The Northrop Corp., whose F18 fighter plane is under challenge, has increased the political breadth of its lobbying team in Washington while remaining solidly hooked into the "old boy network" of military officers.

The political spectrum of the aerospace firm's new lobby team now stretches from Joel B. Paris III, Georgia's National Guard director when President Carter was governor, to William E. Timmons, formerly President Nixon's liaison with Congress.

And judging from this year's lobby reports filed with the House of Representatives, Northrop is backing away from its old-style lobbyists, who gained notoriety by taking Washington influentials goose hunting on Maryland's Eastern Shore.

"The ranks of the old-fashioned good old boys, both up here and among the lobbyists, are thinning out," said one long-time congressional observer of defense lobbying. "Today's senator or congressman is more likely to want a position paper than hear a lobbyist tell him the latest dirty joke before saying what he wants."

One of Washington's most celebrated "good old boys" in the military lobbying set is retired Maj. Gen. Winston P. Wilson, former head of the National Guard Bureau at the Pentagon. Northrop paid him a total of $115,000 from 1971 to 1974, according to the Defense Contract Audit Agency.

Of that $115,000, the government allowed Northrop to charge $24,000 to the taxpayers as contract costs.

But Wilson's role with Northrop is fading, if reported earnings are a reliable indicator. Northrop said it paid Wilson $39,000 in 1974. Wilson himself, in his latest lobby report filed with the House, said Northrop paid him $5,800 for the first quarter of 1978.

Wilson's one-time deputy in the National Guard Bureau, retired Maj. Gen. John J. Pesch, formerly director of the Air National Guard, said on his lobby form signed April 25 that Northrop paid him $7,083 for the first three months of 1978.

Northrop's new Georgia connection, Paris, a retired Air Force colonel, was appointed adjutant general, the head of the Georgia National Guard, by then governor Carter in November 1971. He served until January 1975. Paris states in his latest lobby report that Northrop paid him $1,000 in 1977. A Northrop spokesman said Paris is still on the company payroll.

Timmons, who filed in April as a Northrop lobbyist, represents the new breed dominating today's lobbying fraternity - cool, shrewd and well connected. He is not the "good old boy" back slapper of the old days but "almost diffident," said an observer of Timmons' lobbying.

Timmons said on the preliminary lobbying report he signed on April 4 that he could not yet estimate how much Northrop would be paying him.

Northrop has hired additional congressional expertise for its Washington lobbying operation by employing the McLean, Va., consulting firm headed by Jack McDonald, a Michigan Republican who served in the House from 1967 to 1973. McDonald said his firm's Northrop representation is done by James McDonald, no relation, an active Democrat who formerly worked in the U.S. Information Agency's congressional liaison office. The McDonalds said Northrop paid them $6,750 for the first quarter of 1978.

Legal and public relations beyond that provided by the corporation's inhouse employes comes from Washington lawyer Paul Arneson of Williams and Jensen and from Stanley L. Sommer, the latter being the highest paid of the current crop of registered Northrop lobbyists.

Sommer, a Washington newsman and staff member of the Senate Appropriations Committee before going into public relations, made news in 1964 when he disclosed that he had hosted the late Sen. Everett M. Dirksen (R-Ill.) at Bobby Baker's Carousel Motel in Ocean City, Md.

Sommer's public relations firm had received $824,000 from Northrop through 1974, according to the Defense Contract Audit Agency. His most recent lobbying report, signed April 20, states that Northrop paid the firm $15,000 for the first quarter of 1978 - a rate that would be $60,000 for a year.

Northrop signed an agreement with Sommer in 1975 calling for his firm to "represent Northrop Corp. in its relations with the Congress and related units of the federal government. Specifically, by contact with congressional leaders and committee staffs, promote Northrop products and services by providing information on programs and proposals made to the agencies and departments of the United States government. To do this, it will be necessary for you to maintain daily contact with committees having jurisdiction over those departments and agencies with which Northrop does business . . ."

The Defense Audit Contract Agency, in reviewing Northrop's billing of the government for Sommer's services, said the charges were "questionable" because they represented nonreimbursable lobbying activities. However, the government ultimately agreed to let Northrop charge it $535,000 of the $824,000 paid to Sommer's firm through 1974.

Northrop has hooked into the "old boy network" through the scores of military officers it has hired after they leave their services.

According to the Pentagon's latest rundown of retired and former military officers on the payrolls of defense contractors, Northrop, in fiscal 1977, had 61 former military officers in its employ - triple the 20 on the payroll of McDonnell-Douglas, the aerospace contractor that got the most defense contracts that year. (A Northrop spokesman said its subsidiary, Northrop Worldwide Aircraft Services, needs military expertise for the maintenance it performs on military aircraft.)

While McDonnell-Douglas ranked first in dollar awards in fiscal 1977, Northrop ranked 10th with just under $1 billion worth or Pentagon work: $986.2 million. Lockheed, the second biggest defense contractor in fiscal 1977, had 68 fromer military officers on its payroll.

Northrop's prosperity, if not its survival as an airplane builder, depends heavily on selling its fighters over seas. The company's F5 light fighter has been sold to countries all around the world but not to any U.S. military service for combat.

To keep up its overseas sales, Northrop is anxious to sell abroad the F18 fighter it is building with McDonnell-Douglas. Currently, the F18 is slated to be sold in fighter and ground attack versions only to the U.S. Navy and Marine Corps. Iran has expressed an interest in buying a tailor-made F18, but the Pentagon is resisting the idea.

Last week, Sen. Gary Hart (D-Colo.) urged his Senate colleagues to kill the F18 program. He said the plane is running way over its predicted cost and would not be as good as the existing F14 in combating the Soviet cruise missile threatening Navy Ships.

Hart noted that Navy Secretary W. Graham Claytor earlier this year argued for killing the F18 and using the money to buy more F14 fighters and A7 attack planes. The Senate rejected Hart's amendment by 68 to 22. Afterward, Hart told reporters there was temendous contractor lobbying for the F18, including a call to him from a Northrop lawyer he would not identify urging the senator to withdraw his amendment.

The Navy is expected to continue to be short of airplane money, keeping the F18 under heavy challenge in the Pentagon, White House and Congress. One of the plane's big protectors is House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.). The F18's General Electric engines are being built in Lynn, Mass.

The continuing challenge to the F18 helps explain why Northrop is beefing up its Washington lobby operation.

Thomas V. Jones, head of Northrop, has seemingly weathered the scandal of his company making $150,000 in illegal campaign contributions to Nixon, of hiding overseas accounts for paying middlemen involved the selling of Northrop products and on his own felony convictions for the illegal campaign gifts.

Now the big question is whether the F18, with a hoped-for lift from Northrop's lobby team, will climb or be shot down by its critics.