Franklin Wolfgang Diederich, 77, who joined the Navy Department in 1976 and retired in 1994 as chief engineer for the program executive officer for space, communications and sensors, died of cancer Dec. 7 at the Hospice of Northern Virginia. He lived in Annandale.

Dr. Diederich was born in Germany and moved with his mother to New York City in 1937. He graduated from Cooper Union in 1943 with a bachelor's degree in mechanical engineering and from New York University in 1944 with a master's degree in aeronautical engineering. He received a doctorate in aeronautical engineering and mathematics from California Institute of Technology in 1954.

Except for the year he was at Cal Tech, Dr. Diederich was an engineer from 1945 to 1957 at the National Aeronautics and Space Administration's predecessor, the National Advisory Committee for Aeronautics in Hampton, Va. Among his areas of study at the advisory committee were aero-elasticity and aerodynamics.

After working a year at what became Northrop Grumman in California, Dr. Diederich was at AVCO Research and Development in Wilmington, Mass., first as a program manager on several defense systems, then as vice president of the office. He left in 1972 as vice president of engineering.

He spent four years at United Aircraft in Hartford as a research manager developing nuclear aircraft, antisatellite and space propulsion systems.

In 1994, Dr. Diederich received the Navy Department's Superior Civilian Service Award.

A violin prodigy in his youth -- at age 12 he was a soloist with the Dusseldorf Symphony Orchestra -- he played classical piano in recent years as a hobby.

Survivors include his wife of 50 years, Margaret Diederich of Annandale; two sons, Raymond Diederich of Gaithersburg and William Diederich of Columbus, Ohio; a daughter, Barbara Diederich of Lexington, Mass.; and four grandchildren.