Which of the following statements accurately identifies a major component of the accessory gearbox?

• A. N1 gear train and N2 gear train
• B. N2 gear train and N3 gear train
• C. N1 gear train and N3 gear train
• D. N3 gear train and N4 gear train

Answer: (A)

The basic idea is that the accessory gearbox is driven by the engine spools through internal gear trains, delivering power to items like pumps and the starting gear. The two primary drives feeding the gearbox are the N1 gear train and the N2 gear train. These two spools provide the necessary power and speed range for the accessories throughout engine start and operation, with the gear reduction letting pumps and starters run at usable speeds and with enough torque. In this common arrangement, N3 and N4 aren’t the standard drives feeding the accessory gearbox, so the two gears trains tied to N1 and N2 are the major components inside the gearbox.