US Patent 10415421 Thrust rating dependent active tip clearance control system

Disclosed is an active tip clearance control system (ATCCS) for a gas turbine engine, having an electronically controlled regulating valve directing cooling airflow to a turbine case, and an engine electronic control (EEC), controlling the electronically controlled regulating valve, wherein the EEC controls the electronically controlled regulating valve to regulate cooling airflow according to a selected target blade tip clearance schedule, and wherein the selected target blade tip clearance schedule is selected before or after an engine cycle, from of a plurality of target blade tip clearance schedules, each correlating to one of a plurality of thrust rating applications for the engine.