Picture, A-10A Thunderbolt II, By Carol Porter -- The Washington Post; Graphs 1 and 2, Fairchild and VSI profits and sales for five years.

Fairchild Industries Inc. announced plans yesterday to make the largest purchase in its history by buying for $280 million in cash and stock VSI Corp., a California-based worldwide manufacturer of plastics, aircraft parts and a variety of tooling and fastening systems for aircraft.

The purchase -- if approved by the boards and shareholders of the two companies and by federal antitrust officials -- potentially could raise Fairchild's yearly sales figures by close to 50 percent and for the first time put the Germantown aerospace, communications and industrial company over the $1 billion sales mark.

VSI, which is based in Pasadena, will become a separate subsidiary of Fairchild and will maintain its own management team, according to officials of both companies.

Fairchild officials view the purchase as yet another step in the company's efforts to transform a defense and aerospace concern into a diversified firm emphasizing communications services and industrial products. That program recently was given inpetus by the partnership between Fairchild and Continental Telephone Corp. in American Satellite Co., which had been a wholly owned Fairchild ventures.

The Fairchild-VSI merger "coincides with our long-term strategic plan announced in 1972 calling for the development of three complementary lines of business: a broad and balanced military and commerical aerospace activity, communications hardware and service based on satellite technology and industrial/commerical products," said Fairchild Chairman Edward Uhl. "VSI will balance Fairchild's overall business base by contributing one-third of total revenues."

Fairchild is offering $45 a share for the 2.7 million shares of VSI stock, which makes up 42.4 percent of the company's outstanding shares. The remaining 3.6 million VSI shares would be swapped for a new Fairchild preferred stock set up to produce a value of $45 a share. VSI closed Monday on the New York Stock Exchange at 39 3/4.

VSI has shown a steady, recent growth pattern, as the company's sales have grown from $211 million just two years ago to $391.8 million for the 1980 fiscal year ended on June 30. Among other things, the company is one of the world's largest manufacturers of aerospace fastening systems and has more than 70 percent of the domestic plastics tooling industry.

The VSI deal, according to a Fairchild spokesman, has no effect on the company's continuing interest in merging with Bunker Ramo Corp., the sururban Chicago company that has resisted the takeover offers. "When in doubt, you use your money while you've got it," one Wall Street analyst said of the VSI purchase. This analyst also said VSI's fastener business, a significant chunk of its sales, would not be quite as strong in the middle of the 1980s as the aerospace industry continues to feel the effects of changes in transportation industries. "But now VSI might be able to grow a bit faster using Fairchild's resources."

Nevertheless, a VSI spokesman would not say what made the Fairchild offer any more appealing then a $40-a-share cash offer from Emhart Corp. for VSI last year. Both sides of that transaction terminated the deal on Dec. 22.