What are the two alternate modes of the EEC?

What are the two alternate modes of the EEC?

• A. Soft alternate and hard alternate
• B. Manual and automatic
• C. Primary and secondary
• D. Mixed and idle

Answer: (A)

Two alternate modes describe how the engine’s electronic control can keep the engine running when the EEC isn’t fully healthy. In soft alternate, the EEC switches to backup logic and continues to control fuel flow, but with reduced capability and protections. You retain some automated behavior, but performance and safety limits are diminished, allowing the engine to be stabilized and operated to reach a safe location. In hard alternate, the EEC is bypassed entirely and the engine is governed by a separate, non-electronic (often mechanical/hydromechanical) control path. This provides basic, reliable operation with limited thrust range and no automated protections, sufficient to get you to a safe point or maintenance. The other options don’t reflect the specific fallback paths for engine control when the EEC fails, which is why soft alternate and hard alternate are the correct concepts.

Two alternate modes describe how the engine’s electronic control can keep the engine running when the EEC isn’t fully healthy. In soft alternate, the EEC switches to backup logic and continues to control fuel flow, but with reduced capability and protections. You retain some automated behavior, but performance and safety limits are diminished, allowing the engine to be stabilized and operated to reach a safe location.

In hard alternate, the EEC is bypassed entirely and the engine is governed by a separate, non-electronic (often mechanical/hydromechanical) control path. This provides basic, reliable operation with limited thrust range and no automated protections, sufficient to get you to a safe point or maintenance.

The other options don’t reflect the specific fallback paths for engine control when the EEC fails, which is why soft alternate and hard alternate are the correct concepts.