On the engine panel aft overhead, the indicators ON and ALTN are visible when the EEC has automatically changed to which mode?

On the engine panel aft overhead, the indicators ON and ALTN are visible when the EEC has automatically changed to which mode?

• A. Normal
• B. Soft alternate
• C. Maintenance
• D. Cold start

Answer: (B)

When the engine electronic control detects a fault but can still run safely, it automatically switches to a degraded operating state called Soft Alternate. In this mode the EEC uses alternate logic to keep the engine running with protections and reduced performance, rather than shutting the engine down. The presence of both ON and ALTN signals shows the system is powered and operating in this alternate, degraded mode. If it were in Normal mode there wouldn’t be the ALTN indication, and Maintenance or Cold Start scenarios use different indicators or require manual procedures rather than an automatic soft alternate transition.

When the engine electronic control detects a fault but can still run safely, it automatically switches to a degraded operating state called Soft Alternate. In this mode the EEC uses alternate logic to keep the engine running with protections and reduced performance, rather than shutting the engine down. The presence of both ON and ALTN signals shows the system is powered and operating in this alternate, degraded mode. If it were in Normal mode there wouldn’t be the ALTN indication, and Maintenance or Cold Start scenarios use different indicators or require manual procedures rather than an automatic soft alternate transition.