MIAMI (AP) _ Two men conspired with Chilean Embassy officials in Washington to defy a congressional arms embargo and ship military aircraft parts to Chile, according to a federal indictment returned Friday.

The 18-count indictment charges that between 1984 and 1986, Arthur E. Kapel, 60, his son Clifford, 37, and their Miami-based Technical Services International Inc. exported and attempted to export more than $250,000 in American-made F-5 aircraft parts to the Chilean Air Force.

''The indictment culminates a yearlong investigation into the illegal export of munitions to the government of Chile,'' said U.S. Customs Special Agent in Charge Patrick O'Brien.

Those shipments went on despite an embargo on military aid to Chile imposed by Congress in 1976. That embargo is to remain into effect until the government of that South American nation makes significant strides in human rights.

Two officials at the Chilean Air Force Mission in Washington, D.C., Lt. Col. Alfredo Guzman and Lt. Col. Patricio Contreras, were named as unindicted co-conspirators.

The indictment said federal agents seized invoices, orders, and messages recording deals of spare parts between TSI and the Chilean officials.

One overt act listed in the indictment involved a telex from Clifford Kapel to Contreras at the embassy regarding the delivery of F-5 windshields.

He is also accused of meeting with Guzman at the embassy in Washington to discuss the sale of military spare parts.

Guzman and Contreras, whose whereabouts were not known, could not be indicted because they have diplomatic immunity in the United States, federal officials said. A State Department spokesman in Washington told The Associated Press the department had not been informed of the indictment by the U.S. Attorney's office in Miami and had no official comment.

The first secretary at the Chilean Embassy here, Jorge Canelas, said he had no information about the case. According to a secretary at the Chilean Air Force Mission, Guzman was not expected back until Monday and Contreras was out of the country.

The head of the mission, Col. Daniel Moraga, was not available for comment.

Customs agents arrested the Kapels in Miami last July. Clifford Kapel was arrested when he returned from the Chilean Air Force Mission in Washington, where he had just obtained a $200,000 contract for additional sale of plane parts to Chile, O'Brien said.

Although not mentioned in the indictment, a government affidavit last July also suggested that some of TSI arms shipments may have gone to Iran.

The Kapels have been out on $25,000 bond since their arrest and will surrender to the U.S. Magistrate in Miami on Tuesday, O'Brien said. He added that TSI has licenses to operate and is still in business.

''Our position is that the Kapels did nothing wrong because the embargo law is so complicated that even the government doesn't know what a prohibited article is,'' said Ben Kuehne, an attorney for the Kapels. ''They didn't know what they were shipping was illegal.''

O'Brien said that is a common defense, adding the government must prove the Kapels knew what they were doing was wrong.