Even in an industry noted for its bravado, Northrop Corp.'s multimillion dollar gamble with its sleek, sparkling red Tigershark F5G fighter ranks as a twin first.

The California-based firm has sunk more than $300 million into the development of a plane for which no firm buyer has yet appeared. And all the funds came from Northrop: the Tigershark is the first modern-day fighter to be developed totally without government support.

"I don't think we've ever seen an aircraft built without a firm order," said C. Robert Gates, the Northrop vice president who heads the Tigershark project. "We did it because we feel the market is there and believe in the validity of progress. There has to be an investment to get there."

Northrop's investment in the plane, which was rolled out of the firm's Production Development Center near here last Sunday amid great pomp, has been substantial. Thomas V. Jones, Northrop's chief executive officer, said $154 million of the $300 million outlay on the F5G so far was spent in 1981. Spending this year is expected to total $250 million.

The company has been writing off expenditures as they occur. Officials deem that approach conservative, proper accounting. But it has created havoc with recent company profit-and-loss statements. Northrop reported a $1.6 million second-quarter loss this year--its second-straight quarterly loss--mainly due to F5G expenditures. That compares with a $5.2 million profit one year earlier. The firm said the deficit would have been wider if the estimate for 1982 income taxes had not been revised. Sales, primarily for various types of Northrop's longer-range F5 fighters and for the new Navy F18A, for which it is the prime subcontractor, rose 21 percent.

If the lack of F5G sales concerns company executives, it was not evident at the lavish Tigershark roll-out last weekend. Exuding confidence, Gates said the company is talking with 42 countries about possible purchases and "the sales program is progressing along." Representatives from several of those nations--Egypt, Turkey and the United Arab Emirates--attended the roll-out ceremony. So did Sen. Ted Stevens (R-Alaska), the Senate majority whip and chairman of the defense appropriations subcommittee.

Stevens noted the aircraft "can be offered to friendly countries without depleting our defense weapons reserve" and said it has "a lower acquisition cost than any of its competitors."

Northrop has priced the intermediate-range plane at $9 million, below that of the competing $13 million General Dynamics F16/79, and of the French Mirage and the British Harrier. Northrop also boasts that its craft uses half the fuel of comparable fighters, requires 52 percent less maintenance manpower and has a 63 percent lower overall operating and maintenance rate.

Company officials estimate it will replace some 2,500 earlier F5 fighters used by 30 nations to counter Soviet-designed MiG21 and MiG23 jets. The Tigershark is to be flight tested in September at Edwards Air Force Base in California.

Although the plane is less sophisticated than fighters like the U.S. Air Force's F16, it still appears to be a large improvement over earlier F5 models. It is a Mach-2 class fighter equipped with an avionics system that allows it to be used around the clock in air-to-air and air-to-ground combat missions. Powered by a General Electric F404 engine, the F5G has 70 percent greater thrust than the current F5E. The company says the Tigershark can be combat-ready and flying at 17,000 feet within three minutes after being ground-launched.

Another innovation is an aircraft computer with a head-up display that coordinates the plane's weapons systems, allowing the pilot to fire weapons without looking down. An improved seat and headset design increases over-the-shoulder visibility.

Military analysts believe the improved efficiency and agility will make the Tigershark a top-class fighter into the 1990s.

In late June, company chairman Jones announced that Northrop would slow the F5G rate of production because of the lack of sales. He blamed the action on "a consequence of delays in government commitments." That, along with other statements by company officials, suggests Northrop is distressed at the Reagan administration's delay in approving F5G sales.

The company proposed a $1 billion sale of 100 Tigersharks to Taiwan last January, but the U.S. government--which must approve all foreign military equipment sales--scuttled the deal after objections were raised by the People's Republic of China. Company officials still are awaiting a clear signal from the White House about which allies will be able to purchase the F5G. Some analysts viewed Jones' production slow-down order as a means of pressuring the administration to speed up its sales review.

Despite the difficulties--and the fact that the innovative methods favored by Jones are on the line as much as the aircraft itself--he and others remain confident that the F5G can find a successful niche in the air forces of developing Third World nations. And Northrop executives believe the firm's private financing mechanism will set a precedent for the industry. "What we are doing together can mark the beginning of a new relationship" between government and the private defense sector, Jones said. "It is the strength of the private sector being brought together with the needs of the public sector."

Despite the slow acceptance of the Tigershark, industry analysts see the company's position as financially secure because of its diversity in the defense field. Contracts for the F18 are increasing. The firm is the prime contractor for the Stealth bomber, which is being designed to evade sophisticated radar and could generate more than $30 billion for Northrop by the end of the decade. Northrop also has garnered a $300 million order to supply avionics for the B1 bomber and a $1.1 billion order for an MX missile guidance system.

Jones' decision to slow production of the F5G--which could postpone deliveries one year until 1985--will reduce annual production costs, which is expected to materially improve Northrop's earnings picture by the end of this year. Jones is philosophical about the difficulties the plane has faced, comparing its development to raising a child.

"You put your best effort into them," he told his audience at the roll-out ceremony. "They take on a character of their own and sometimes succeed beyond your expectations." Graphic: Photo By John Ridgway for The Washington Post An F5G in production: Northrop expects the $9 million plane to replace 2,500 earlier versions of the F5 used by 30 nations. CAPTION: Picture 1, Northrop's F5G during its rollout last Sunday. The company is talking with 42 nations about sales of the plane, which has put Northrop in the red recently, By John Ridgway for the The Washington Post; Picture 2, An F5G in production: Northrop expects the $9 million plane to replace 2,500 earlier versions of the F5 usd by 30 nations, By John Ridgway for the Washington Post