A McLean importer-exporter and a resident of Seoul were indicted here yesterday on charges of trying to smuggle out of this country for sale to Iran 34 sophisticated gyroscopes used in American-made fighter planes and cruise missiles.

The indictment in U.S. District Court charges Sung Bong Kim, 41, of 8303 Berne Forest Ct., McLean, and Jung-Sool Oh, 51, a former colonel in the South Korean army, with conspiring to violate the Arms Export Control Act, which regulates exports of sensitive military equipment.

According to the indictment, Kim and Oh were to receive $80,000 for securing and shipping the gyroscopes to an Iranian in Tokyo named "Mohamed."

The instruments, manufactured by Litton Industries, are used in the navigation systems of F5, F15 and F18 jets and in cruise missiles. At one time, Iran's air force had 50 F5s, which now are more than a decade old.

Since the outbreak of war between Iran and Iraq in September 1980, the State Department has prohibited the export of sensitive military equipment to both countries. In recent years, Iran repeatedly has sought to purchase replacement parts illegally.

Kim, president of S.K. International Inc. at 9001 Braddock Rd., Springfield, was arrested Sept. 18 at National Airport as he was about to fly to Toyko, and is free on $100,000 bond. Oh, president of DAEJOO Trading Co. Ltd. in Seoul, is a resident of South Korea, with which the United States has no extradition treaty.

Thomas Green, Kim's lawyer, declined to comment on the case.

The indictments resulted from an investigation by U.S. Customs agents Donald Bludworth and Robert Fischer, who posed as businessmen able to provide gyroscopes.

According to the indictment, Kim and Bludworth met at the Tysons Corner Holiday Inn on June 11 and discussed ways of circumventing U.S. licensing requirements for the export of military equipment and spare parts.

Negotiations for the sale of gyroscopes continued during the next several weeks in a series of meetings and telephone conversations among Kim, Oh, Bludworth and Fischer, the indictment states.

On Aug. 5, Bludworth supplied Kim with the serial numbers of 14 gyroscopes that were to be sold to Mohamed at a price of $25,000 each, according to court papers.

For each gyroscope, the papers state, Bludworth's company was to be paid $14,520, Kim's company was to receive $1,452 profit, Oh's firm was to receive $726 for repacking in South Korea before transhipping to Japan, and $8,302 was to be a kickback to a representative of the Iranian customer.

Three days later, Kim agreed to buy 20 more gyroscopes, according to court papers.

On Sept. 12, the decision was made that the first two gyroscopes would be hand-delivered to Mohamed in Japan by Kim and Bludworth, and arrangements were made for the two men to fly to Tokyo on Sept. 18, according to court papers.

When Kim arrived at the airport on Sept. 18, one of the gyroscopes, wrapped as a Christmas present, was secreted in his suitcase, and in his briefcase he carried a document falsely describing the instrument as a compass for civilian aircraft, according to the indictment.

He was arrested immediately after he checked his suitcase for the flight.

The maximum penalty for the conspiracy charge is a five-year prison term and a $10,000 fine.