Elliott Roosevelt, 80, a son of President Franklin D. Roosevelt, who wrote mystery novels as well as controversial memoirs about his parents during a career that included stints as a businessman and World War II officer and pilot, died yesterday in Scottsdale, Ariz.

Patricia Roosevelt, Mr. Roosevelt's fifth wife, to whom he had been married for 30 years, told the Associated Press that death was due to congestive heart failure.

Over the years, Mr. Roosevelt turned his hand to a variety of occupations and activities, including ranching, aviation, journalism, radio station management, advertising, public relations, finance, real estate sales and politics. He also served two years as mayor of Miami Beach.

During World War II, he accompanied his father to several historic international conferences, experiences that furnished material for a highly publicized and hotly debated postwar memoir.

"As He Saw It," setting forth the son's understanding of the father's views, appeared in 1946. Many reviewers took issue with his recounting and interpretation of the facts, but the book also won vigorous praise.

The appearance in 1973 of a new book, "An Untold Story: The Roosevelts of Hyde Park," plunged him into new public controversy and impaired relations among the late president's offspring.

The 1973 book was the first of three by Mr. Roosevelt and James Brough that, in addition to giving a behind-the-scenes look at the Roosevelt presidency, appeared to give new and detailed information on the private lives of Franklin and Eleanor Roosevelt.

"An Untold Story" was not the first book to venture into such areas, however; Mr. Roosevelt said he wrote it in response to what he viewed as misleading impressions created by such other works as Joseph Lash's "Eleanor and Franklin."

In addition, Mr. Roosevelt was the author of five well-received mystery works, period pieces in which the author's mother was the detective. The most recent, set in wartime London, was 1988's "Murder at the Palace."

Mr. Roosevelt was born in New York on Sept. 23, 1910, and graduated from his father's alma mater, the Groton School, in Massachusetts. After a year at the Hun School in New Jersey, he began working in advertising in New York.

Mr. Roosevelt, who was commissioned a captain in the Army Air Forces a year before the United States entered World War II, later became commander of an aerial reconnaissance wing that served in Europe.

He flew 89 missions, was wounded twice and promoted in February 1945 to brigadier general.

Of the four sons and one daughter born to Franklin and Eleanor Roosevelt, only James Roosevelt, a former member of Congress, survives. Anna Roosevelt Halstead, the eldest, died in 1975. John, the youngest brother, died in 1981. Franklin D. Roosevelt Jr. died two years ago.

In addition to his wife and brother, survivors include eight children, 21 grandchildren and three great-grandchildren.