Failure can be the source of useful information. This class presents case studies of failures and illustrates what went wrong, what we can learn, and what we can do to avoid them. The case studies include Comet ” the first jet-engine airliner that tested the limits of human knowledge; Therac-25 ” a development nightmare; Chernobyl ” a study in human expertise, experience, and arrogance; Ariane 5 ” importance of thorough test and review; product recalls; and Sidewinder missile ” 50 years of success.