FAA Powerplant Written Practice Test

What drives accessories such as electric generators on turbine powered aircraft?

1. High pressure compressor directly

2. Low pressure compressor directly

3. Reduction gearbox from the high pressure compressor

4. Directly from the turbine exhaust

The correct answer is: Reduction gearbox from the high pressure compressor

In turbine-powered aircraft, accessories like electric generators are typically driven through a reduction gearbox connected to the high-pressure compressor. This gearbox allows the electric generator to operate at its optimal speed, often much lower than the rotational speed of the high-pressure compressor. This setup is efficient as it provides a constant and reliable source of mechanical power to the generator, regardless of the varying operational conditions of the engine. The high-pressure compressor operates at high RPMs, and using a reduction gearbox makes it feasible to power accessories without compromising their functional integrity. The other options do not align with how power is usually transmitted to these accessories; therefore, they are not practical solutions for driving generators in turbine engines.