A U.S. District Court judge here told the federal government yesterday to pay Betty V. Cayce, a retired employee of the Federal Aviation Administration, more than $11,000 because, the judge found, she was paid less - because of her sex - than a man doing the same work.

Judge Gerhard A. Gesell said that FAA job classifiers had determined that Cayce was being paid at the proper pay scale for the the work. But, since a man doing similar work was being paid more because of his sex, Cayce had a right to recovery under the federal Wqual Pay Act.

In a footnote to his opinion, Gesell said that when such a misclassification is found, the "proper course" would be to immediately downgrade the man's pay level to meet the proper salary level - rather than upgrade the woman's.

Gesell considered . . . and rejected . . . arguments that the woman's pay should have been increased to meet the man's salary level.

"It simply cannot be maintained that Congress intended to remedy every sex-based civil service misclassification by upgrading all those with the lower grade even when, as here, the classification standards indicate that the lower grade is the correct one," the judge said.

"Such a practice would result in widespread grade inflation and thus threaten the integrity of the entire civil service system," Gesell said.

Gesell's decision was the first time a court had ruled on the application of the Equal Pay Act to the Civil Service Commision's job-classification system, attorneys in the case said.

The act prohibits discrimination between federal employees on the basis of sex. The question in the Cayne case was whether the classification system, as applied to her case, benefited her coworker because he is male.

The court found that Cayce, a statistical assistant, and her male coworker "were performing equal work on jobs requiring equal skill, effort and responsibility, under similar working conditions," from early 1974 until Cayce retired from the FAA in December of last year.

Cayce however, was paid at a Grade 8 level while the man was paid as at Grade 11, the opinion said.

Cayce's male supervisor, knowing her-work was equal to her male counterpart's sought promotions for her to a higher pay scale, but FAA job classifiers, all of whom were female, "proceeded by the book" and "concluded she was entitled to a GS-8 and nothing more," Gesell said.

Gesell found, however, that prior to August, 1975, the job classifiers did not know that the man was doing the same work as Cayce.

"The classification system operated imperfectly in allowing the unjustified disparity in pay, but the imperfection was in no way sex-based" up to that point, Gesell said.

After that, Gesell said, when both Cayce's supervisor and FAA job classifiers knew she was not qualified for a promotion, and knowingly failed to reduce the man to Cayce's pay scale, the job classification system was not applied properly.

While Cayce's supervisor was anxious to have her promoted, he was not ready to demote the man who was paid at the higher level, Gesell said.

While neither the supervisor nor the classifiers were shown to have any bias against females, Gesell said, they knowingly failed to correct the situation with Cayce.

Since the differentiation between a lower-paid woman and a higher-paid man doing equal work was shown to be "sex-based," Gesellsaid, Cayce was owed damages under the Equal Pay Act.