General. (1) An omission or incorrect action by a crewmember or maintenance personnel, or a mistake in requirements, design, or implementation. (2) An act that through ignorance, deficiency, or accident departs from or fails to achieve what should be done. Errors can be predictable and random. (3) Errors can also be categorized as primary or contributory. Primary errors are those committed by personnel immediately and directly involved with the accident. Contributory errors result from actions on the part of personnel whose duties preceded and affected the situation during which the results of the error became apparent. The difference between a computed, observed, or measured value or condition and true, specified, or theoretically correct value or condition. A mistake in engineering, requirement specification, or design, implementation, or operation which could result in a failure, and /or contributory hazard. There are four types of Human Errors: (1) Omission; (2) Commission; (3) Sequence; (4) Timing