Ernest A. Dow Sr., 51, executive director and cofounder of the Council on African Affairs here and a former assistant dean of education at the old Federal City College, died of a heart attack Thursday at Howard University Hospital. He has been ill for about a year.

Mr. Dow moved to Washington in 1971 when he joined Federal City College as assistant dean of education. He left in 1975 to work as an education consultant to government and private industry.

In early 1977, Mr. Dow helped found the Council on African Affairs, a private nonprofit organization whose purpose is to provide economic and educational assistant to African countries through private grants.

Mr. Dow, who lived in Washington, was born in British Guinea (now Guyana). He came to this country in 1947 and, in 1951, graduated from Wagner College at Staten Island, N.Y. In 1953 he became a U.S. Citizen and earned a degree from the law school of Brooklyn College of the City University of New York.

After practicing law in Staten Island and serving as clerk of the Staten Island court, he was appointed education director of New York City's Manpower Program in the early 1960s.

Mr. Dow was a member of the Adult Education Association of Greater Washington.

In 1973, he represented the U.S. as an advisor to the UNESCO-spondored conference on worldwide education held in Tokyo, Japan.

Survivors include his wife, the former Dorothe Rohan, and a son, Ernest A. Jr. of Silver Spring, and four other children, Pamela Gibson and Emily Dow, also of Silver Spring, and Doreen and James Dow both of Washington, and his mother, Josephine, of Georgetown, Guyana.