Thomas H. Magness Jr., 75, a retired Army colonel who worked as a consulting engineer in Northern Virginia, died at his home in Arlington Monday after a heart attack.

Col. Magness, who was born in Baltimore, was commissioned in the Army Corps of Engineers following his graduation in 1927 from Johns Hopkins University. During World War II, he was a chemical officer assigned to allied headquarters in England.

After the war, he was a student and then an instructor at the Command and General Staff College at Fort Leavenworth, Kan. During the Korean conflict, he was assistant chief of staff of an Army corps in Korea.

In 1952, Col. Magness was appointed chief of logistics at NATO headquarters in Izmir, Turkey.

From 1955 until his retirement from the Army in 1961, Col. Magness was stationed in the Military District of Washington. He was a chemical officer and also helped develop the Radiological Center of Operations here.

His military decorations included two awards of the Legion of Merit and the Bronze Star.

After leaving the service, Col. Magness was a consulting engineer for the Northern Virginia segment of a national survey of fallout shelters.

Col. Magness was a member of St. Ann's Catholic Church in Arlington.

Survivors include his wife, the former Alice Severs, of Arlington; three sons, Thomas H. III, an Army lieutenant colonel who is stationed in Heidelberg, Germany, and Charles F., a retired Army lieutenant colonel, and David M., both of Falls Church; a sister, Helen Wagoner of Santa Ana, Calif., and eight grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Catholic Charities of the Diocese of Arlington.