The Montgomery County Board of Appeals will hear a request today to clear the way for the second rooftop helicopter landing pad in the county, a proposal that is being strongly opposed by homeowners in the surrounding area.

A private "helistop" proposed for the top of the new, 16-story Clark Building at Wisconsin Avenue and Old Georgetown Road would "jeopardize literally hundreds, if not thousands of people" living nearby, said John D. Whitler, a representative of the East Bethesda Citizens Association.

Clark Enterprises Inc., the country's seventh largest construction company with 3,000 employes, is seeking a special exception that would enable its chief operating officer, millionaire developer James Clark, to commute to Bethesda from his Easton, Md., home.

The helicopter would also be used to ferry Clark and other corporate officials to construction sites in the area, according to Robert H. Metz, a lawyer representing the firm.

The board of appeals has scheduled a hearing for 9 a.m. today in Rockville and will render its decision within a month.

Helistops have been permitted in the county since the late 1960s, but only one was installed, on the roof of the Grammax Office Building off Georgia Avenue in the main Silver Spring business area. Until last November, when the regulations were changed, the landing pads were banned in high-density central business districts such as Bethesda's, said Joe Davis, principal planning and zoning analyst for the Maryland-National Capital Park and Planning Commission.

No other proposals for helistops have been made since the regulation was changed, officials said.

Last week, the Montgomery County Planning Board held a hearing on the Bethesda proposal, and voted 3 to 2 to recommend approval to the board of appeals, which has final say over special exception requests.

The planning board, however, imposed several conditions: One requires that a multiengine helicopter be used in case an engine fails. Another requires that the chopper fly only over major highway arteries that already diffuse high-level traffic noises.

The Bethesda residents point out, however, that there are three schools within several blocks of the Clark Building, and contend that the playing fields of those schools would become the most likely landing spots if a helicopter develops trouble.

"We've heard that the chances of a helicopter having to make a forced landing are low, but should an accident occur, the stakes would be very high," said Frank S. Levy, a representative of the Battery Park Citizens Association.

However, Metz said that measures to ensure safety and minimal noise levels comply with Federal Aviation Administration and county helistop regulations.

The company has proposed three incoming and three outgoing flights on weekdays, between 7 a.m. and 6 p.m. The chopper's flight pattern, which still needs federal and county approval, would follow the Capital Beltway and Wisconsin Avenue at an altitude of about 1,000 feet before entering Bethesda's business district.

The Bethesda Naval Medical Center, located north of the business district on Rockville Pike, lies within the chopper's proposed flight path and also opposes the zoning plan. Cmdr. James Smith, a Navy spokesman, testified that a helicopter could pose a threat to the 7,000 to 8,000 staff members and patients at the sprawling, 243-acre center.

Helicopters may land at the center, Smith said, but only for medical emergencies or at the request of the president of the United States.