Increasing computer capability together with greater understanding of the learning process have resulted in improvements in the instructional capability of training devices. This complexity has spawned a great diversity in training device design approaches. Nowhere is this diversity more apparent (and often less understood), than in the design of maintenance trainers. The military is currently procuring both lock-step and free-play maintenance trainers at significant cost. Lock-step trainers lead the trainee through prescribed maintenance training in a pre-determined, pre-programmed fashion. Free-play trainers have no prescribed maintenance path. Trainees, therefore, are free to perform any set of procedures in any sequence. The device simulates real equipment in every way possible and will not automatically freeze when a mistake is made. Unfortunately, the purposes of the two device types are often confused. Decreased training effectiveness and increased cost are commonly the result.

This paper examines differences between lock-step and free-play maintenance trainers and explores appropriate uses of each. Major issues which should be considered when determining how much free-play and/or lock-step to design into a training device are discussed in the paper. These issues include the expertise of the trainee; complexity of the tasks to be learned; the number and skill levels of the instructors; the nature of the actual operational equipment; and the cost of procurement.