A Frostburg, Md., man received a suspended sentence of 12 months in jail and a $1,000 fine in Arlington County Circuit Court yesterday for his role in the beating death of a Washington campaign worker near the Iwo Jima Memorial in the fall of 1976.

Alan J. Arnone, 24, had been convicted April 26 of involuntary manslaughter for his part in the death of Ronald J. Pettine, a worker in the 1976 presidential campaign of Rep. Morris K. Udall (D.-Ariz.).

Judge William L. Winston followed the recommendation of the trial jury by suspending both the jail term and the fine. Involuntary manslaughter carries a maximum penalty of five years in prison under Virginia law.

Arnone, who is 4 feet 9 inches tall and suffers from several birth defects, was placed on three yearsh probation. Under the sentence he is to spend one year living in a Baltimore health clinic where he will receive psychiatric care.

Arlington prosecutor Kenneth Melson said he had no quarrel with the sentence. "This is a case where the jury knew, everything that we knew. There is no reason not to abide by the jury's [recommendation in sentencing]," he said.

During the trial, Arnone testified that he kicked Pettine as he was being beaten by two other men in the woods near the memorial on the night of Oct. 2, 1976. Arnone's lawyer, William D. Dolan, portrayed his client as a "follower, a tag-along . . . a mascot . . ." of the other men, Michael G. Simoneau, 18, of Falls Church and Charles A. Bamman, 22, of Arlington. Both men are now serving lengthy prison sentences for first-degree murder in Pettine's death.

Arnone told the jury that he had been sexually abused by Simoneau and Bamman several days before the slaying. "I was afraid of what Chuckie (Bamman) might do to me. He said, "If you don't kick him, I'll kill you.'" Arnone said.

Arnone testified that he kicked Pettine because he was afraid that treat would be carried out.

In previous testimony, simoneau had said the three men went that night to the memorial, known as a rendezvous for homosexuals, "to smack around a few queers."

Pettine, who was married and the father of two, was described during the trial as a homosexual.