What drives the accessory gear box?

What drives the accessory gear box?

• A. Engine alternator
• B. Gas Generator (at variable speed)
• C. NP
• D. NG

Answer: (B)

The accessory gear box is powered by the gas generator portion of the engine through the accessory drive. In a UH-60’s turboshaft, all the engine-driven accessories (fuel pump, hydraulic pump, generators, etc.) get their drive from the high-pressure gas generator via a drive shaft. Because the gas generator speed varies with throttle and engine load, the accessory gear box input is at a variable speed. The power turbine (NP) drives the rotor, not the AGB, and the engine’s alternator is a load on the AGB, not the driver. So the correct concept is that the accessory gear box is driven by the gas generator, at variable speed.

The accessory gear box is powered by the gas generator portion of the engine through the accessory drive. In a UH-60’s turboshaft, all the engine-driven accessories (fuel pump, hydraulic pump, generators, etc.) get their drive from the high-pressure gas generator via a drive shaft. Because the gas generator speed varies with throttle and engine load, the accessory gear box input is at a variable speed. The power turbine (NP) drives the rotor, not the AGB, and the engine’s alternator is a load on the AGB, not the driver. So the correct concept is that the accessory gear box is driven by the gas generator, at variable speed.