The Federal Aviation Administration conceded yesterday that concern for the appearance of Dulles International Airport influenced its decision to replace a troublemaking radar antenna dome atop the Dulles tower with second-hand equipment.

William E. Broadwater of the FAA's air traffic service, said at a press conference that the dome that will be installed at Dulles next month "won't be the top of the state of the art." Instead it will be an old dome presently installed at Andrews Air Force Base. It has the virtue of looking like the present dome at Dulles.

The top of the state of the art, a newly designed dome that has not been installed anywhere yet, will go to Andrews. It has been described as resembling an upside-down cup and saucer, a coolie hat or a pagoda.

A committee of air traffic controllers charged in a meeting with The Washington Post Wednesday night that the FHA was letting esthetic considerations get in the way of safety. The present radar dome causes the ground radar to be unreliable in wet weather, the controllers charged.

They also charged that a collision of two jetliners on the Dulles runway was narrowly averted Jan. 17 when the radar had failed to operate properly.

Broadwater said at his press conference yesterday that "no hazardous situation occurred as reported in the article this morning."

He said he based that judgment on an interview Dulles officials conducted yesterday with the air traffic controller involved. Air traffic control tapes, which could be played back to determine exactly what happened, are routinely erased after 15 days unless an incident is specifically reported.

Broadwater said that one jetliner, Soviet Aeroflot Flight 318, did proceed to the wrong runway at Dulles. He was "observed" on the ground radar by the controller. Broadwater said.

The crew of United Airlines Flight 738, inbound to the same runway now occupied by the Aeroflot liner, was advised to expect possible "go around" instructions, Broadwater said. Ultimately the United flight was asked to break off the landing approach and circle the field for another try.

The significant differences between the controllers' committee story and the FAA story are questions of whether the radar worked properly and how close the planes came to each other. The controllers said it did not work: the FAA said it did. The controllers described the situation as a "near collision, like Tenerife," the FAA said there was no hazard. The world's worst air disaster occurred on the fogbound runway in Tenerife, Canary Island, last March 27. Two jumbo jets collided on the ground. The death toll has reached 582.

There was no ground radar at Tenerife. Dulles is one of only 12 airports in the United States equipped with ground radar, which shows movements of planes and vehicles on the runways and taxiways.

Ground radar equipment has always been subject to difficulties in wet weather, Broadwater said. Sheets of rain, collecting on the dome, distort or create "blind spots" in the radar picture, he said.

The latest dome design is supposed to resolve that problem. But it does look different and Dulles Airport, praised as an architectural masterpiece, has legions of protectors.

An FAA spokesman said yesterday that the decision to use the similar-looking but more rigid Andrews dome instead of the new design was made last June by William M. Flener, associate FAA administrator for air traffic and airway facilities, and James T. Murphy, director of Metropolitan Washington Airports, the FAA agency that runs Dulles and Washington National airports.

The latest design, the spokesman said, "couldn't improve the radar cover that much to justify what we would expect to be a hue and cry" about changing Dulles' appearance. Properly functioning ground radar, Broadwater said, is not regarded as a "go or no-go item." That means it doesn't matter whether the radar works or not.

But when the spokesman was asked if airports ever operated in low-visibility situations only because they had a ground radar, the spokesman said. "It depends on the situation. There is no hard and fast rule."