LOS ANGELES, Mar. 12 – Three persons were arraigned Monday in Los Angeles federal court on charges they plotted to free a convicted airline hijacker and another man from Los Angeles County Jail by kidnapping a consul general.

A U.S. attorney said that had the kidnapping been carried off, “It would have brought this country to its knees.”

Karen Marie Forbes, 22, also known as Maria Theresa Alonzo, a former follower of Charles Manson; Garrett Brock Trapnell, 36, who hijacked a Boeing 707 in 1972 to bargain for the release of a man who helped him rob the Princess Louise Restaurant of $10,000, and Robert Bernard Hedberg, 37, were named in the conspiracy.

Federal Magistrate Vanetta Tassopolus set preliminary hearing for March 21 and remanded Miss Forbes to sheriff’s custody in lieu of $350,000 bail.

FBI agents said the three planned to kidnap an unnamed consul general from one of eight foreign nations to bargain for the release of Trapnell and Hedberg.

The plot was broken up Saturday when Miss Forbes was arrested in her Hollywood apartment, Agents said, adding that a person she asked to participate told agents of the conspiracy.

During Monday’s arraignment, Assistant U.S. Atty. Robert Perry said Miss Forbes “came perilously close to commission … of the kidnaping.

“It would have involved this country and another and … brought this country to its knees,” Perry said.

Sheriff’s deputies who aided in the arrest Saturday said Miss Forbes’ forehead bore an “X,” the symbol used by followers of Manson who stood vigil outside the Los Angeles courthouse during his trial.

Manson and three young women were convicted in the slaying of actress Sharon Tate and six other persons.

An FBI spokesman said the intended kidnap victim was to have been a consul general from either Estonia, Paraguay, Uruguay, Canada, France, Germany. Switzerland or Haiti.

Although Trapnell is serving a life sentence in New York for the abortive hijacking of a Los Angeles-to-New York commercial jet, he was returned to California in January to await sentencing Thursday in Long Beach Superior Court for participating in the daring 1971 $10,000 robbery of the Princess Louise.

Hedberg, 36, who has a 20-year record of heroin-related arrests, was ordered Feb. 26 by Judge Max Wisot to undergo a 90-day psychiatric test at the California Institute for Men, Chino, following a parole violation hearing. Wisot ordered Hedberg to appear for sentencing May 29.

During the seven-hour skyjack, while Trapnell held the flight crew and 93 passengers at his mercy with a .45-caliber pistol, he demanded the release from Dallas County Jail of a man who three months earlier also participated in the Princess Louise holdup.

At the time, Federal Aviation Administration officials and Texas police said they knew of no connection between Trapnell and the second man, Jorge Antonio Padilla.

Thirteen months later, on Nov. 5, 1972, Padilla pleaded guilty in San Pedro Municipal Court to participating in the Princess Louise robbery. Judge Walter Binns sentenced the defendant Nov. 29 to serve from five years to life. Padilla has since been returned to Texas to continue serving sentences for other robbery convictions.

Trapnell pleaded guilty Feb. 21, in Long Beach Superior Court to one count of armed robbery for his participation in the Princess Louise case. He will appear Thursday before Judge Elsworth Beam for sentencing.

Deputy Dist. Atty. Robert Berger Monday said he will recommend the maximum sentence for Trapnell — five years to life.

During pretrial proceedings last December in New York in connection with the skyjacking, Trapnell pleaded not guilty by reason of insanity. If he is indeed insane, his background provides a few explanations.

Trapnell’s father was an Annapolis graduate who rose to the rank of commander but married five times. Trapnell’s father and mother divorced when he was four and he moved from home to home, including a stay in Panama.

It was in the Canal Zone that Trapnell’s criminal record began — an arrest at the age of 15 for petty larceny. Five years later, Trapnell was given an undesirable discharge from the Army.

Six weeks later, following a reported stint as a gunrunner to Fidel Castro, Trapnell was returned to the United States following an arrest by Cuban Army Military Intelligence for “investigation.”

Since then, Trapnell has been arrested in 11 states and Canada for armed robbery, auto theft, forgery, check fraud, kidnaping, smuggling and, finally, the 1972 skyjack of a Trans World Airlines Boeing 707. In addition to the release of Padilla, Trapnell also demanded $306,800 — money he said the government owed him for seizing a boat the year before — an interview with President Nixon and freedom for black activist Angela Davis.

Trapnel was shot in the left shoulder and hand by an FBI agent posing as a crewman after the plane landed at Kennedy International Airport.

In March of 1970, Trapnell was accused of stealing a plane from Orange County Airport in Santa Ana, flying to West Palm Beach, Fla., then on to Freeport in the Bahamas. He allegedly held up the Emeralds of Colombia, Ltd., taking $100,000 in gems and then flew back to Florida.

Indicted by a federal grand jury in Miami on the jewel and plane theft charges, Trapnell next turned up in January, 1971, in Syracuse, N.Y., where he was captured in a bus station after breaking out of a mental institution in Montreal.

“He told me he used to stick up banks in Canada all the time,” Sgt. Robert Kinsey, a senior Harbor Division robbery detective said Monday. Kinsey was one of two detectives who returned Trapnell from New York in January to face the Princess Louise robbery charges.

“Trapnell claimed to have gotten away with robbing Canadian banks seven or eight times,” the investigator said. “Said he used to just grab a plane for the weekend and hold up a bank.

“Don’t be fooled, though,” Kinsey said “Trapnell is very intelligent. Unlike other robbers who stick with one sort of job — liquor stores, cabs, jewelry — Trapnell keeps doing different things just for the challenge, to see if he can do it.

“He stuck up Coberly Ford once for $5,000, but instead of just whipping out a gun, went through this elaborate sham for more than an hour of wanting to buy a fleet of cars. We figure that it wasn’t until he felt he’d convinced the salesmen that he really knew about cars that he demanded the money.”

Kinsey said an even bigger charade surrounded the Princess Louise robbery.

For three days, three men later identified as Trapnell, Padilla and George Peterson, who is still at large, masqueraded as magazine writers and photographers, convincing owner Jerry Sutton and manager Mike Morrell that they were doing background pieces on Princess Louise II, later constructed in Redondo Beach.

With Morrell as hostage, Sutton was forced to withdraw $10,000 from the Farmers and Merchants Bank at Pine Avenue and Third Street. Sutton and Morrell were later released unharmed.

Hedberg’s criminal record also began at 15 when he was declared incorrigible because of a history as a runaway. His record shows more than 20 arrests, some for assault with a deadly weapon and burglary, but most for heroin possession. He has suffered overdose reactions several times in county jail, records show. He was arrested in the Long Beach area Jan. 29. for suspicion of driving under the influence of a drug.

Although the district attorney’s office declined to prosecute on that charge, Hedberg was continued in custody because of several outstanding warrants filed against him, including unlawful flight to avoid prosecution in connection with a charge of assaulting a police officer with a deadly weapon.

By JOHN SHEEHAN