FAA Powerplant Written Practice Test

How does high-tension ignition shielding help reduce radio interference?

1. By amplifying electrical signals

2. By blocking low-frequency signals

3. By receiving and grounding high frequency waves

4. By isolating the ignition system from the rest of the aircraft

The correct answer is: By receiving and grounding high frequency waves

High-tension ignition shielding is designed to help mitigate radio interference primarily by receiving and grounding high frequency waves. This is important because ignition systems operate at high voltages and can generate electromagnetic interference (EMI) due to the rapid switching of current, especially in magneto-type ignition systems. When high-frequency electromagnetic waves are generated, they can radiate out and interfere with the operation of radio and communication equipment onboard an aircraft. The shielding acts as a barrier that can capture these waves and redirect them to the aircraft's ground, effectively preventing them from radiating into the environment. This grounding of high-frequency signals is crucial in maintaining clear communication and ensuring that avionics function correctly without disturbances caused by the ignition system. In contrast, while blocking low-frequency signals and isolating the ignition system can contribute to reducing interference, they do not directly address the mechanisms by which high-frequency signals cause disruption. Amplifying electrical signals is counterproductive in this context, as it could potentially increase interference rather than reduce it. Thus, the focus on receiving and grounding high-frequency waves makes this approach effective in minimizing radio interference from high-tension ignition systems.