Just before he fled Washington earlier this month -- apparently to avoid trial on charges of illegally selling 10,000 machine guns and running a terrorist school in Libya -- McLean arms merchant and mystery man Frank Terpil tried to fashion a bizarre deal that called for deposed Uganda dictator Idi Amin to free the U.S. hostages in Iran.

Amin told Terpil during several phone conversations in late August that he would try to convince Ayatollah Khomeini to free the hostages. Amin also mentioned that he'd like Terpil to help a couple of dozen of his children find a nice parochial school in the United States.

Terpil was arrested last December in New York and charged with trying to sell machine guns to police undercover agents. His trial was scheculed to begin just after Labor Day. Following that trail, Terpil was to face charges of conspiracy in Washington in connection with the operation of a secret training school for terrorists in Libya. Terpil denied all the charges. But on Sept. 4, when he failed to appear in New York for his first trial, a federal judge issued a fugitive warrant for the arrest of Terpil, who had posted a toatl of $125,000 bond in cash, property and other collateral in the two cases.

Three days earlier, on Labor Day, a relaxed and bemused Terpil posed for photographs in front of his Japanese-style mansion just down the lane from Ethel Kennedy's estate in McLean. The house boasts, among other accouterments, a sunken tub, a central courtyard that is a garden, a basement firing range and a bookcase that swings from the wall to reveal a network of tunnels through the house.

Terpil showed a visitor a letter from the IRS demanding nearly $3 million in taxes, interest and penalties for allegedly failing to pay adequate income tax three years ago.

"Isn't that a laugh?" he asked twice.

Along with the criminal charges and the IRS letter, Terpil's name had surfaced in connection with Billy Carter and Libya. Published reports claim Terpil met with Carter to discuss a machine gun sale to Libya. Ridiculous, snorted Terpil, who said he's never met Carter even though they both attended the celebration of the Libyan Revolution in 1979.

But even in the fast, rich and shadowy world of international arms merchants, Terpil's bid to enlist Idi Amin to free the hostages in Iran must rank as a move of extraordinary chutzpah. good will toward himself before he went on trail, Terpil phoned Amin in the fomer dictator's suite at the Intercontinental Hotel in Jidda, Saudi Arabia. Terpil once sold millions of dollars worth of surveillance equipment and explosives to Amin when the former Army sergant ran Uganda with an iron fist. Amin seemed delighted to hear from Terpil and said he'd like to help the hostages.

Terpil says ever since someone showed Amin a T-shirt with his pudgy face and the inscription "Idi Amin -- Emperor of Africa" around it, Amin has thought Americans loved him. In late August Terpil shared a Washington lawyer, Kennety Michael Robinson, with an Abscam defendant, Rep. John Jenrette (D-S.C.). Jenrette and Terpil both tried to convince Amin, who is Moslem, to plead the case of the hostages with Iran.

Amin said he'd be delighted to lend a hand. And he asked if it would be possible to send 24 of his children to the United States to a parochinal school similar to one they attended in Kampala. Terpil, ever the gentleman, said he'd be happy to explore the possibility.

But before that happened, IRS and trial deadlines closed in on Terpil and he fled his home, cutting short one of history's more unusual efforts at international diplomacy. CAPTION:

Picture, no caption, By Rudy Maxa