If asked which condition triggers FADEC channel activity, which option is correct?

• A. Engine overspeed
• B. Engine idle
• C. Engine start only
• D. Engine off

Answer: (A)

Engine protection through FADEC channels activates when the system detects a condition outside normal limits. Engine overspeed is a high-risk situation where the rotational speed exceeds the maximum allowed. The FADEC uses sensor data to confirm the overspeed and immediately engages its protection logic, trimming fuel flow and adjusting the commanded speed to bring N1/N2 back within safe bounds. This rapid channel action is designed to prevent damage to the compressor and other engine components, even if one control path has a fault.

Idle, start, and off are normal operating states or phases. They don’t represent abnormal conditions that require the protective channel activation, so they don’t trigger the same channel response as an overspeed event.