Retired Navy Capt. Peter F. H. Hughes, 51, an engineering consultant for Northup Services, a research and development firm doing work for the government, died of cancer Friday at Fairfax Hospital.

Capt. Hughes, a native of Chicago, was a 1951 graduate of the Naval Academy at Annapolis. He joined the submarine service and his assignments included command of the USS Trigger and various staff positions in the Atlantic and the Pacific.

He taught naval science at the University of Nebraska and was a graduate of the Armed Forces Staff College. In 1974, he was assigned to the Navy Department as executive director of the Naval Sea Systems Command, which is responsible for introducing new equipment into the ships of the Navy.

Capt. Hughes joined Northrup Services following his retirement from the service in 1978.

Survivors include his wife, Carolyn, and two daughters, Nathalie and Catherine, all of Vienna, where the family lives; a son, Mark, a Marine Corps staff sergeant stationed in Brussels, Belgium; and three sisters, Rita Michaels of Odenton, Md., Dorothy Nayer of San Franicsco, and Lillian Usuda of Jensen Beach, Fla.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.