Gas turbine start system to enable rotor thermal stabilization with backup bleed bypass cooling mode

1. A system comprising:

a starter air valve in fluid communication with an air turbine starter to drive motoring of a gas turbine engine responsive to a compressed air flow from a compressed air source;

a manual override operably connected to the starter air valve, the manual override is operable to open the starter air valve a select percentage by moving the manual override to a detent engaged position; and

a pressure regulating bleed valve in fluid communication with the starter air valve, the pressure regulating bleed valve operable to bleed a portion of the compressed air flow to regulate a motoring speed of the gas turbine engine in response to detection of the manual override in a detent engaged position,

wherein the manual override further comprises a detent plate having a detent hole and a detent ball opposite the detent plate, the detent ball is operable to engage the detent hole when the manual override is pushed downward and rotated to the detent engaged position.

2. The system as in claim 1 , wherein the pressure regulating bleed valve is located downstream from the starter air valve.

3. The system as in claim 1 , wherein the manual override is moved to the detent engaged position by rotating the manual override a selected angular rotation.

4. The system as in claim 1 , wherein the manual override further comprises a first biasing mechanism operable to prevent the detent ball from engaging the detent hole unless the manual override is pushed downward and rotated to the detent engaged position.

5. The system as in claim 1 , wherein the compressed air source is an auxiliary power unit, a ground cart, or a cross-engine bleed.

6. A system of an aircraft, the system comprising:

an air turbine starter coupled to a gearbox;

a starter air valve in fluid communication with an air turbine starter to drive motoring of a gas turbine engine responsive to a compressed air flow from a compressed air source;

a pressure regulating bleed valve in fluid communication with the starter air valve; and

a manual override operably connected to the starter air valve, the manual override is operable to open the starter air valve a select percentage by moving the manual override to a detent engaged position; and

a computer controller program to actuate the pressure regulating bleed valve to bleed a portion of the compressed air flow to regulate a motoring speed of the gas turbine engine in response to detection of the manual override in a detent engaged position,

wherein the manual override further comprises a detent plate having a detent hole and a detent ball opposite the detent plate, the detent ball is operable to engage the detent hole when the manual override is pushed downward and rotated to the detent engaged position.

7. The system as in claim 6 , wherein the pressure regulating bleed valve is located downstream from the starter air valve.

8. The system as in claim 6 , wherein the manual override is moved to the detent engaged position by rotating the manual override a selected angular rotation.

9. The system as in claim 6 , wherein the manual override further comprises a first biasing mechanism operable to prevent the detent ball from engaging the detent hole unless the manual override is pushed downward and rotated to the detent engaged position.

10. The system as in claim 6 , wherein the compressed air source is an auxiliary power unit, a ground cart, or a cross-engine bleed.

11. A method comprising:

detecting, by a computer processor, a manual override of a starter air valve in a detent engaged position, wherein the starter air valve is in fluid communication with an air turbine starter to drive motoring of a gas turbine engine responsive to a compressed air flow from a compressed air source; and

controlling, by the computer processor, a pressure regulating bleed valve in fluid communication with the starter air valve to bleed a portion of the compressed air flow to regulate a motoring speed of the gas turbine engine in response to detection of the manual override in a detent engaged position;

wherein the manual override is operable to open the starter air valve a select percentage by moving the manual override to a detent engaged position.

12. The method as in claim 11 , wherein the pressure regulating bleed valve is located downstream from the starter air valve.

13. The method as in claim 11 , wherein the manual override is moved to the detent engaged position by rotating the manual override a selected angular rotation.

14. The method as in claim 11 , wherein the manual override further comprises a detent plate having a detent hole and a detent ball opposite the detent detent plate, the detent ball is operable to engage the detent hole when the manual override is pushed downward and rotated to the detent engaged position.

15. The method as in claim 11 , wherein the manual override further comprises a first biasing mechanism operable to prevent the detent ball from engaging the detent hole unless the manual override is pushed downward and rotated to the detent engaged position.

16. The method as in claim 11 , wherein the compressed air source is an auxiliary power unit, a ground cart, or a cross-engine bleed.