It took 47 years to revive Vanity Fair, but only three issues to fire the reviver.

Editor-in-chief Richard Locke was ousted yesterday from the top spot at Conde' Nast Publications' lavish new monthly and replaced by Leo Lerman, veteran features editor of Vogue.

After an 18-month promotion costing about $10 million, the modish journal last seen in 1936 was launched in March to generally unfavorable reviews. Many critics found the articles uneven, the layout perplexing and the overall identity confused. Two subsequent issues, with less advertising, failed to alter the image.

"I was asked to take it in hand and make it the real Vanity Fair," an ebullient Lerman said yesterday from New York, "to make it into a really rousing, witty, intellectual magazine." He could not say what this mandate will mean in terms of changes in the editorial content, since he only learned of the decision yesterday, although "we'd been talking about it for a few days." Nor would he predict any staff changes: "I have to go meet them all first." The prognosis for the present masthead is uncertain, since each of the editors was handpicked by Locke, erstwhile deputy editor of The New York Times Book Review and president of the National Book Critics Circle. Locke could not be reached for comment yesterday.

Lerman, a former writer and book reviewer who says he is in his "late sixties," is the author of biographies of Leonardo da Vinci and Michelangelo and a history of the Metropolitan Museum. He first began contributing to Vogue in 1942, and has been features editor for 11 years. ("I don't have one of those black furs, though.") The fashion monthly is not widely regarded as one of the nation's paramount intellectual journals, and one longtime publishing observer yesterday said of Lerman's appointment, "It's like naming Liz Smith editor-in-chief of the New York Daily News."

But for Lerman, it's the culmination of a 50-year dream. "When I was 14 or 15, a friend once asked me what I wanted to be. And I said, 'editor of Vanity Fair.' " Later, as features editor at Vogue, he found himself presiding over the section of the magazine labeled "incorporating Vanity Fair." And, Lerman said, "I told myself, 'By God, I've at least become editor of the remains!' " CAPTION: Picture, Richard Locke; Copyright (c) 1983, Conde Nast Publications Inc.