The pilot of an American Airlines 727 with 85 passengers aboard threatened to set his plane down on a South Dakota Indian reservation recently because he believed a D.C. homicide investigator and another area detective had obtained liquor aboard the plane in violation of federal regulations that prohibit armed passengers from doing so.

The pilot, Donald Heins, said in an interview that he ordered a flight attendant to confiscate whatever liquor the officers had and to warn them that if there were any further such incidents he would "put the aircraft on the ground immediately" and leave them "in the custody of local authorities . . . ."

"They very closely found themselves sitting in the middle of the Cheyenne River Indian Reservation with no way to get home," Heins said. He said he had landed on the airstrip there once "some time ago" and knew that it could accommodate the jetliner.

Heins said he radioed the plane's West-Coast destination to inform airport police of the situation, but police officials there said they found no evidence that the two officers--or an armed female D.C. homicide detective also alleged to have been involved in the incident--had been drinking.

Airport police said that in response to a request from D.C. police officials both District detectives--Sgt. MacArthur James and Detective Anne Fisher--were asked immediately after the July 13 flight if they wished to take breathalyzer tests, but that both declined.

In an interview shortly after the incident, D.C. police chief Maurice T. Turner said James and Fisher "never ordered alcoholic drinks" and "did not partake" of any liquor on the trip. Turner also contended in a prepared statement that the incident was "motivated and perpetuated as a result of a racial issue. The male detective is black and the female detective is white."

Turner said in a separate interview that he was told by Capt. Jimmy L. Wilson, head of the homicide branch, that his "officers' assessment of the situation" was that the issue was exacerbated by racial bias of the flight crew.

"Some people have racial prejudice," Turner added. "I mean they get clearly upset when they see a black man with a white woman," especially a "big black officer with a little white female."

In response to Turner's allegation, Lowell Duncan, American's vice president for corporate communications, said, "It's hard to understand and believe . . . .

"We totally deny that there's any racial bias involved whatsoever," Duncan said. "It's strictly a matter of FAA rules and regulations and American Airlines' rules and regulations."

D.C. police and airline officials said they were aware of no complaints filed by anyone involved. Federal Aviation Administration officials said they are investigating the incident.

Wilson confirmed that James and Fisher were involved in an incident aboard the flight. He said they were on a "successful" and sensitive evidence-gathering mission along with a sheriff's department detective and deputy state's attorney from St. Mary's County, Md., but he asked that their destination and other particulars of the investigation not be revealed.

James and Fisher did not return a reporter's calls concerning the incident. The St. Mary's detective, Cpl. Ernest Carter, declined to comment.

American spokesman Duncan, who said he had not previously heard of a "case like this," said a "very elaborate procedure" exists for allowing passengers--usually law enforcement or military personnel--to board an airplane while armed.

Before boarding, he said, such passengers must present credentials including their picture, signature and authorization from superiors and sign a form agreeing to abide by all FAA rules. One such rule bars armed passengers from buying or consuming alcoholic beverages aboard commercial airplanes.

The three detectives and the prosecutor boarded the plane at Washington National Airport. During the first leg of the flight, Duncan said, one of the male detectives--who were seated together--asked to buy drinks and was refused. The same officer then asked a different flight attendant for a drink and was again refused, Duncan said.

After a brief stop in Chicago, where six of the eight crew members were replaced and Heins became the pilot, flight attendants "saw small miniature drinks being passed" by Fisher toward James and Carter, and they informed Heins, Duncan said. Duncan said the drinks appeared to be Scotch and vodka.

At this point, apparently because the flight crew had not been made aware of Fisher's identity, the attendants thought she was an ordinary passenger, not an armed police officer, Heins said.

When the flight attendant warned James and Carter that the pilot would make an unscheduled landing if there were further attempts to obtain liquor, she also told Fisher to stop passing drinks, Heins said.

Heins said he learned only after the flight that Fisher also was a police officer, and that a flight attendant told him then that Fisher had been drinking liquor on the plane and had purchased miniature bottles of liquor throughout the flight.

"If they're packing hardware, they don't touch a drop . . . ," Heins said. "At that altitude, one ounce of alcohol in the normal human physiology is equivalent to three," and the effect of liquor "will come on them three times faster than they're used to.

"This is the way the rule is written and why the rules are written," said Heins, a former military pilot who joined American in 1965.

Wilson denied that his officers consumed or passed drinks, but said he was told by them that Carter, the St. Mary's County detective, had ordered a drink and was turned down by a flight attendant. Carter refused to discuss the incident, but a county sheriff's department official told a reporter that "If Carter was drinking, it would be a rare damn occasion . . . . It would surprise the hell out of me.

"He doesn't even like to be around drinking . . . ," the official said.

Wilson said District police also were notified of the incident while the flight was still in progress. He said the department asked that airport police meet the plane upon its landing to ascertain the "mental state" of his officers and "to find out if there was a problem" on the aircraft. Turner said police were asked to "see if the officers were intoxicated."

Wilson said he questioned his officers and spoke with airport police and concluded that Fisher and James hadn't "done anything wrong." He said no disciplinary action would be taken.

"I spoke to the airport police deputy chief, who indicated that . . . it appeared to be a racial incident," Wilson said.

The deputy chief told a reporter that he had heard "third-hand" and in "a roundabout way" from an airport policeman that a female member of the crew had allegedly remarked that she did not want "the black officer" to know her address in the D.C. area. Both James and Carter are black.

The deputy chief said he has issued a request for any of his officers who might have heard such a remark to come forward, but that no one has. The unsubstantiated statement was never made a part of any official reports, the deputy chief said, but he said he passed the observation on to Wilson.

Heins said a number of flight attendants had told him that they did not want their "names and domiciles" to be released to any officer because they feared reprisals.