Blade pitch control system

Abstract

A method of operating a blade pitch change system of a gas turbine engine and its arrangement, the system comprising a blade, an actuator, a pressurised fluid system and a control system that regulates pressurised fluid to the actuator to control its position and thereby the blade's pitch; the blade pitch change system operates in a forward thrust mode and a reverse thrust mode, the control system comprises a main pitch control valve and a first reverse blade control valve through which the pressurised fluid passes. The method comprises the steps of a) continuously varying the main control valve to change the blade's pitch within the forward thrust mode at a first rotational rate, b) switching the first reverse blade control valve on to change the blades' pitch between the forward thrust mode and the reverse thrust mode at a second rotational rate that is greater than the first rotational rate.

Dependencies are inferred from the claim text.