Two Virginians, weakened by months in a Haitian prison, were acquitted yesterday in Port-au-Prince of charges that they were carrying nearly a ton of marijuana in a light plane when it was forced down by engine trouble last October.

Judge Theophile Jean-Francois announced the verdict as Henry Tiffany, 43, and Jack Melcher, both of Waynesboro, Va., stood before him in the courtroom crowded with onlookers.

"I just jumped up and down," said Patricia Tiffany, the defendant's wife, in a telephone interview from a Haitian hotel room. "I'm so very, very happy." The two men faced possible sentences of 15 years in prison and $25,000 fines.

Jean-Francois, who heard the smuggling charges without a jury, freed the men after deciding that the plane, a twin-engine Beechcraft, was incapable of carrying that much contraband cargo, according to the judge's decree

Tiffany, a lawyer and real estate broker, and Melcher both showed the ill effects of their imprisonment. "He looked kind of pale, sick and skinny," said Patricia Tiffany of her husband.

Tiffany, the father of three, lost an estimated 35 pounds while in the Haitian national prison, and was treated for a rigworm-like condition on his chest, a staph infection, and respiratory and ear infections, according to Washington lawyer Frank Mika, a friend of Tiffany's.

Melcher lost about 4/ pounds and walked with a cane, still favoring a leg injury suffered during the plane's forced landing Oct. 22 on a remote landing strip. Melcher spent the first two weeks in Haiti in the prison hospital.

According to Mika, the pair left Virginia about 2 a.m. on Oct. 22, and encountered engine trouble about 9 a.m. over Haiti. They put down on an abandoned landing strip at the base of a mountain near the village of Aquin.

Mika said yesterday he believed Tiffany and Meicher were on their way to the island of Curacao, "looking at some land or something. I'm not sure exactly what he was going to do."

A cache of marijuana was discovered near the plane the next day and the two, who had been treated as "guests of honour," in Aquin, according to Mika, were taken off to prison in Port-au-Prince.

The men were quartered with two Americans from South Carolina who had recently been convicted of drug smuggling after their marijuana loaded plane crashed on Haiti-the same offense of which Melcher and Tiffany stood accused.

Their prison diet was rice and beans and an occasional dish of goat's meat.Mika said. Toilet facilities were primitive-an open ditch flushed once a day into the street.

The trial was broadcast live on national television, but "the sound was mysteriously cut" when government witnesses gave conflicting testimony, according to Mika, who helped defend Trifany.

Although proseciution witnesses said they had found a trail of marijuana leading from the plane to the larger cache, and even a small amount of marijuana on board the plane, they could not describe the interior of the plane in court nor did they produce any marijuana as evidence, Mika said.

During the trial, the 350-seat courtroom was jammed with 700 people, all of whom periodically "cheered and applauded," Mike said. "The whole thing there was such a farce."

Haiti is one of several countries that deal sternly with foreigners who run afoul of police on drug-relatex matters, according to State Department officials.

The Tiffanys spent yesterday at the Royal Haitian Hotel in Port-au-Prince, "celecbrating very quietly with a group of Haitian friends," according to Patricia Tiffany. She said she and her husband planned to return to the United States tomorrow and that their first priority would be "relaxation."