430. The pilot reported that, during one quick-stop maneuver, the helicopter was nearly stopped in a high hover and he was descending to low hover when the helicopter started vibrating and yawed to the left. The controls became ineffective and the helicopter started spinning around until it impacted the ground and then rolled on its side. The pilot's flight instructor said the student told him he performed the quick stop at 30 feet agl. The helicopter was examined in the impound facility on June 19, 2000. The flight control linkage was intact except for one fractured blade pitch control link rod end fitting and the anti-torque push-pull tube at the fuselage/tail boom juncture. The fracture surfaces of both components exhibited a uniform, shiny, metallic appearance. The main rotor blades exhibited modest leading edge damage, modest chordwise striations, and approximately 20 degrees of uniform root-to-tip upward bending deformation. One tail rotor blade was undamaged and the other was bent about 10 degrees tip-inboard at the midspan. The main and tail rotor transmissions turned freely and smoothly when rotated by hand and the magnetic plugs were free of debris. The engine was started (with the transmission disconnected) and ran smoothly at 2,600 rpm for about 5 minutes. The magneto check was normal and engine instrument indications were within normal limits.