With twin 2,520-horsepower engines and up to 19 seats, the Sikorsky S-92 is among the world's most powerful civilian helicopters. "Helibuses" typically service offshore oil platforms and the like, but two years ago billionaire industrialist Ira Rennert acquired a posh version to shuttle himself between Manhattan and Long Island's exclusive Hamptons, where he owns a 63-acre, 110,000-square-foot villa complex. One of the first to notice the giant bird was Frank Dalene, founder and CEO of a successful luxury homebuilding company, who lives on a ridge along Rennert's flight path. Its whumping rotor was like "a lightning bolt striking nearby," says Dalene, a fast-talking 58-year-old with a long nose and narrow-set eyes. He blames the vibrations for "literally damaging my home."