FAA Powerplant Written Practice Test

What is the main function of a flywheel in an inertia starting system?

1. Store electrical energy

2. Store kinetic energy for cranking

3. Control engine temperature

4. Regulate fuel flow

The correct answer is: Store kinetic energy for cranking

The main function of a flywheel in an inertia starting system is to store kinetic energy for cranking the engine. When the flywheel spins, it accumulates kinetic energy due to its mass and rotational speed. This stored energy is then released to provide the necessary torque to start the engine. Inertia starting systems utilize this principle, where the momentum of the flywheel assists in turning the engine over during startup. The efficiency of the starting process is significantly improved because the energy stored by the flywheel can be released quickly, making it easier to crank the engine, even in conditions where higher starting torque is required. Other functions, such as storing electrical energy or regulating fuel flow, do not align with the flywheel's purpose in an inertia starting system. Engine temperature control is also unrelated to the mechanical role that a flywheel plays in aiding engine startups. The focus of a flywheel is purely mechanical, emphasizing energy storage and release for effective engine cranking.