"The only fear," George Willig explained today after electrifying th city by scaling one of the two 1,350-foot World Trade Center towers, "was at the beginning. It was a fear of getting stopped before I got anywhere."

Tp Willig, 28, a mountain climber from Queens, the thousands cheering in the streets below didn't matter, and the police imploring him to seek safely didn't matter.

"I finally did something I've been planning for a year and was very, very satisfied with it," he told reporters once he was back on the ground.

Willig, using complicated equipment he had designed specifically for this climb, began to scale the sheer aluminum face of the quarter-mile tall tower about 6 a.m. Three and half hours late the highest peak of the city's steel and concrete canyons had been conquered and a year-long dream realized.

To Willig, the vertical ascent was more crusade than stunt. Once he reached the top and had crawled seat first through a small window where he was met by the police, he proclaimed his motivation for the climb in classic mountaineering terms:

"Because it's there."

Before the police whisked him away, Willig, a toy designer employed by the Ideal Toy Corp., said that as mountains go, the World Trade Center was "just another climb."

Willig was nonchalant almost to the point of insouciance during his perilous climb, according to two police officers who accompanied him for about half the trip. They had been lowered down from the roof about 8 a.m. in a bucket-liked, enclosed platform used for window-washing and maintenance work.

They said that Willig rejected their pleas that he join them on the platform, explanining that he felt "safer" where he was.

On the way up he joked, and frequently rested in a harness, letting his arms and legs dangle freely.

At the 75th floor he paused long enough to nibble delicately at a doughnut and to give his autograph - inscribed "to my co-ascenders" - to each of the two officers.

Willig was charged with disorderly conduct, reckless endangerment, criminal trespass and climbing a building without a permit. He was allow ed to go hime without having to appear before a judge.

Four persons who accompained him to the building but who remained on the ground were also arrested, charged with acting in concert with the wiry bachelor.

In addition, the corporation counsel, Bernard Richland, said the city would file a civil suit against Willig to recover costs incurred by diverting men and equipment to the World Trade Center. "There's no reason," Richland said, "why we should continue to be victimized by this kind of foolishness. It's about time something was done to make people pay for their amusements."

Willig's caper marks the third time that a daredevil had selected the World Trade Center as a prob.

On Aug. 7, 1974, Phillip Petit, a Parisian aerialist, stretched a tightrope between the two towers and cavorted back and forth on it for 30 minutes before decidind to call it a day. When he got down he explained that it was "themost beautiful place in the world to walk."

On July 22, 1975, the Center, whose twin towers are the second-highest building in the country, 100 feet lower than the Sears Building in Chicago, were picked as a nice place for a sky dive by Owen Quinn.

In today's adventure Willig used a standard mountaineering harnass, but added special grips he had spent a year designing.

On the northeast side of the building, where he climbed, there are half-inch wide, C-shaped vertical grooves spaced 40 inches apart. They are tracks for a machine used to wash that portion of the building. Willig designed his grips to fit inside th ese grooves. He could manipulate them so that they expanded like a brake shoe when he wanted to lock them in to place, and he then used them in much the same way a conventional climber uses pitons - mountain-climbing hooks.

Willig's father, also named George, said his son, a graduate of St. John's university who majored in environmental studies, had told him yesterday that today was to be the day of the climb. Asked if he tried to dissuade his son, He replied: "He's 28, what do you say to someone who's 28?"

During the climb police placed a 20-foot square, six-foot high air cushion directly below Willig. Despite the lack of predictability of his landing spot, had he fallen.

DeWitt Allen, one of the officers who accompained Willig on his spider-like trek, said that Willig five or six times encountered grooves that were bent out of shape.

Each time, he said, Willig calmly paused, took a hammer out ofthe knapsack on his back, and pounded the grooves back into shape. "I don't think he was in danger at any point, "Allen said. Glen Kildare, Allen's partner on the platform, admitted afterward that he may not have been the ideal man for the job. "I'm afraid of heights," he said.

As he left the police station after being booked, Willig, surrounded by a crush of reporters, put the day's event in his own very special person.