A blade has an airfoil extending radially outwardly of a dovetail. The dovetail has edges that will be at circumferential sides of the blade when the blade is mounted within a rotor. A bottom surface of the dovetail will be radially inward when the rotor blade is mounted in a rotor, and is formed such that a circumferentially central portion of the bottom surface is radially thicker than are circumferential edges. A fan and a gas turbine engine are also described.

A method of cooling a shaft of a gas turbine engine includes moving a control valve towards a position that inhibits fluid flow from a high pressure air source to an air turbine starter and enables fluid flow from a blower motor to the air turbine starter, in response to a gas turbine engine shutdown. The method further includes operating the blower motor to provide air to the air turbine starter.

Aspects of the disclosure are directed to systems and methods for receiving operating state parameters associated with an operative state of an aircraft, determining a clearance value between a first structure of the engine and a second structure of the engine, where the clearance value is determined based on the operating state parameters and a passive clearance model that includes a specification of an uncertainty in the clearance value, determining that the clearance value deviates from a clearance target in an amount that is greater than a threshold, and engaging an active clearance control (ACC) mechanism based on the deviation.

A method of treating a component adapted for use in a gas turbine engine is described herein. The component may comprise ceramic matrix composite materials. The treatment to the ceramic matrix composite component may reduce or eliminate the wear or damage of crack propagation in the ceramic matrix composite component.

The present disclosure provides a device for controlling a variable section ejection nozzle of a turbojet engine nacelle of an aircraft. The device includes a calculator adapted to determine a position setpoint of the nozzle and a management system of the servo-control of the position of the variable nozzle depending on the flow rate of the fuel supplying the turbojet engine. The management system includes at least one instantaneous flow rate sensor of the fuel and a management unit which is designed to compare the flow rate measured by the flow rate sensor with a theoretical fuel flow rate depending on the parameters of the flight of the aircraft, to determine a correction value of the position of the nozzle depending on the comparison of the measured flow rate and the theoretical fuel flow rate, and to correct the position setpoint of the nozzle according to the correction value.

A method of bowed rotor start response damping for a gas turbine engine is provided. A spring rate and a damping characteristic of one or more bearing supports in the gas turbine engine are selectively modified while a shaft of the gas turbine engine rotates below a speed which is adversely affected by a bowed rotor condition of the gas turbine engine.

A bowed rotor start mitigation system for a gas turbine engine of an aircraft is provided. The bowed rotor start mitigation system includes a motoring system and a controller coupled to the motoring system and an aircraft communication bus. The controller is configured to determine at least one inferred engine operating thermal parameter from at least one aircraft-based parameter received on the aircraft communication bus. The motoring system is controlled to drive rotation of a starting spool of the gas turbine engine below an engine idle speed based on determining that the at least one inferred engine operating thermal parameter is within a preselected threshold.

A bowed rotor prevention system for a gas turbine engine is provided. The bowed rotor prevention system includes a thermoelectric generator system operable to produce electricity from waste heat of the gas turbine engine. The bowed rotor prevention system also includes a bowed rotor prevention motor operable to drive rotation of turbomachinery of the gas turbine engine using the electricity produced by the thermoelectric generator system.

A bowed rotor start mitigation system for a gas turbine engine is provided. The bowed rotor start mitigation system includes a variable position starter valve and a controller. The controller is operable to dynamically adjust the variable position starter valve to deliver a starter air supply to a starter to drive rotation of a starting spool of the gas turbine engine according to a dry motoring profile that continuously varies a rotor speed of the starting spool up to a point below a critical rotor speed.

A bowed rotor prevention system for a gas turbine engine of an aircraft is provided. The bowed rotor prevention system includes a gear train and a bowed rotor prevention motor. The gear train is coupled through an engine accessory to an engine accessory gearbox that is further coupled to a starting spool of the engine. The bowed rotor prevention motor is operable to drive rotation of the starting spool of the gas turbine engine through the gear train upon engine shutdown.