A predawn raid yesterday by D.C. police, billed as the largest such operation in the city's history and designed to crack an alleged secretive, heavily armed network of Rastafarian drug dealers, proved to be a major disappointment, police officials said.

The raid on 69 spots in Northwest and Northeast Washington, code name "Operation Caribbean Cruise" and involving 530 police officers and backup personnel, was designed to net huge caches of illegal drugs and automatic weapons and to lead to as many as 200 arrests.

But when the dust settled, only 27 persons had been arrested -- four fewer than the number of police officers assigned to process the paper work -- and police had recovered about $20,000 in drugs and 13 weapons, none of which were automatic.

At a news conference six hours after the raid, D.C. police officials said they were extremely disappointed with the results and intended to launch an investigation into possible leaks of confidential information about the raids that may have tipped off the suspects.

However, several persons, including a retired D.C. police lieutenant, complained that the police had mistakenly raided their homes.

"Absolutely, it did not fulfill our expectations," said Assistant Chief Isaac Fulwood Jr., sitting next to a paltry display of evidence confiscated in the raids. "Anytime you have something like this you expect major seizures."

Police officials, who had planned the operation over the last 16 months and prepared a 30-page handbook spelling out the plan, briefed some members of the news media prior to the raid and invited them to accompany police public information officers as they drove by houses after warrants were served. A reporter for The Washington Post obtained a copy of the handbook in advance of the operation.

Officials refused to say how much money was spent to conduct the raid, although many of the police officers who executed the search warrants and arrested, processed and booked the suspects apparently were on overtime.

The dismay of police was evident soon after the raid began at 5 a.m., as officers, some solemn-looking and others laughing at their misfortune, congregated around police vehicles outside the targeted homes and packed away their shotguns, bulletproof vests, sledgehammers and helmets.

Two plainclothes officers looked up in disbelief when photographers enthusiastically descended upon them. Told they had the first arrest to be found, one officer turned to the other and said, "If this is the best you've got, we're all in trouble."

Later, a noticeably chagrined Deputy Chief James P. Shugart, 4th District commander and head of the operation, said it was the most ambitious raid ever staged in the city, with about 12 percent of the entire police department's manpower simultaneously executing the search warrants at precisely 5 a.m.

District police were assisted by the U.S. Park Police, who made eight of the 27 arrests, and by officials of the Bureau of Alcohol, Tobacco and Firearms, the Immigration and Naturalization Service and the Internal Revenue Service, all federal agencies.

According to the operational handbook, the raids were the culmination of a 16-month investigation of an organized group of Jamaicans known as Rastafarians.

"The Rastafarians have been involved in numerous homicides with the use of firearms and have been involved in an ongoing war with other groups over territories and are believed to be responsible for over 18 homicides in the city in connection with this war," the document states.

The Rastafarians "favor the use of automatic and semiautomatic weapons coupled with a willingness to use them under any circumstances," the manual stated, adding that the group is "heavily involved in the distribution of controlled substances throughout the metropolitan area."

However, the extraordinarily detailed planning apparently was compromised, and it became immediately evident to police, when they banged on doors with search warrants in hand, that in many cases their arrival was not unexpected.

According to a detective involved in the operation, officers at one house were greeted by a resident who asked, "Oh, is this the Jamaican raid thing?"

In arresting the 27 suspects, police filed 13 charges for possession of marijuana, six for possession of marijuana with intent to distribute, six for violations of firearms or ammunition laws, and a variety of others, including parole violation and other drug violations.

In addition to the firearms and drugs that were seized, police said, they confiscated about 10 pounds of a white powder that they said they suspect is heroin.

Police said they recovered about $14,000 in cash and documents that they said were "indicative of a narcotics conspiracy." They confiscated a recent-model Mercedes-Benz.

Some persons whose homes were raided were critical of the operation, saying that police had received bogus information and had raided their homes by mistake.

"I was awakened by the doorbell ringing and simultaneously I heard a loud knock on the door, and they kept ramming the door with a sledgehammer," said James Bigelow, 58, a former lieutentant with the D.C. police department's Special Operations Division who retired three years ago.

Bigelow said that by the time he and his wife had run down the stairs of their house in the 4900 block of 12th Street NE, "The plainclothes officers all had their guns out and they told us to sit down and freeze."

Bigelow, the brother of former D.C. deputy police chief Houston Bigelow and the father of a 3rd District police officer, said, "Apparently they got some bad information and they neglected to follow up on it before raiding my house." He said police knocked his front door off its frame and "ransacked" the upstairs before leaving empty-handed.

"It was like the allied troops at Normandy," said another homeowner, Ewan Brown, 45, who said he was "terrified" when police carrying shotguns charged through the front door of his house in the 3400 block of Oakwood Terrace NW.

Brown, a part-time employe for 26 years at The Washington Post, said he was born in Jamaica and is still a citizen of that country. He added that neither he nor the nephew who lives with him is involved with drugs and that he is "prejudiced" against Rastafarians.

Brown said that, after a cursory search of his house, a police officer told the official in charge of the search team that "I think we have the wrong house."

The search was continued for about two hours, during which Brown spoke with the officers and pointed out that his house did not match the one described on the search warrant. He said he pointed out that neither he nor his 22-year-old nephew resembles the picture of a man with dreadlocks that police said had sold drugs from the house.

Brown said police, who made no arrests and found no contraband, apologized before leaving the house, which was in a shambles.

Deputy Chief Shugart said that police had received a number of complaints from people who said that police had mistakenly raided their homes. He said that in those cases, police had gone back to the source of the allegations and confirmed that the information in affidavits filed in support of the search warrants was accurate.

"They [people who protested the police actions] don't control all the people in their homestead," he said, adding, "We will work with them to make repairs" of any unnecessary damage done during the raids.

Shugart, defending the quality of the police investigation, said that "every one of those locations that we hit had [drug] sales . . . at least in 1986," and that illegal drugs were sold out of some of those houses as recently as last week.

Sources said that the massive scope of the operation made it very difficult to keep it secret, and that police informants may have "played both sides of the street" and tipped-off residents of the homes to be raided.

"You cannot do something of this nature and be entirely secretive about what you intend to do," Shugart said. "We felt we could have done a little bit better had we been perhaps a little bit unsuspected in our service of these warrants."