The arrangement of control air, code 356975, is an important pneumatic system of the MAN L21/31 engine designed to distribute and regulate compressed air required for the operation of associated control devices, actuators, valves, and other pneumatically operated components. Depending on the specific engine configuration, the control air arrangement may include pipes, fittings, pressure-regulating devices, filters, valves, and connections that work together to ensure a stable and reliable supply of compressed air at the required operating pressure. During engine operation, the system must maintain adequate air pressure, clean internal passages, and leak-tight connections to ensure accurate and responsive operation of the associated control functions. Moisture, oil contamination, pressure fluctuations, air leakage, or restrictions within the pneumatic circuit can adversely affect control performance and operational reliability. During maintenance and overhaul, the arrangement should be inspected for corrosion, damaged piping, loose connections, leakage, contamination, and malfunctioning control components. By ensuring dependable distribution and management of compressed control air, the arrangement contributes to precise pneumatic actuation, stable engine operation, improved operational safety, and the long-term reliability of the MAN L21/31 engine.