Mechanical drive system for an accessory gearbox

A mechanical drive system for an accessory gearbox (24) of a gas turbine engine is provided. The engine has a high-pressure drive shaft (12) and a low-pressure drive shaft (14). The mechanical drive system includes a first tower shaft (36), a second tower shaft (38), a first lay shaft (44), and a second lay shaft (46). The first tower shaft (36) is driven by the high-pressure drive shaft (12). The second tower shaft (38) is driven by the low-pressure drive shaft (14). The first lay shaft (44) is driven by the first tower shaft (36), and is connected to the accessory gearbox (24). The second lay shaft (46) is driven by the second tower shaft (38), and is connected to the accessory gearbox (24).