Robert W. Eaves, 75, retired executive secretary of the department of elementary school principals of the National Education Association, died Tuesday at Arlington Hospital. He suffered from a heart ailment.

A leading exponent of the professional role of the principal, Dr. Eaves saw the department's membership increase from 10,000 to 25,000 during his tenure, which spanned 1950 to 1969. The department now is the National Association of Elementary School Principals and operates separately from the NEA.

Dr. Eaves, who was born in Rutherford County, N.C., began his career as a teaching principal in North Carolina after graduating from Weaver Junior College there. He later earned degrees from the University of North Carolina and George Washington University, where he received a doctorate in 1940.

He came here in 1930 as a junior high school teacher in Catonsville, Md., and a year later became principal of Jefferson Elementary and Junior High School in Alexandria.

From there he moved to the D.C. public school system as administrative principal of Thompson Elementary School, a position he held until 1944, when he became secretary of the NEA's national committee on safety education.

Dr. Eaves also served on the faculties of numerous colleges and universities at regular and summer sessions.

He served as a specialist on the extended school service program of the U.S. Office of Education, was a member of the 1946 President's Conference on Highway Safety, the 1957-59 President's Citizens Advisory Committee on the Fitness of American Youth, and the 1967 President's Committee on the Education of the Handicapped.

Dr. Eaves was a prolific author of articles on education. After he retired in 1969, he taught education courses at George Mason University in Fairfax until 1976.

He is survived by his wife, Ruth, of the home in Arlington; a son, Robert W. Jr., of Atlanta; three sisters, Willard Carroll, of Rutherford, N.C., Lola Henderson, of Charlotte, N.C., and Rose Smith, of Forest City, N.C.; three brothers, Marvin N., of Charlotte, George B., of Forest City, and James B., of Macon, Ga., and two grandchildren.