Louise Patten's grandfather was second officer. He told his wife that the steering officer panicked and inadvertently steered into an iceberg in April of 1912 because he wasn't used to the new steering system. More than 1,500 people died.
Patten says her grandfather felt that admitting error would have sparked lawsuits.
"I'm the only living person who knows why Titanic sank. It was a terrible mistake," said Patten.
She says the ship sank so fast because the owner ordered the captain to continue moving, instead of cutting the engines.
Patten's statements coincide with the release of her new novel about the Titanic.