Proper application of human factors criteria in designing ships reduces the probability of human error in operations and maintenance. Designers must consider the human being in the system and design for safe and efficient operation. This report describes the study conducted on the MCM-3 engineering scale models of the machinery spaces at Peterson Builders. It is intended to be used as a reference to help with the understanding of engineering scale models and their application for human engineering. The trend in the design of U.S. Navy ships is to incorporate human engineering into the design and ensure adequate consideration of human factors. The U.S. Navy requires scale models of the machinery spaces to be built for design and to be used to accomplish human engineering studies. The reduced scale model permits human engineering feedback during the design process. The scale model is a powerful tool to achieve systems integration and meet operability and maintainability objectives. This report identifies what can be done and how to plan to do it.