A U.S. District Court judge is expected today to order Northwest Airlines to pay $52 million in back pay and interest to a group of stewardesses who sued the airline for employment discrimination -- the largest amount ever awarded in such a suit, according to lawyers in the case.

U.S. District Court Chief Judge Aubrey E. Robinson Jr., who has presided over the case since it was first filed in 1970, decided in November 1973 that the airline had discriminated against the stewardesses.

The practices cited by the judge as discriminatory, according to the plaintiffs' attorneys, included paying the women less than men who did comparable work, providing better hotel accommodations for men and imposing more restrictive weight and appearance codes for females than for their male counterparts.

Over the last nine years, protracted appeals by both sides on various aspects of Robinson's original ruling and disputes over determining what amount each stewardess would receive have delayed the final judgment.

Under a formula laid down by Robinson, lawyers for both sides have agreed upon a figure of $52.5 million and Robinson had said earlier that he would award whatever amount was agreed upon.

However, an attorney for the airline said yesterday that the company plans to appeal Robinson's 1973 decision, which only becomes final after the award is granted. Consequently, it will still be some time before the 3,364 stewardesses involved, some of whom stand to get $50,000 each from the company, receive any money.

A portion of the $52.5 million award will accrue nine percent interest while the company appeals, according to lawyer Philip Lacovara, who represented the company.

Michael Gottesman and Penny Clark, attorneys for the stewardesses, said yesterday that the award includes compensation from 1967 to 1976, when male stewards received some $2,000 to $3,000 a year more in pay than female attendants. In 1967, stewardesses were paid about $7,500 a year, while stewards were making about $10,000, Gottesman said.

The company also furnished male attendants with single hotel rooms while female attendants were required to double up, Gottesman and Clark said. In addition, they said the company imposed rigid weight requirements for women but not for men and provided uniform cleaning allowances for men but not for women.

Since Robinson's original ruling, the company has raised the salaries of female flight attendants to equal those of male attendants, no longer has weight requirements, and affords single hotel rooms and uniform cleaning allowances to women attendants.

Between 1974 and 1981, the company offered to reinstate any female attendant who had been fired for not complying with weight requirements.

Lacovara said yesterday that while the compensation calculations had been agreed upon by both sides, the company will appeal, arguing, as it did originally, that there was no discrimination, and that the male attendants -- who were called pursers when the suit was filed -- were performing different tasks than the stewardesses.