"Fun With Dick and Jane," now at area theaters, is a fitfully amusing trifle about an affluent suburban couple, played by George Segal and Jane Fonda, who ultimately become an armed robbery team in order to maintain their srandard of living after he loses a high-paying job in the aerospace industry.

If movie comedies as stale "For Pete's Sake" and "The Silver Streak" can find tolerant and even appreciative audiences, a relatively classy disappointment like "Fun With Dick and Jane" may find some success.

The project evidently began a few years ago as a topical story idea with serious intentions, written soon after the economic crunch had led to extensive cutback at aerospeca firms in Southern California and drastically altered the status of hundreds of well-educated and perhaps over-specialized breadwinners. David Giler, who later wrote and directed "The Black Bird" with George Segal, was engaged to transform the idea into a comedy. He shares finals screenwriting credit with Jerry Belson, best known as the writer of "Smile," and Mordecai Richler, fresh from the movie version of his own novel "The Apprenticeship of Duddy Kravitz," which had been directed by his friend and compatroit, Ted Kotcheff, the director of "Dick and Jane."

Unfortunately, this convergence of comedy talent hasn't produced a satisfying comedy script. Perhaps it was a case to asking too many clever cooks to mess around with the recipe. "Dick and Jane" isn't scathing, and it isn't sympathetic. It's not even consistently glib. The conception remains too indepencive and trivilized to make a distinct impression.

The sudden loss of income and security experienced by Dick and Jane Harper could be the basis of the smart satirical comedy or a smart realistic comedy, but in this case several smart guys seem to have failed to bring either conviction or a unifying point-of view t o the premise. There's precious little social dimension to this story about people desperate to maintain appearances and social status. The vast majority of the situations are kept within narrow, facetious farce boundaries that don't reveal anything in particular about the characters and the class they belong to. "Dick and Jane" is caught in a time wrap, vaguely conscious of social uncertainties and insecurities that emerged in the '70s but webbed to the conventional, inconsequential surburban farce formulas that characterized many successful comedies of the '60s, particularly the Doris Day vehicles.

The Harpers are drawn into crime accidentlly, and it's probably significant that the action seems most agreeable when they flop as stick-up artists. For example, Segal's best slapstick opportunity things he doesn't want from the kindly pharmacist he intended to rob.

The filmmakers fudge the characters' criminality in an interesting way. The pharmacy remains safe, and there are no liquor store or gas station holdups. However, Dick and Jane are allowed to rob a record store, a porno motel, a crooked evanelist and the telephone company, the latter to the cheers of resentful bilpayers who happen to be in the office at the time. The choices indicate a certain strain about determining deserving and underserving targets. One misses the assurances typical of British movie comedies of a generation ago: The criminal schemes of a Dennis Price in "Kind Hearts and Coronets" of an Alastair Sim in "The Green Man" were free of sentimentally, because one understood the class snobberies and grievances motivating them.

The most despicable touch in "Dick and Jane" finds the protagonists trying to avert capture by tossing loot out the car window. As bystanders grovel for the windfall, Dick and Jane are permitted to elude moral responsibility as well as captured. Dick and Jane may be crooks, but so what? Everyone's a greedy pig at heart.

Dick and Jane climax their career by making off a bribery cache hoarded by his ex-boss, played of Ed McMahon. For the purposes of upper-middle-class crime fantasy, it might have been preferable to forget all the justifiable-unjustifiable stickups and concentrate on the big caper motif of entertainments like "The Sting."

The motive's conceptual weaknesses and equivocations make it easier for the transient supporting players like McMahon, Alan Miller as a loan officer, and John Dehner as Jane's complacently well off father to make an impact than the stars, who are compelled to sustain characters that never acquire substance. One can't fault Segal and Fonda for performing like loyal troupers, but one can certainly wish them stronger material.