Alan S. Glendening, 56, an engineer who worked in the fields of petroleum, chemicals and aeronautics, died of cardiac arrest Sunday at the Carriage Hill nursing home in Arlington. He had multiple sclerosis.

Mr. Glendening was born in Paris, France, while his parents were vacationing there. He grew up in New York City and in 1944 graduated from Princeton University where he studied engineering, with a Phi Beta Kappa key.

He began his engineering career with the E.I. du Pont de Nemours Co. in Wilmington, Del., working on petroleum. He later worked on the company's heavy water atomic project on the Savannah River.

In 1957, he joined the Boeing company in Seattle, Washington. He was transferred to the Washington area in 1967 and worked on Boeing projects for the National Aeronautics and Space Administration. He left Boeing in 1972 and spent the next year working for consulting firms. In 1973, he retired for reasons of health.

For much of his career, Mr. Glendening was an engineering administrator. In 1971, he earned a master's degree in engineering administration at George Washington University, where he was elected to Tau Beta Pi, the honorary society for graduate students.

During his years in Seattle, he was a founder of the Crisis Center there and was its treasurer. He was a member of the Unitarian Church of Arlington.

Survivors include his wife, Jean M., of Arlington, three daughters, Lee G. Koss and Alicia B. Glendening, both of Alexandria, and Claire W. Glendening, of Arlington, and his father, Harold S. Glendening, of Orlando, Fla.