Earl Charles Bowersox Jr., 53, a retired Navy captain and a vice president of Calspan Field Services Inc., was found dead Tuesday at a hotel where he was staying in Buffalo, N.Y. The Erie County (N.Y.) Medical Examiner's Office said the cause of death was a heart attack.

Capt. Bowersox, who had lived in Great Falls since retiring from the Navy in 1975, was in Buffalo on business.

Capt. Bowersox, who was born in Baltimore, graduated from California Maritime Academy in 1948 and then was commissioned in the Navy. He later graduated from the Armed Forces Staff College and the Defense Language Institute.

Most of his career was in intelligence. His assignments included tours as special assistant to the director of the Defense Intelligence Agency, chief of the Intelligence Support and Indications Center of the U.S. Atlantic Command and as an assistant in the office of the Chief of Naval Operations.

He also was a naval attache for air at the U.S. embassy in Tokyo. He later planned and became the first commanding officer of the Intelligence Center Pacific, a joint service command in Hawaii. He held that post when he retired.

From 1976 to 1978, Capt. Bowersox worked for the House Appropriations Committee. He then was a private consultant. He joined Calspan Field Services as vice president for command support systems early in 1980.

His military decorations included two Legions of Merit, two Meritorious Service Medals and the Navy Commendation Medal.

Capt. Bowersox was a member of the American Society of Naval Engineers, the Armed Forces Communications and Electronics Association, the Astronomical Society of the Pacific, the Association of Old Crows, the Polynesian Voyaging Society and the Fairfax Rod and Gun Club in Manassas.

Survivors include his wife, Glennis E., of Great Falls; four sons, Dr. Jon C. of Pasadena, Calif., Matthew P. and Patrick E., both of Wahiawa, Hawaii, and Timothy J. of Great Falls; one daughter, Kathleen K., also of Great Falls; his mother and father, Marjorie M. Cobb of Towson, Md., and Earl C. Bowersox Sr. of Upper Marlboro; one half-sister, Agnes Bowersox of Kensington, and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to the Washington Cathedral.