Fairchild Industries Inc. won the unanimous approval of the Federal Communications Commission yesterday to enter a joint venture with Continental Telephone Corp. that should propel the Germantown company into the forefront of the telecommunications industry.

The joint venture with Continental, the nation's third-largest independent telephone company, calls for an initial capital investment of $12 million from each company to form a new entity, American Satellite Co. Under the agreement, announced last summer, Continental would own 50 percent of American Satellite.

The company had been known as American Satellite Corp., a wholly owned Fairchild subsidiary since its formation eight years ago. The company has shown a profit, although American Satellite officials point out that the satellite communications venture has the highest five-year growth rate in the industry and, next to American Telephone & Telegraph Co., has the largest market share -- 28 percent -- of the domestic private-line satellite communications market.

The joint venture with Continental assures "our continuity in space both for the present and next generation of space activities and gives us significant space availability through 1995," Emanuel Fthenakis, president of American Satellite, said in an interview yesterday.

"What we're attempting to do is so advanced that we don't see anyone even contemplating a system like this," Fthenakis said."

Fairchild had 1979 sales of nearly $718 million, and Atlanta-based Continental's revenues last year totaled $1.1 billion. The company serves more than 3 million telephones.

The American Satellite operation, while already having business customers as significant as Shell Oil, Bank of America and General Dynamics and a substantial share of government communications contracts, reported a loss of $4.8 million last year, down from a 1978 loss of $6.5 million. Sales rose to $16.1 million from $10.2 million in 1978.

Nevertheless, the satellite services business has just begun to boom, with industrywide revenues having ballooned from only $5 million in 1976 to $68 million last year. It is expected, however, to become a $100 million business by 1982.

American Satellite offers voice, data, facsimile and business video services to more than 190 private and government users across the Continental United States and in Hawaii and Puerto Rico. The system operates through 40 earth stations, a system that will grow to 50 by the end of the year, and provides links through leased space on three Western Union satellites.

The newly formed company also will own 20 percent of Western Union's Westar satellite system. Continental and Fairchild are acquiring a 50 percent ownership in Western Union Space Communications.

The American Satellite system is the nation's first operational digital communications network, speeding transmissions by converting material to numbered form. Officials say the satellite hookups are designed to serve virtually all of a customer's communications needs and can cut communications bills by up to 20 percent.

The custom-designed systems can link computers or offices, and the company says the accuracy rate in transmitting information is not more than one error for every 10 million bits of data.

American Satellite officials also say they are in a prime position for continued growth in light of the prized locations of their earth stations, their long-term commitments for satellite space and their technological success in developing prototype business telecommunications systems that utilize earth stations directly on a customer's premises.