On February 27, 1999, at 1256 hours Pacific standard time, an Enstrom F-28F, N5700C, rolled over and crashed during takeoff from the Reid-Hillview Airport, San Jose, California. The aircraft sustained substantial damage. The commercial pilot, who holds private helicopter privileges, and the mechanic were not injured. The aircraft was operated as a maintenance test flight by California In Nice Air, Inc., under 14 CFR Part 91 of Federal Aviation Regulations, and was originating when the accident occurred. Visual meteorological conditions prevailed at the time and no flight plan was filed. The pilot stated that he was in the left seat, applying collective in preparation to liftoff from the pad. As he pulled collective, the aircraft suddenly rose vertically to a height of 4 feet agl. He was surprised because he did not feel at the time that the aircraft had become light enough to hover. As the aircraft ascended, the fuselage began a left and right pendular motion, which then shifted to fore and aft movement as he attempted to recover. As the aircraft pitched forward for the final time, the main rotor blades struck the ground. After the rotor blades struck the ground, the aircraft rolled onto its right side before coming to rest. The pilot exited the aircraft without assistance. The mechanic shut off the master and fuel switches before being assisted through the broken windscreen by several nearby witnesses to the accident. The pilot stated that he has about 147.8 hours in helicopters and 110.3 hours in the F-28F, but had not flown the aircraft in the preceding 90 days. He said he thought he might have initially mispositioned the cyclic before raising the collective, but was also attempting to comply with the mechanic's request to "pull-off before vibration became a problem." He did not clearly recall what occurred or what control inputs he made after becoming airborne. He also did not remember making any sudden or abrupt control movements, but said the controls "felt" differently than he had expected. The mechanic had removed the right cyclic and pedal controls prior to flight. The mechanic, who occupied the right seat, reported the flight was being conducted to verify the main rotor tracking and balancing that had been completed earlier. The aircraft had already been test flown once since the tracking and balancing were completed with no reported abnormalities. The mechanic said there were three targets installed on each main rotor blade and a magnetic pickup on the main rotor mast. Also installed at the time was the associated wiring that connected the Strobex and Chadwick test equipment located in the rear of the aircraft. A Federal Aviation Administration airworthiness inspector checked the aircraft flight controls after the accident and reported that there was no evidence of any preexisting mechanical defects.