None of the potential sites for a new National Airport control tower will allow full view of all runways and solve other design flaws, and the problem could delay work on National's new terminal by up to a year, airport authority officials were told yesterday.

Officials acknowledged that there will be no easy, quick or cheap solution to the obstacles posed by the planned main terminal at National. As currently designed, the terminal would block the air traffic controllers' view of one runway from the existing control tower.

After being briefed by designers, the Metropolitan Washington Airports Authority's Planning Committee voted formally yesterday to build a new tower, even though site selection and approval could take more than a year, and no tower site currently identified was described as acceptable.

The action ruled out the option of moving the planned $200 million terminal, now slated to open in 1994, largely because of the extreme cost and delays. Design problems were cited in rejecting the alternatives of changing the terminal's design at its approved location or moving a taxiway.

"There is no one site that solves all the problems," said Mark Shoemaker, of the architectural firm of Cesar Pelli & Associates, which designed the new terminal.

The delay in choosing and approving a tower site "is going to set back the whole schedule" for renovations at National, lamented board member Polly Shackleton.

The authority's general manager, James A. Wilding, said the terminal construction plan "is still in its early stages" and that some of the delay could be reduced once a consensus is reached on a tower site. He said new control towers generally cost close to $10 million.

The action occurred under the shadow of a federal appeals court decision that part of the law giving the agency control of National and Dulles International airports is unconstitutional. That decision has been stayed pending a Supreme Court appeal, and agency officials say they doubt that their actions will be invalidated because they are acting in good faith and are performing essential functions.

If the airport authority had decided to move the planned terminal, its opening could have been delayed two to three years, and its cost could have risen by up to $100 million, officials said.

Authority member T. Eugene Smith voted against a new tower yesterday, saying, "My intuition tells me there's something more we can do." He suggested putting a key part of the new terminal partly underground so that the air-traffic controllers' view from the current tower could be maintained.

Officials say most of the choices that would avoid moving the terminal or the control tower would still reduce the terminal ceiling height from the planned 20 feet to less than 12 feet, which airlines generally oppose.

Two of the five potential tower sites described by consultants and authority board members yesterday as the most promising are along the Potomac River. Those locations pose the greatest danger of the tower being struck by aircraft, board members were told, and the sites could raise objections by federal planners that either would mar views along the shoreline and monument areas.

Three other tower sites under consideration -- one on the roof of the new terminal and two atop new parking garages -- would require towers 200 to 300 feet high, and would force changes in the plans for the terminal, garages and nearby roads, officials and consultants said.

The current tower rises less than 80 feet above sea level. The proposed riverfront sites are for towers of 101 and 169 feet; a tower atop the center of the new terminal would rise 207 feet; and sites atop parking garages to be built west of the Metrorail station could warrant a tower as high as 300 feet, according to estimates presented to authority members yesterday.

Planning Committee Chairman Carrington Williams said he wished that one possible tower location "would just jump out" as the obvious choice and shorten the process. Added Williams, "My main concern is that we do it right."

Approval for the tower is needed from the Federal Aviation Administration. An FAA spokesman said the one-year estimate for approval is "pretty realistic." The $735 million set for the renovation of National does not include the expense of the new tower or related costs, officials say.