A federal appeals court ruled yesterday that a woman employed in 1981 as an air traffic controller in Leesburg was the victim of sexual harassment because she was forced to endure "extremely vulgar and offensive sexually related epithets" as a condition of her employment.

The decision, by a three-judge panel of the 4th Circuit Court of Appeals, said evidence at a three-day trial in Alexandria last year showed the Leesburg air traffic control center "was pervaded with sexual slur, insult and innuendo" directed against women.

At the trial last year, District Judge James C. Cacheris denied the claim by the former controller, Deborah Ann Katz, on grounds she had failed to prove that any atmosphere of harassment on the job was intentional. In her appeal, Katz contended federal law does not require a showing of intent and that Cacheris had misread the section of the Civil Rights Act dealing with sexual discrimination.

The appeals court, which apparently agreed, noted the slurs took place with the knowledge of officials of the Federal Aviation Administration, which runs the center.

Lawyers said the decision, written by Judge Sam Ervin III, apparently is the first by a federal appellate court to hold that a stated policy against sexual harassment, such as the one in force at the FAA, is insufficient for an employer to avoid liability.

"It wasn't enough that they had a policy to stop harassment ; they had to stop it," said Barry Gottlieb, a Washington lawyer involved in a successful 1981 sex discrimination challenge against the D.C. Department of Corrections.

George M. Chuzi, Katz's lawyer, said yesterday the appellate ruling shows, "There's a limit to how men treat women on the job. By consistently subjecting a woman to abusive language, you make her acceptance of that language a term of her employment."

The decision said "no significant effort was made to stop the harassment" and that the FAA's policy "was not effective and was known not to be effective by FAA supervisory personnel."

The appeals panel upheld a separate finding by Cacheris that Katz had failed to prove she was denied a transfer because of sex discrimination.

Katz joined the FAA as a controller trainee in 1974 and was certified as fully qualified in August 1980. She was fired in the fall of 1981 for allegedly participating in the illegal air controllers' strike. Chuzi said Katz, now an employe of the National Weather Service, is seeking to get her FAA job back.

The Richmond appeals court returned the case to Alexandria for "consideration of remedies." Chuzi said that what the woman is able to receive as a result of the decision may depend on whether she is rehired.

According to Katz's appeal, she was the only woman assigned to a section of Leesburg controllers from 1977 to 1981. During that time, she alleged, she was subjected to verbal and written sexual advances and slurs. One note from a male colleague said: "Deb, we'll have to get together on your measurements," according to the appeal.

Male controllers also remarked that "a woman does not belong in air traffic; they cannot do the job; they can't handle the stress" and that women are "too emotional; too high strung," Katz alleged.

Katz also maintained she routinely was the target of explicit sexual insults. "The words used were ones widely recognized as not only improper but as intensely degrading," the Circuit Court ruling said. Although she complained about the language to her crew supervisor, John J. Sullivan, the higher court said, " . . . her employer's supervisory personnel did nothing effectual to stop it, and indeed, in Sullivan's case, took part in it."

In a criticism of Cacheris, who became a federal judge in December 1981, the appeals court said it was "hampered" in its review of the case because Cacheris issued no written decision. The judge's oral decision, said the appellate panel, was "exceedingly laconic."