Mayor Marion Barry, wearing a tan safari suit and admittedly excited about his first trip abroad as mayor of the nation's capital, left for a five-nation, 18-day visit to Africa yesterday, a trip he termed an experiment in municipal foreign relations.

The mayor, his wife Effi and mayoral aide Courtland V. Cox, who also wore a tropical-style shirt jacket like those often wore in Africa, left the District Building about 3 p.m. as about three dozen aides waved bon voyage.

The party, which also includes lawyer and D.C. Democratic leader Robert B. Washington Jr. and Carter H. Dove, Riggs National Bank's vice president for Middle East and African affairs, left Dulles Airport yesterday evening. They were to arrive in Dakar, Senegal, this morning.

Later, the group will fly to Monrova, Liberia, where Barry will be among several black American guests invited to observe parts of the 16th annual summit meeting of the Organization of African Unity.

Other stops on the tour include Nairobi, the capital of Kenya, and, following a layover in Lusaka, Zambia, a visit to Dar es Salaam, the capital of Tanzania. The party is to return July 30.

"I've decided," Barry explained "that it's important for the District of Columbia to have relations with a number of foreign governments in terms of economic development and cultural ties as well as personal relationships."

The mayor said he hoped he could find markets in Africa for Washington-based consultant firms and businesses and also develop cooperative relationships that might lead to an exchange of technical advisers between the African states and the District government. Barry is considering one proposal that would make Dakar, the Senegalese capital, a "sister city" of the District.

Barry also said he thought it was important for him to make the visit, which is being paid for by the U.S. International Communication Agency, because it would improve relations between black Americans and their African homeland.

"From a black perspective, it's important that black leadership understand, be a part of and identify with what's happening in Africa," Barry said. When asked what tangible results city residents would see come out of the trip, he answered candidly, "They might not see much. I don't promise that."

The only controversy about the trip has involved South Africa. Barry turned down an invitation to visit that troubled country, saying he did not want to become a vehicle for propaganda of the white minority government.

Self-styled pro-African groups have protested Barry's decision to allow Dove to accompany him on grounds that Riggs Bank helps "prop up" the South African economy by making loans in that country. Dove has refused to discuss the allegations.

Barry has said that he invited Dove because he believes it will be easier to discuss economic development with African leaders if he is accompanied by an international banker.

Yesterday, a New York-based group protesting the alleged role in South Africa of Riggs and other banks announced that it has asked the OAU to bar Barry from the organization's meetings if he insists that Dove accompany him to the sessions.

While Barry is out of town, City Administrator Elijah B. Rogers will act as mayor. CAPTION: Picture, Mayor Barry enters car for trip to airport to begin tour of africa. By Linda Wheeler - The Washington Post