SOUTHAMPTON, England, Jan. 11 (Reuters)--- Authorities today ordered an inquest into the death of Fred Fleet, a lookout on the liner Titanic, who hanged himself yesterday two weeks after his wife's death.The body of Mr. Fleet, who was 76 years old, was found hanging from a post in the garden of his Southampton home. The police said he had been depressed since the death of his wife, 74.

Mr. Fleet was one of the principal witnesses at an inquiry on the sinking of the Titanic. The luxury liner, on her maiden voyage to New York, struck an iceberg in the North Atlantic on the night of April 14, 1912, and sank with a loss of 1,513 lives.

Mr. Fleet testified that the White Star liner, which at the time was considered unsinkable, was almost on top of the iceberg when he gave the warning: "We are in danger---iceberg right ahead."

Within two hours and 40 minutes the 46,382-ton liner, with lifeboats for only half her passengers, was on her way to the bottom. Only 750 persons were saved.

The night was clear and free of fog, Mr. Fleet testified. He said he could have averted the disaster if he had been equipped with field glasses.

He was part of the crew of one of the ship's lifeboats and was picked up three hours later by the liner Carpathia.

The disaster did not deter him from going back to sea. He spent the next 24 years on various vessels before taking a job on shore during the depression.

He preserved his seaman's discharge book, in which his Titanic experience was recorded in two terse sentences: "Discharged at sea. Destination intended for New York."

Some criticism for the heavy loss of life among the Titanic's passengers was aimed at Capt. Stanley Lord, master of the liner Californian, which was stopped in ice only a few miles away when the Titanic sank.

Courts of inquiry, held in Britain and the United States, censured Captain Lord for failing to appreciate the nature of rocket signals reported to him. He contended that the Californian could not have reached the scene of the disaster ahead of the Carpathia, the first vessel to do so.

Mr. Lord died in 1962, without gaining a rehearing on his role.