FAA Powerplant Written Practice Test

How are high voltage units triggered in a FADEC Powerlink ignition system?

1. From the ignition coil voltage

2. From the battery power

3. From the crankshaft position

4. By the magneto timing

The correct answer is: From the crankshaft position

In a FADEC (Full Authority Digital Engine Control) Powerlink ignition system, high voltage units are triggered based on the crankshaft position. This is crucial because the crankshaft position provides the precise timing needed for optimal ignition within the engine cycle. The FADEC system continuously monitors the crankshaft's rotational position, enabling it to determine the optimal moment to deliver high voltage to the ignition system, ensuring efficient and effective combustion. Using crankshaft position information allows the FADEC to synchronize ignition events with cylinder pressure and fuel injection, maximizing engine performance and minimizing emissions. This feedback mechanism is essential in modern engines, where precision and efficiency play significant roles in overall engine control. The other methods mentioned, such as ignition coil voltage, battery power, or magneto timing, do not serve the same purpose in this context. Ignition coil voltage pertains to the electrical response of the ignition system but does not initiate the triggering. Battery power provides energy but lacks the precision for timing ignition events. Magneto timing is typically associated with older ignition systems and is not applicable in the context of a FADEC-controlled engine.