Final answer:
The Air Turbine Starter (ATS) dry motors a turbine engine's N2, but a specific RPM value cannot be determined without further information. An ATS typically brings the engine to 20-30% of N2 RPM for adequate airflow without fuel, in preparation for engine start.
Step-by-step explanation:
The Air Turbine Starter (ATS) is a device designed to start the engine of an aircraft by accelerating its main engine to a certain RPM (rotations per minute) using compressed air. The specific rotation rate up to which an ATS can dry motor an turbine engine's N2 depends on the engine design and the ATS itself. While the question seems to ask for a numeric value, it does not provide one within the details given. Therefore, it's impossible to give a definitive answer. However, as general knowledge, an ATS might be capable of motoring an engine up to anywhere from 20-30% of the N2 RPM, depending on the engine and starter specifications.
It's crucial for an ATS to be able to rotate the engine and achieve adequate airflow without the use of fuel (dry motoring) before starting, which can prevent potential damage due to oil contamination or insufficient lubrication during start-up. Pilots and maintenance personnel rely on the ATS to bring the engine to a sufficient RPM level for ignition and a successful engine start.