A SIGHTSEEING HELICOPTER dropped about 800 feet into New York's East River when its engine conked out, but all five people on board were unharmed. . . . A MAN ARMED with a hand grenade who hijacked an Air Algeria plane on a domestic Algerian flight gave up to authorities Monday after holding the plane's passengers and crew hostage for several hours. . . . NEW ZEALAND'S conservative government cut welfare and sickness benefits by up to a quarter Monday, saying the unemployed must be coaxed back to work.