Gas turbine engine starter reduction gear train with stacked planetary gear systems

An integrated starter and core-turning system for a gas turbine engine, the integrated starter and core-turning system comprising:

• a starter comprising a starter gear train that interfaces to an accessory gearbox of the gas turbine engine;
• and
• a reduction gearbox comprising:
• a reduction gear train operable to drive rotation of the starter gear train, the reduction gear train comprising:
• a starter interface gear operably connected to the starter gear train;
• a core-turning clutch operably connected to the starter interface gear;
• and
• a plurality of stacked planetary gear systems operably connected to the core-turning clutch and a core-turning input;
• and
• a mounting pad comprising an interface to couple a core-turning motor to the core-turning input of the reduction gear train.

A method of installing a reduction gear train through a starter of a gas turbine engine, the method comprising:

• arranging a plurality of stacked planetary gear systems of the reduction gear train in a reduction gearbox;
• coupling the stacked planetary gear systems with a core-turning clutch operably connected to a starter interface gear;
• engaging the starter interface gear with a starter gear train of the starter that interfaces to an accessory gearbox of the gas turbine engine;
• aligning a drive shaft coaxially with the stacked planetary gear systems and the core-turning clutch;
• and
• coupling a core-turning motor with the reduction gear train at a core-turning input of the drive shaft.