Auxiliary drive bowed rotor prevention system for a gas turbine engine

1. A bowed rotor prevention system for a gas turbine engine of an aircraft, the bowed rotor prevention system comprising:

an engine accessory gearbox;

a gear train comprising an epicyclic gear set coupled to the engine accessory gearbox, wherein the epicyclic gear set is mounted to a manual crank pad of the engine accessory gearbox and a housing of the epicyclic gear set comprises an access port to engage a cranking tool with the manual crank pad while the engine accessory gearbox remains coupled to the epicyclic gear set; and

a bowed rotor prevention motor operable to drive rotation of a starting spool of the gas turbine engine through the gear train at a substantially constant speed upon engine shutdown, the bowed rotor prevention motor operable to be powered by an energy storage source.

2. The bowed rotor prevention system as in claim 1 , wherein the gear train comprises a back-drive preventer that isolates the bowed rotor prevention motor from rotatable components of the gas turbine engine to inhibit the bowed rotor prevention motor from being back-driven.

3. The bowed rotor prevention system as in claim 2 , wherein the back-drive preventer is a clutch.

4. The bowed rotor prevention system as in claim 1 , wherein the bowed rotor prevention motor is an electric motor and the energy storage source is a battery or a capacitor.

5. The bowed rotor prevention system as in claim 4 , wherein the energy storage source is rechargeable by a generator on an aircraft electrical system.

6. The bowed rotor prevention system as is claim 4 , wherein the bowed rotor prevention motor is further operable to be driven by electrical power from an auxiliary energy source.

7. The bowed rotor prevention system as in claim 1 , wherein the bowed rotor prevention motor is further operable to drive rotation of the starting spool until a bowed rotor prevention shutdown request is detected, wherein the bowed rotor prevention shutdown request is detected based on one or more of: a detected opening of a nacelle of the gas turbine engine, a shutoff switch accessible to maintenance personnel on the nacelle or the gas turbine engine, a computer interface command on the aircraft, a detected fault condition, a time limit, a temperature limit, or a start command of the gas turbine engine.

8. The bowed rotor prevention system as in claim 1 , wherein the epicyclic gear set has a reduction ratio between 100:1 and 10,000:1.

9. The bowed rotor prevention system as in claim 1 , further comprising a delay circuit operable to delay activation of the bowed rotor prevention motor upon engine shutdown.

10. A gas turbine engine of an aircraft, the gas turbine engine comprising:

a starting spool coupled to an engine accessory gearbox;

a gear set coupled to the engine accessory gearbox, wherein the gear set is mounted to a manual crank pad of the engine accessory gearbox and a housing of the gear set comprises an access port to engage a cranking tool with the manual crank pad while the engine accessory gearbox remains coupled to the gear set; and

a bowed rotor prevention motor operable to drive rotation of the starting spool through the gear set and the engine accessory gearbox at a substantially constant speed upon engine shutdown, the bowed rotor prevention motor operable to be powered by an energy storage source.

11. The gas turbine engine of claim 10 , wherein the bowed rotor prevention motor is further operable to drive rotation of the starting spool until a bowed rotor prevention shutdown request is detected, wherein the bowed rotor prevention shutdown request is detected based on one or more of: a detected opening of a nacelle of the gas turbine engine, a shutoff switch accessible to maintenance personnel on the nacelle or the gas turbine engine, a computer interface command on the aircraft, a detected fault condition, a time limit, a temperature limit, or a start command of the gas turbine engine.

12. The gas turbine engine of claim 10 , wherein the gear set is an epicyclic gear set, and the gear set comprises an over-running clutch to prevent the bowed rotor prevention motor from being back-driven.

13. The gas turbine engine of claim 10 , wherein the bowed rotor prevention motor is coupled to the housing of the gear set.

14. A method for bowed rotor prevention for a gas turbine engine of an aircraft, the method comprising:

engaging a bowed rotor prevention motor with a starting spool of the gas turbine engine through a gear train comprising an epicyclic gear set coupled to an engine accessory gearbox, wherein the epicyclic gear set is mounted to a manual crank pad of the engine accessory gearbox and a housing of the epicyclic gear set comprises an access port to engage a cranking tool with the manual crank pad while the engine accessory gearbox remains coupled to the epicyclic gear set; and

driving rotation of the starting spool by the bowed rotor prevention motor through the gear train at a substantially constant speed upon engine shutdown, the bowed rotor prevention motor operable to be powered by an energy storage source.

15. The method as in claim 14 , wherein the bowed rotor prevention motor is an electric motor and the energy storage source is a battery or a capacitor, and the method further comprises:

recharging the energy storage source using a generator on an aircraft electrical system.

16. The method as in claim 14 , further comprising:

driving rotation of the starting spool until a bowed rotor prevention shutdown request is detected, wherein the bowed rotor prevention shutdown request is detected based on one or more of: a detected opening of a nacelle of the gas turbine engine, a shutoff switch accessible to maintenance personnel on the nacelle or the gas turbine engine, a computer interface command on the aircraft, a detected fault condition, a time limit, a temperature limit, or a start command of the gas turbine engine.

17. The method as in claim 14 , further comprising:

delaying activation of the bowed rotor prevention motor upon engine shutdown through a delay circuit.