This is a fuel injection servo (RSA-10AD1) designed for Lycoming fuel-injected aircraft engines, particularly IO-540 and AEIO-540 series. It precisely meters and regulates fuel flow based on airflow and throttle input, ensuring optimal fuel-air mixture across all engine operating ranges. The unit is dynamically tested from idle to full throttle, providing accurate fuel delivery, improved engine performance, and reliable operation in aviation environments. It is a critical component of the aircraft fuel injection system, commonly supplied as new, rebuilt, or overhauled units.