Elliott Roosevelt, a World War II Air Corps general, a breeder of Arabian horses and an author whose works included a series of mystery novels that cast his mother, the First Lady, as an amateur detective, died yesterday at his home in Scottsdale, Ariz. He was 80 years old.

Mr. Roosevelt died of congestive heart failure, his wife, the former Patricia Peabody, said.

The second child of President Franklin Delano Roosevelt and Eleanor Roosevelt, Elliot Roosevelt began his writing career in 1946 with "As He Saw It," a best-selling account of his experiences at his father's side during five historic wartime summit conferences.

His trilogy of "tell-all" books about life behind the scenes in the Roosevelt White House and at the family home in Hyde Park, N.Y., caused a rift in the family in the early 1970's, leading his sister and three brothers to publicly disavow the books. A book he wrote in 1983, "The Conservators," was a statement of his philosophy about the survival of the planet.

Mr. Roosevelt, also a great-nephew of Theodore Roosevelt, was born in New York City on Sept. 23, 1910. He attended the Groton School, as had his father, but broke a family tradition by not going on to Harvard. Instead, he turned to advertising and radio.