Control method and unit for controlling the clearance of a high-pressure turbine to reduce the effect of EGT overshoot

A control unit for controlling a clearance between tips of blades of a rotor of a high-pressure turbine of a gas turbine aircraft engine of an aircraft and a turbine ring of a casing surrounding said blades of the high-pressure turbine, the control unit comprising:

• means for estimating the clearance to be controlled;
• means for controlling a valve, the valve being configured to deliver an air stream towards said turbine ring based on said estimated clearance to be controlled;
• detection means configured to detect a transient phase of acceleration of the engine based on at least one parameter representative of the engine;
• receiving means configured to receive a data relating to an altitude of the aircraft;
• calculation means configured to determine data representative of a temperature of said rotor of the high-pressure turbine of the engine during the transient acceleration phase subsequent to determining data representative of a temperature of said rotor of the high-pressure turbine of the engine during a steady speed, and to calculate a relative temperature deviation between said temperature data determined during the transient acceleration phase and the temperature data determined during the steady speed;
• and
• control means configured to control an opening of the valve to deliver said air stream to the turbine ring at an opening level and for an opening time defined by a predefined altitude/relative temperature deviation lookup table, if the transient acceleration phase is detected and if said relative temperature deviation is greater than a predetermined minimum temperature deviation.