FAA Powerplant Written Practice Test

What is used to drive a supercharger?

1. Electric motor

2. Gear train from the crankshaft

3. Hydraulic system

4. Turbocharger exhaust gases

The correct answer is: Gear train from the crankshaft

A supercharger is typically driven by a gear train connected directly to the crankshaft of the engine. This direct connection allows the supercharger to compress the air entering the engine, thus increasing its density and the overall power output of the engine. The gear train ensures that the supercharger operates in tandem with the engine's speed, providing optimal performance and boosting the engine’s power at low RPMs. In contrast, the other options are not typically how superchargers are powered. An electric motor may be used for other types of systems, but it is not standard for superchargers. A hydraulic system might power other accessories or components in some applications, but again, it's not a common method for driving superchargers. Turbochargers rely on exhaust gases to operate, which is a different mechanism entirely; they utilize the engine's exhausted gases to spin a turbine that compresses incoming air, rather than being connected to the crankshaft like a supercharger.