A gas turbine startup method and device wherein low-pressure, medium-pressure, and high-pressure air bleed flow paths supply compressed air bled from low-pressure, medium-pressure, and high-pressure air bleed chambers, respectively, of a compressor as cooling air to a turbine. Low-pressure, medium-pressure, and high-pressure exhaust flow paths discharge the compressed air in the low-pressure, medium-pressure, and high-pressure air bleed flow paths, respectively to the turbine exhaust system, and the low-pressure, the medium-pressure, and the high-pressure exhaust flow paths are provided respectively with a low-pressure exhaust valve, a medium-pressure exhaust valve, and a high-pressure exhaust valve. When the gas turbine starts up, the high-pressure exhaust valve is opened before the startup state of the gas turbine reaches a region in which rotation stall occurs.

A system for motoring a gas turbine engine of an aircraft is provided. The system includes an air turbine starter operable to drive rotation of a starting spool of the gas turbine engine and a starter air valve operable to deliver compressed air to the air turbine starter in response to the starter air valve being open. The system also includes a metered orifice coupled in a bypass configuration around the starter air valve to deliver a reduced amount of the compressed air to the air turbine starter while the starter air valve is closed. The reduced amount of the compressed air delivered to the air turbine starter limits a motoring speed of the gas turbine engine below a resonance speed of the starting spool of the gas turbine engine.

A system for motoring a gas turbine engine of an aircraft is provided. The system includes an air turbine starter operable to drive rotation of a starting spool of the gas turbine engine and a starter air valve operable to deliver compressed air to the air turbine starter in response to the starter air valve being open. The system also includes a metered orifice coupled in a bypass configuration around the starter air valve to deliver a reduced amount of the compressed air to the air turbine starter while the starter air valve is closed. The reduced amount of the compressed air delivered to the air turbine starter limits a motoring speed of the gas turbine engine below a resonance speed of the starting spool of the gas turbine engine.

A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed, where the controller modulates a duty cycle of the discrete starter valve via pulse width modulation.

A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed, where the controller modulates a duty cycle of the discrete starter valve via pulse width modulation.

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 based on at least one aircraft-based parameter received on the aircraft communication bus, where the at least one inferred engine operating thermal parameter is based on data describing a history of the aircraft before an engine shutdown. 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 range.

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 based on at least one aircraft-based parameter received on the aircraft communication bus, where the at least one inferred engine operating thermal parameter is based on data describing a history of the aircraft before an engine shutdown. 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 range.

A starter for a gas turbine engine includes a rotor shaft rotatable about an axis and includes an inner bore extending from an axial end of the rotor shaft with respect to the axis. A sun gear is on the rotor shaft. A lock nut is received against an axial end face of the sun gear and threadedly engaged with an outer diameter of the rotor shaft. A retainer is positioned to bias the nut against the axial end face and includes a projection portion threadedly engaged with the rotor shaft in the inner bore. A bolt through the projection portion is threadedly engaged with the rotor shaft.

A starter for a gas turbine engine includes a rotor shaft rotatable about an axis and includes an inner bore extending from an axial end of the rotor shaft with respect to the axis. A sun gear is on the rotor shaft. A lock nut is received against an axial end face of the sun gear and threadedly engaged with an outer diameter of the rotor shaft. A retainer is positioned to bias the nut against the axial end face and includes a projection portion threadedly engaged with the rotor shaft in the inner bore. A bolt through the projection portion is threadedly engaged with the rotor shaft.

A system for bleeding air from a core flow path of a gas turbine engine is disclosed. In various embodiments, the system includes a bleed valve having a bleed valve inlet configured to receive a bleed air from a first access point to the core flow path and a bleed valve outlet; and an air motor having a first air motor inlet configured to receive the bleed air from the bleed valve outlet and a first air motor outlet configured to exhaust the bleed air, the air motor configured to pump the bleed air from the core flow path of the gas turbine engine.