When the missiles start flying in the Gulf of Sidra, the phone starts ringing in the K Street office of G. Henry M. Schuler.

The "expert."

Schuler, who holds the Dewey F. Bartlett chair in energy resources and security studies at Georgetown University's Center for Strategic and International Studies, is one of a handful of Libyan experts sometimes consulted by Congress, the administration and the press.

His position is a nonteaching "research appointment" -- in a world of studying oil and foreign policy reports, testifying before Congress, working the telephones, writing op-ed pieces and power lunching.

Schuler says CSIS is located in a downtown office building instead of the Georgetown campus for good reasons: "We're closer to the Hill and . . . National Security Council, where we like to have some impact," he says.

Schuler says he doesn't know the president's new national security adviser, John M. Poindexter. But on April 1, his friend Robert McFarlane, the president's former national security adviser, will move down the hall -- joining CSIS as a "counselor" to work on international security and arms control.

Although Schuler's expertise is in oil, he calls Libya his "avocation." His views may not be shared by other experts, but he lived in Libya first as a foreign service officer and then as a big oil company representative, and he has met Muammar Qaddafi, if only briefly.

He is asked if Qaddafi is nuts. (Everybody asks this, he says.)

The answer:

"No, and I was asked this by a very senior administration official the last time around in 1982. Qaddafi is a zealot and a revolutionary, and Lenin said a revolutionary probes with a sword until he encounters steel. Qaddafi has been probing now for 17 years and has never encountered steel . . . "

Now, of course, he has.

Yes, Schuler concedes, U.S. carrier groups and jet warplanes are "steel"; nevertheless, he thinks a military confrontation is unnecessary and dangerous.

"I have been a longtime advocate of getting tough with Qaddafi," he explains, "but my preferred vehicle for that was economic sanctions, tough sanctions to isolate him politically and economically, because without the oil exports and the revenues he can't stir up terrorism around the world or suppress the domestic discontent . . ."

Unfortunately, he says, it's "easier" to mobilize the U.S. Sixth Fleet than to make economic sanctions stick. For one thing, the oil companies -- Schuler was director of W.R. Grace's oil subsidiary in Tripoli from 1966 to 1969 and then Nelson Bunker Hunt's oil man there until 1974 -- fought against President Reagan's January economic sanctions with a good measure of success.

Now, says Schuler, "The president gives the orders and Cap Weinberger says, 'Aye, aye sir!' and off they go. With sanctions you've got to get all those bureaucrats in the State Department . . . and all the vested commercial interests to work together, so it's just easier to use the military . . . and I think that's a damn shame!"

One concern, he says, is that when Qaddafi finds he can't knock U.S. warplanes out of the sky, "he'll resort to terrorism. I would expect to see incidents, not in the next day or so, but in the coming weeks and months and years directed against U.S. installations and citizens here and abroad."

The polished and plush fourth floor CSIS suite looks like a law office.

A "CSIS People" flyer on the coffee table says, "CSIS President Amos A. Jordan discussed the significance of Chinese President Li Xiannian's recent U.S. visit on USIA's 'America Today' program . . . G. Henry M. Schuler testified on the role of synthetic fuels in military preparedness before the House Armed Services Committee's subcommittee . . . "

Schuler's office is small, filled mainly with bookcases lined with copies of Foreign Affairs and various academic journals. Schuler himself is a tall man with glasses and a firm handshake.

He is wearing a blue blazer and has a tight-lipped smile. As he talks, he sits upright at his desk with hands folded before him, as if testifying before a committee.

Libya, with only 3.6 million people and 2 percent of its land arable, calls itself the "Socialist People's Libyan Arab Jamahiriya," according to the World Almanac and Book of Facts for 1986. What is "Jamahiriya"?

It can't be translated, says Schuler. It means that the government is "totally unstructured" and that Qaddafi runs the show.

Qaddafi in person, he says, was "not impressive . . . His physical stature was not commanding."

Of course, that was 1969; they met briefly in a group of others after Qaddafi took power in a bloodless coup. In 1952, Libya became an independent constitutional monarchy; over the centuries, it had been ruled by Carthage, Rome, the Vandals, the Ottomans, Italy, Britain and France.

In the early 1960s, when Schuler was a U.S. foreign service officer in Libya, he met his wife, also in the foreign service there. The first two of their four children were born in Libya.

Before Qaddafi, he says, it was "fun . . . I'm crazy about Libya. I would love to go back there with my family" if it were possible. Schuler says he likes the Libyans: "I don't accept the stereotype that they are a shiftless, lethargic people."

After Qaddafi took over, "Life got very dreary . . . The contrast was great. Increasingly as you went around, you'd find yourself, as you were walking down the street at night from the hotel, people would be following you in a Volkswagen."

Schuler moved his family to London in 1970 and felt more comfortable after that. He made frequent trips to Libya to keep up with his work.

Eventually, he says, he got out of oil and into academia, which pays a lot less, "because I'm concerned about my draft-age sons. I started worrying about it in 1971, when they were 7 and 5."

He still worries about failures of U.S. Middle East policy that could affect his sons.

"If the call came I expected them to answer it," says Schuler, "but I wanted to be able to look at myself in the mirror, too."