FAA Powerplant Written Practice Test

How does high-tension ignition shielding reduce radio interference?

1. By grounding low frequency waves

2. By receiving and grounding high frequency waves from the magneto

3. By insulating the ignition leads

4. By eliminating all electromagnetic waves

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

High-tension ignition shielding reduces radio interference primarily by receiving and grounding high frequency waves generated by the magneto. In an aircraft engine ignition system, particularly those using magnetos, high voltage is delivered to the spark plugs through ignition leads. These leads can generate electromagnetic interference (EMI), particularly at high frequencies, which can affect radio communications and navigation systems. The shielding acts as a barrier that captures these high frequency signals and routes them to ground. By preventing these signals from radiating outward, the shielding minimizes the potential for interference with radios and other electronic equipment in the aircraft. This is critical for ensuring clear communication and reliable navigation. The other options do not effectively describe the function of high-tension ignition shielding. Grounding low frequency waves does not address the primary concern, which is the high frequency interference. Insulating the ignition leads is more about preventing electrical leakage rather than reducing EMI directly. Lastly, completely eliminating all electromagnetic waves is not feasible, as some level of EMI is inherent to electrical systems; the goal is to manage and minimize it instead.