Performs Operations & Maintenance (O&M) engineering involving maintenance, repair, upgrade, and operation of mechanical equipment and systems (such as HVAC, plumbing, and environmental controls) to infrastructure facilities, including utility systems, at a large and complex military installation utilizing a professional knowledge of mechanical engineering. Develops or oversees the preparation of plans, instructions, and specifications for the repair, modification, maintenance, and operational testing of existing and new types of systems with many component pieces of equipment, where the employee must search out and develop new or greatly modified approaches because available technical manuals or specifications are frequently inadequate.